Artificial lightweight aggregate made from alternative and waste raw materials, hardened using the hybrid method

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A huge amount of this material is used in construction and architecture. For the most part, lightweight construction aggregates are obtained from natural resources such as clay raw materials that have the ability to swell at high temperatures. Resources of these clays are limited and not available everywhere. Therefore, opportunities are being sought to produce lightweight artificial aggregates that have interesting performance characteristics due to their properties. For example, special preparation techniques can reduce or increase the water absorption of such an aggregate depending on the needs and application. The production of artificial lightweight aggregate using various types of waste materials is environmentally friendly as it reduces the depletion of natural resources. Therefore, this article proposes a method of obtaining artificial lightweight aggregate consolidated using two methods: drum and dynamic granulation. Hardening was achieved using combined methods: sintering and hydration, trying to maintain the highest possible porosity. Waste materials were used, such as dust from construction rubble and residues from the processing of PET bottles, as well as clay from the Bełchatów mine as a raw material accompanying the lignite overburden. High open porosity of the aggregates was achieved, above 30%, low apparent density of 1.23 g/cm 3 , low leachability of approximately 250 µS. The produced lightweight aggregates could ultimately be used in green roofs. Physical sciences/Engineering/Civil engineering Earth and environmental sciences/Environmental sciences Physical sciences/Materials science artificial lightweight aggregate green roofs waste materials recycling water retention capacity Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 1. Introduction Lightweight aggregate (LWA) is defined as solid substance with an apparent density of less than 2.0 g/cm 3 and a bulk density of less than 1.2 g/cm 3 (EN 13055:2016). LWAs are porous and often granular materials that are widely used in architecture, landscaping and geotechnics. The porosity of these materials can be either open or closed, which affects their applicability. For example, aggregates with open porosity can provide effective drainage but also micro water retention. Furthermore, they can provide better sound absorption and thermal insulation. Lightweight aggregates can be divided into the following categories (Kumar 2010, Franus 2015, Alqahtani 2019 ): naturally occurring raw materials that require further processing, such as clays and intrusive shales and vermiculite; naturally occurring raw materials that do not require processing, such as pumice stone, foamed lava, volcanic tuff and porous limestone. industrial wastes such as sintered fly ash or foamed blast furnace slag. The most commonly used artificial aggregate in many industries is sintered fly ash. The use of lightweight aggregate in concrete has gained popularity due to its low density, good thermal conductivity and strength, environmental friendliness and many other advantages. (George 2020 , Sun 2021). A global environmental problem due to the use of large amounts of natural resources is generated by the construction industry. Most of the aggregates used in this industry are obtained from natural resources. There is a continuous increase in the production of construction materials and therefore non-renewable natural resources are diminishing at an accelerating rate due to the high demand for their use in concrete production. Of course, for heavy-duty, high-strength and cover concretes, the use of quality natural aggregates appears to be essential. However, modern construction is moving away from oversized heavy structures. The development of the manufacture of artificial of lightweight materials such as lightweight aggregate will help minimize the use of natural resources. Lightweight aggregate is significantly different from conventional aggregate. The obtained modifications may bring benefits and new challenges for designers for many reasons, for example weight reduction, improved acoustic or thermal properties, drainage or filtration capabilities. (Kumar 2010, Alqahtani 2019 , Hao 2022). Undoubtedly, the consumption of construction aggregates depletes natural resources and poses a direct threat to the environment. Due to the increasing expansion of construction, resources of natural aggregates are rapidly decreasing. There is a local shortage of resources that requires proper use for sustainable development (Kozioł 2016. Khan 2023). Bibliographic research conducted by the authors shows that the dominant issue in the field of waste and recycled materials is the technology of building materials, and in particular the technology of concrete. It can be said that these issues are present in virtually every scientific and economic field. Starting from mineral and biotic resources, through broadly understood chemical and physical sciences, to geotechnics (Stempkowska 2023). An interesting direction of use of waste materials are fired materials such as bricks, tiles, lightweight aggregates (Danish 2022, Izak 2023,, Simao 2023, Singh 2023). However, the authors of the above publications point out the difficulties in using waste materials. Despite homogenization processes, mineral waste is characterized by low composition stability and the presence of soluble compounds. Such compounds may cause efflorescence on the surface or increased leachability of harmful substances, which causes functional defects. Natural sand can be replaced using by-products from coarse aggregate production, which are widely available, cheaper and reduce the extraction of natural sand (Altuki 2022). Additionally, manufactured sand has become a popular choice to replace natural sands because it is often extracted from streambeds and sand extraction is considered environmentally harmful (Franus 2015). In addition, the produced sand, which is made from hard igneous, sedimentary or metamorphic rocks, can be produced locally, reducing transportation costs. The demand for aggregates with a coarser fraction is different. Such materials, obtained from waste raw materials, must be integrated. They can be obtained in several ways, such as: cold consolidation ~ 25°C (cold setting, cementation, geopolymerization) (Rehman 2019, Zafar 2021) autoclaving to about 200°C sintering, at temperatures above 900°C (Hao 2022). Generally, lightweight aggregate produced at, for example, ~ 1200°C provides the best mechanical properties, but deteriorates its porosity. To obtain the most favorable properties of artificial aggregate, the sintering temperature should be determined individually depending on the raw materials used, using available techniques, e.g. high-temperature microscopy (HSM). The sintering method also enables the production of aggregate in a short time. However, sintering requires a large amount of energy during production, which affects its price. Generally, the sintering method is widely used around the world in some popular commercial products such as LECA and Lytag. These are some of the most popular artificial lightweight aggregates that have been commercialized on the market to replace natural aggregate. Due to costs, energy consumption and CO 2 emissions, new methods such as cold bonding and autoclaving are being investigated. In the autoclaving method, the hardening and strength of the granules are achieved by pressure and temperature. There are research papers describing the autoclaving process for the production of aggregates (Wang 2022, Wang 2020). In their research, the authors dry the aggregate at room temperature for 24 hours and then harden it at a temperature of up to 200° C for several hours. Through this procedure, they obtained aggregate very quickly. Tests have shown that a small amount of binding material is required to consolidate the aggregate. Unfortunately, there is not enough research on the effectiveness of the autoclaving method. This is because this method requires a specialized machine with precise temperature and pressure control to harden the aggregate. Furthermore, the autoclave is very expensive and requires high energy consumption and large production facilities to complete the process. The third popular bonding method is cold bonding. It is a process of strengthening larger particles obtained using pressure or pressureless agglomeration methods. In the cold setting process, cement or an alkaline activator is usually used as a binder. (Vali 2020 , Zafar 2021). The authors indicate that the cold bonding method was considered profitable because consolidation takes place at room temperature. Compared to other production processes, the cold bonding method minimizes energy consumption. In the case of cold gluing, the granules are dried at room temperature for at least 24 hours. Then, such granules require hardening, preferably in a closed chamber with steam, until the required strength is achieved (Abbas 2018, Rehman 2019, Wang 2022). The main challenge with cold set aggregates is the requirement for longer production times, as curing is typically required for 28 days. It is not always reasonable or possible to use cements or other alkaline activators. In the presented research works, the authors used a combined (hybrid) method - sintering and hydration hardening. Regardless of the uses of artificial aggregates in concrete production, LWA is worth investigating in particular to minimize environmental problems, along with maintaining long-term sustainability through improving water quality (filtration) (White 2009 ) or as a substrate for green roofs to mitigate the urban heat island effect ( Liu 2016 Kazemi M 2023). As a sustainable ecosystem system, the green roof is known for its ability to provide thermal resilience and buffer surface runoff of stormwater in urban areas. The shape and type of materials used in the drainage of the green roof and the substrate layer significantly affect the energy efficiency and water drainage (Ouldboukhitine 2015 , Vijayaraghavan 2016 , Farias 2017, Szota 2017, Stovin 2013). Due to the larger number of internal contact pores in the lightweight aggregate, moisture absorption is faster than with regular aggregate. Ecological issues, such as the limitation of natural resources and huge amounts of waste, are increasingly leading the developing civilization towards sustainable construction. The two main environmental problems are the depletion of natural resources and the disposal of waste generated during various processes. Therefore, the authors attempted to produce a new lightweight aggregate from by-products and waste materials. 2. Materials and methods 2.1 Characteristics of the raw materials used 2.1.1 Concrete recycled dust Construction waste from construction sites of new buildings, demolitions, modernization of existing buildings or from road infrastructure constitutes approximately 32% of the total mass of waste in the world. Among them, the largest share is construction rubble: concrete and brick (Ibrahim 2023). Concrete dust (0-2mm), generated during the production of coarse aggregates, is also produced from recycling elements from large slab blocks. These are prefabricated elements of various shapes and dimensions made of reinforced concrete elements that make up the structure of the block walls. They were widely used during communism in Poland and the GDR because they had a short construction time, but their durability was not ensured at a high level, which is why today there are a large number of prefabricated elements from demolitions or demolitions. The current situation in Ukraine also causes the formation of large amounts of large slab debris. Figure 1 shows the diffractogram of concrete dust used in the tests. The main crystalline phases are silica SiO 2 in the amount of 70.3%wt., calcium carbonate CaCO 3 in the amount of 8.7%wt (calcite, watertite) and aluminosilicates of sodium Na[AlSi 3 O 8 ] (albite) 11.2%wt and potassium K[AlSi 3 O 8 ] (microcline) 9.7%wt. 2.1.2 Waste clay from the Bełchatów open pit mine Coal clay from Bełchatów was used for plasticization and as a binder. Plasticization is the ability to create a mass using at least two products (water-sensitive, i.e. plastic raw material, e.g. clay, and water), which can be shaped in a selected way when wet, and retains its form after drying. Drying causes a loss of plasticity, but it is regained upon repeated contact with water; to obtain a permanent loss of plasticity, a firing process is used. Laboratory tests of the composition and physicochemical properties of samples of overburden rocks in deposits, i.e. boulder clays, silts and clays, in terms of their potential use, have been carried out at the Bełchatów Mine for many years, and the best of them are selectively extracted to mineral dumps. Rocks rich in smectites, which include the tested clays, could be useful for various applications. However, no work has been undertaken so far on using them for lightweight aggregates. The current resources in the deposit can be extracted in large, even industrial quantities. The average chemical composition of clay samples is given in Table 1 . They are characterized by a relatively high Al 2 O 3 content of 24.06% by weight for clay rocks. The presence of Fe 2 O 3 3.87% wt. is quite clearly visible. In turn, the following can be considered low: the amounts of alkalis Na 2 O and K 2 O in total do not exceed 1% by weight, the CaO content is 1.55% wt. and organic parts 0.5%wt. There are also traces of sulphur content (given in the oxide form) − 0.1% wt. The total loss on ignition was estimated at 4.46%wt and the average moisture was 8.92%wt. Table 1 Oxide chemical composition of the clay used to produce the aggregate Element %wt SiO 2 Al 2 O 3 Fe 2 O 3 TiO 2 CaO MgO MnO 63,67 24,06 3,87 0,43 1,55 1,1 0,02 K 2 O Na 2 O SO 3 P 2 O 5 Water LOI Organic 0,4 0,08 0,1 0,05 8,92 4,46 0,5 2.1.3 Residues from processing PET bottles Finding a use and then reusing PET bottles is a very good ecological step, because this product is used on a huge scale all over the world as packaging for various types of drinks and water. Due to their properties, PET packaging decomposes slowly, taking up to several hundred years, so it is important to reuse them. However, over time, through repeated use of the same waste, the material loses its properties and continuous production of bottles is impossible. Therefore, it is important to constantly look for opportunities where each type of waste could be successfully used. The material used in the research is final waste from the recycling process containing PET dust, label remnants (paper, foil) and other post-process residues. Table 2 shows the chemical composition of PET waste used in the research, obtained using the XRF method. The main ingredients identified were silicon, calcium and iron oxides. No oxides of harmful and toxic elements such as mercury, cadmium or lead were detected. However, this method has limitations in the identification of light elements such as H, O, C. It is these elements that polyethylene terephthalate C 10 H 8 O 4 consists of. The average ash content was determined to be 15.91%wt the remaining compounds burn out. Table 2 Oxide composition of PET waste after calcination Element %wt MgO Al 2 O 3 SiO 2 P 2 O 5 SO 3 Na 2 O K 2 O 2,73 5,79 32,92 0,76 0,70 0,34 1,44 CaO TiO 2 MnO Fe 2 O 3 CuO ZnO SrO 45,77 1,17 0,49 6,61 0,32 0,60 0,23 The calorific value of the waste was also tested - this is to improve the efficiency of sintering. The heat of combustion in the dry state Qs amounted to 29590 kJ/kg on average, and the emission of chlorine to the atmosphere was 0.80%wt. The calorific value of waste, PET, generates an exothermic reaction through combustion, which reduces energy consumption in the sintering process. This contributes to savings in the energy demand of the furnace, which results in lower gas emissions into the environment and, therefore, economic savings. The total moisture of the waste was 15.6% by weight. The analysis of the phase composition of the tested waste was very difficult. Only three phases that may be included in the tested material were identified. These are calcite, silica and dolomite (Fig. 2 ). The authors decided to provide the quantitative composition of the identified minerals, but it should be taken into account that this is an estimated analysis. Since the ultimate method of aggregate consolidation is sintering, tests using high-temperature microscopy (HSM) were carried out to illustrate changes in the sample geometry. Figure 3 shows the research results. In the case of testing PET waste, no temperatures characteristic of sintered materials were observed in the sample. A geometric change called "corner rounding" was recorded at 845°C (5% change in sample dimensions) (a). Then the material shrinks and decomposes more and more without sintering. From a temperature of 1160°C, a rapid change in the dimensions of the sample is observed (b,c). At a temperature of 1200°C, only loose ash remains (d), consisting mainly of silica and calcium oxide. 2.2 Manufacturing method – granulation The production process of artificial aggregate consists of five stages: grinding of raw materials, usually combined with drying or separate drying of wet raw materials, mixing of raw materials, granulation, classification and hardening. In the first stage, drum and drying ball mills are usually used, in which coarse-grained raw materials are ground. Raw materials can be ground separately or together in appropriate proportions, thanks to which the mixing process takes place. In the second stage, appropriately selected ingredients are mixed until the mixture reaches optimal homogenization, at this stage a binder may also be added if necessary. In the third stage, the mixture of raw materials is subjected to the granulation process by agglomeration of small particles using water and an appropriate binder, if the process requires it. Depending on the appropriately selected operating parameters of the granulator and the moisture content (water dosage), the appropriate size of granules will be produced in the device. In the fourth stage, depending on the type of machines used, granules may be classified according to grain size, and fine-grained products and cracked granules are returned to the granulation process. The hardening of fresh granules in the fifth stage is achieved by drying. The flowchart of lightweight aggregate production can be illustrated in Fig. 4 . The consolidation process, called structured agglomeration of powders with a high degree of dispersion, aims to combine small dust particles to create larger aggregates (over 1 mm in size) with appropriate properties. This process is used to obtain a form of product that will be convenient for use by recipients or possible for further use in appropriate technologies. Dynamic granulation, takes place in dynamic counter-rotating granulators with variable rotation speed of the drum and mixer with opposite directions of rotation (Fig. 5 a). The machine enables the processing of various types of consistency into selected forms of granules. Mixing and granulation takes place in one device and ensures the highest standards in terms of product quality, energy consumption and efficiency per volume unit of the technological device. The raw materials become cohesive in a very short time - several dozen seconds, and because it is a closed chamber system, dust formation is limited to a minimum. Drum granulation - the process is characterized by continuity thanks to the movement of the granulated material inside an open drum inclined at a small angle (Fig. 5 b). Two methods of producing granules were used in the research. Using a dynamic counter-rotating granulator and a drum granulator. In the first case, the granules were smaller (on average 5 mm in diameter, Fig. 6 a) and the process occurred much faster, within a few minutes. However, in the second one, a smaller number of balls with a coarser fraction was obtained (approximately 10 mm on average, Fig. 6 b). The produced granulates were hardened using a combined method - sintering and hydration. 2.3 Hardening process 2.3.1 Sintering Sintering is a basic technological process in the production of materials with a fixed shape. When heated to an appropriate temperature, lower than the melting point, the set of contacting grains bond together, forming a polycrystal. The essence of this process are mass transfer mechanisms that lead to macroscopic changes in the material. These include: reduction of porosity and the accompanying thickening and shrinkage of the sintered system, as well as an increase in its mechanical strength. The basic driving force of the sintering process is the energy of the free surfaces of the set of particles. The specific surface area, which is the total surface area of the particles of crushed material per unit mass, is directly proportional to the susceptibility to sintering. In other words, the finer the mineral fraction, the faster the shape preservation process. The tested materials are fine-grained, so the transport of matter will occur quickly and uniformly (Lis 2000 ). The samples were fired in an FCF 12SHM electric furnace from Czylok, operating temperature up to 1250 o C, working chamber with a capacity of 8 dm 3 2.3.2 Hydration The hydration process is a multi-stage process. However, it seems that from the point of view of using calcined concrete dust and PET ash as a grout ingredient, the most important thing is the hydration of tricalcium aluminate. This hydration is complicated, and the product of this reaction are hydrated calcium silicates insoluble in water (Kurdowski 2010 ). To ensure a fully developed hydration process, the samples were maintained in distilled water for 28 days. 3. Results and discussion 3.1 Formula selection In order to obtain the best product, three mixtures were created containing different amounts of aggregate ingredients, as shown in Table 3 . Table 3 Raw material compositions of the produced aggregates Sample acronym Granulation type Clay Concrete dust PET residues %wt I GD dynamic 40 30 30 II GD 42 42 16 III GD 32 56 12 I GB drum 40 30 30 II GB 42 42 16 III GB 32 56 12 3.2 Aggregate before sintering Generally, sintering is a three-step process: stage I – initial sintering phase – observed when the material temperature is approximately 0.25 of the melting temperature, no shrinkage is observed at this stage, the original arrangement of layers in the aluminosilicates remains intact, the products are dried with a gradual increase in temperature to 200°C. This process is characterized by the removal of the remaining free water, the content of which in the raw material is still several percent. stage II – intermediate phase – occurs when the material temperature is 0.25–0.75 of the melting point, at this stage the beginning of shrinkage is noticeable, grain growth and material thickening occur. During the second firing period, also called the dehydration period, which includes a further increase in temperature to approximately 600°C, chemically bound water is released. At the same time, the dehydration process decomposes organic substances and begins to decompose chemical compounds and minerals. stage III – final phase – end of the thickening phase, transformation of open pores into closed ones and their partial disappearance, with continuous grain growth. This stage, called the vitrification period, is characterized by significant changes in the mineralogical composition of the mass. In the granule sintering process, attempts were made to prevent stage III from fully developing in order not to close the high porosity of the material. The set temperature was intended to roast (chemically change) raw materials undergoing thermal dissociation. As a result, this was to increase the porosity of the aggregates due to escaping gases and burning of organic parts, which also contributes to a decrease in the apparent density and an increase in the absorbability of the aggregate. Changing these properties will have a positive effect, for example, on the water retention of aggregates. This optimally selected temperature ensures the formation of a durable sinter, and durability is achieved through the glassy phase that sticks the powder particles together. (Lis 2000 , Liu 2018,). The characteristic temperatures of the sinter were determined using a Misura® HSM high-temperature microscope. Cylindrical test samples (ø = 2 mm, h = 3 mm) were pressed manually. The heating rate of the samples was 10°C/min. Additionally, Fig. 7 shows an example image obtained from a high-temperature microscope. The measurement involves observing changes in the sample's contours as the temperature increases, which allows the determination of characteristic temperatures, such as: Sintering temperature Ts – temperature at which the sample reaches 99% of its initial height; Softening temperature Tm – also referred to as the beginning of melting, at which the sample shows a pronounced rounding of the edges; Hemisphere temperature Tp – the height of the sample is half the diameter, it determines the end of its melting; Spreading temperature Tr – the height of the sample is equal to 1/3 of the initial height (Boccaccini 1999 ). The results from the measurement of characteristic temperatures are presented in Table 4 and Fig. 8 . Samples with extreme clay contents were selected for testing, i.e. sample II with a clay content of 42 wt%, and sample III with a lower clay content of 32 wt%, because this raw material is responsible for obtaining the sinter (Table 3 ). The granulation process method had no effect on the sintering process. No significant differences were noticed in the sintering process. Table 4 Summary of characteristic temperature values [°C] Sample GDII, GBII GDIII, GBIII Sintering temperature T s 970 974 Softening temperature T m 1161 1158 Hemisphere temperature T p 1201 1198 Spreading temperature T r 1213 1215 Based on the obtained test results, it was decided to use firing at a temperature of 1000°C (slightly above the minimum sintering temperature). This temperature guarantees obtaining a durable sinter, and at the same time no significant shrinkage of the sample is observed and the porosity does not close. 3.3 Sintered aggregate The tested materials have a complex mineralogical composition, hence the sintering system is complicated. The appropriate amount of calcium carbonate in the mass causes the formation of CaO (decarbonation of CaCO 3 ), and consequently reduces the viscosity of the liquid phase formed at high temperatures and facilitates the sintering process. The second effect is the formation of pores as a result of decarbonation, which create a network of interconnected channels (open porosity increases). In raw materials with an excess of CaCO 3 , anorthite, calcium aluminates and silicates, and braunmilerite are formed at temperatures above 960°C (Fig. 9). The decarbonization reaction of calcite and dolomite proceeds intensively at normal pressure. The presence of dehydrated clay and inorganic admixtures Fe 2 O 3 , TiO 2 , SiO 2 and others contribute to the acceleration of the decarbonization reaction. The dehydration of clay minerals is primarily influenced by the firing environment. In addition, the presence of Fe 2+ in clays promotes the formation of new phases. The group of reactions in solid phases of clays that take place through the transport of matter can be described using the following formulas: 3(Al 2 O 3 ·2SiO 2 ) → 3(3Al 2 O 3 ·2SiO 2 ) + 4SiO 2 , (mullite, cristobalite) 4(Al 2 O 3 ·2SiO 2 ) + 3Fe 2 O 3 → 4(FeO·Al 2 O 3 ) + 4(2FeO·SiO 2 ) + 7SiO 2 + 1 1 / 2 O 2 , (hercynite, fayalite, cristobalite) 4(Al 2 O 3 ·2SiO 2 )+ 6 FeO → 4(FeO·Al 2 O 3 )+ 4(2FeO·SiO 2 ) + 7SiO 2 , (hercynite, fayalite, cristobalite) 3(Al 2 O 3 ·2SiO 2 ) + 3CaCO 3 + 4SiO 2 → 3(CaO·Al 2 O 3 2SiO 2 ) + 3CO 2 , (anortite) Cristobalite formed during firing of montmorillonite-kaolinite raw materials "loosens the body" and increases its permeability and water absorption. (Kunag 1997, Nov 2000, Kang 2005 , Kłosek 2013, Zawrah 2020). In order to determine temperature transformations and the mass loss of the tested samples, DSC analyzes were performed. The tests were performed on dried and powdered samples. The measurement results are presented in Fig. 9. When roasting clay minerals, structural changes occur, mainly involving the removal of hydroxyl groups from their structures (dehydroxylation) and, consequently, the formation of active forms. Mass loss is recorded in the temperature range 610–650°C and is caused by dehydroxylation of clay minerals. Dehydroxylation of clay minerals is a complex process that occurs in a wide range of temperatures, even up to 1200°C, where high-temperature swelling is observed. Since the second component was recycled concrete dust, thermal effects will also come from the decomposition of this material. The analyzed thermogram shows a blurred peak starting at a temperature of 250°C up to a temperature of 400°C. In the range of such temperatures, ettringite is completely dehydrated and the dehydration of the C-S-H phase begins. Dehydroxylation of portlandite also partially occurs. It turns into free lime, which allows it to re-bind when in contact with water. At a temperature of 600°C, most of the C-S-H phase decomposes. This makes roasting recycled fines at a temperature level of 650°C a favorable phenomenon. This is related to the binding properties of this fraction and the possibility of using it as a substitute for cement or an active additive to the composite. Weight loss is also observed around 900–1000°C, so it can be concluded that the samples decompose carbonates and the remains of clay minerals 3.3.1 Leaching of soluble compounds and secondary hydration Samples of fired aggregate with cement dust were subjected to an additional hydration process. The hydration mechanism of calcium aluminates consists of the dissolution process, where the anhydrous phases of clay cement dissolve and then precipitate from the solution in the form of hydrates (chemical compounds from the CaO·Al 2 O 3 ·H 2 O system). There are three main phases of the hydration process: dissolving, nucleation, precipitation. The hydration process is initiated by hydroxylation of the cement surface. In the next stage, the cement dissolves in water and releases calcium and aluminum ions into the solution. When the ion concentration exceeds the hydrate solubility level, a small amount of hydrate gel is formed. Dissolution continues with a simultaneous increase in the concentration of calcium and aluminum ions in the water until the saturation level is reached. Crystal nuclei are then formed in large numbers - the nucleation phase. Hydrates begin to precipitate en masse, which leads to a decrease in ion concentration. This is a dynamic process that leads to the dissolution of the rest of the anhydrous cement. In the physical sense, we are dealing with the growth of hydrated crystals that interlock and bond with each other, resulting in the formation of a monolith on a macro scale. The driving force is the lower solubility of hydrates in water than that of anhydrous calcium aluminate. Hydration is a process involving the transfer of ions into solution. This can be confirmed using conductometric measurements. For this purpose, a cement sample is placed in water and tested for ionic conductivity. Its value increases as the number of ions per unit volume increases. For this purpose, tests of the concentrations of substances soluble in water were carried out by performing electrolytic conductivity tests. Additionally, pH changes were monitored. For this purpose, fired aggregate with an appropriate weight of approximately 10 g was immersed in 100 ml of distilled water (Fig. 10 ). Table 5 shows the measurement results. The parameters of distilled water used for testing were pH 6.04 and conductivity 4.25 µS. Changes in aggregate mass were also recorded after 14 and 28 days, thus checking the condition of the sinter and its resistance to water. Table 5 Results of measurements of changes in pH and conductivity of solutions Time Parameter I GD II GD III GD I GB II GB III GB Day 1 pH [-] 11,00 11,21 11,78 11,03 11,59 11,67 Day 2 10,40 11,00 11,80 10,40 11,67 11,40 Day 3 9,80 10,49 11,16 10,35 11,40 11,41 Day 7 9,87 10,41 10,98 10,00 10,91 11,03 Day 14 9,65 10,30 10,36 9,16 9,64 9,72 Day 28 9, 34 9,87 9,90 9,16 9,56 9,60 Day 1 Conductivity [µS] 107 175 250 189 184 232 Day 2 464 482 544 442 431 525 Day 3 691 723 757 703 699 742 Day 7 456 480 452 432 460 566 Day 14 250 275 237 189 184 192 Day 28 258 265 243 201 164 132 Day 1 Dry weight [g] 10,6567 10,0892 10,7055 10,0908 10,3104 10,4344 Saturated weight [g] 14,8484 15,5041 15,7730 15,5412 15,1895 14,4545 Day 14 15,1304 15,6010 16,1869 15,5705 15,2077 15,0797 Day 28 15,2081 15,6103 16,4311 15,6730 15,2927 15,3022 There are three stages that can occur in an ionic conductivity test: Rapid increase in conductivity, associated with a sharp increase in the amount of Ca 2+ and [Al(OH) 4 ] − ions. During this process, the slow deposition of primary hydrates in the form of a gel is visible. Saturation state - where crystal nuclei are formed Crystallization of hydration products (Kurdowski 2010 ) The test results confirm the ongoing hydration process. After mixing the aggregate with water, the liquid phase is rapidly saturated with calcium ions, and the pH of the solution increases rapidly. On the first day of measurement, the highest pH values are observed in the case of aggregates with the highest amount of cement (III GD and III GB; pH above 11. The high pH persists for at least two weeks and in the following days it begins to slowly decrease, but does not reach neutral values. At the same time, with changes in pH, changes in the conductivity of the solution are observed. In the dissolution phase, it is the highest (reaching values above 750 µS in the case of aggregate samples with the highest cement content (Fig. 11 ). About 24 hours after the start of the measurements, the conductivity begins to decrease because crystallizing phases begin to precipitate aluminate, while K+, Na + and OH- ions remain in the solution. Hence the persistently high pH. Crystallization of cement hydration products causes an increase in the mass of the granules (Table 6 ). The hydration process also causes additional hardening of the aggregate. After 28 days, a second test was carried out in water, and pH and conductivity were similarly measured. For this purpose, aggregate samples were filtered and poured with fresh distilled water with a pH of 6.17 and a conductivity of 6.13 µS. Table 6 shows the measurement results. The pH indicator is neutral throughout the entire research period, and no increased salt leachability was observed. Table 6 Measurements of changes in pH and conductivity of solutions - second measurement series Time Parameter I GD II GD III GD I GB II GB III GB Day 1 pH [-] 7,23 7,12 7,54 7,29 7,70 7,56 Day 2 7,17 7,28 7,49 7,26 7,48 7,79 Day 7 7,27 7,18 7,31 7,16 7,32 7,61 Day 14 7,02 7,20 7,34 7,08 7,34 7,50 Day 1 Conductivity [µS] 234 219 261 214 221 241 Day 2 297 278 290 271 256 289 Day 7 279 281 250 250 242 249 Day 14 283 275 267 229 256 271 3.3.2 Bulk and apparent density All obtained granulates had an apparent density below 2g/cm 3 , which meets the standards for classifying the aggregate as light. Slightly lower bulk densities were observed in materials obtained using the drum method - this is due to the coarser and less differentiated aggregate fraction. The lowest densities were obtained in samples of composition III containing 52% of concrete dust, however, these values may change due to the ongoing hydration process. It should be noted, however, that the deviations are small and may be negligible on a larger scale. Table 7 shows the measurement results. Table 7 Average apparent and bulk densities of the tested samples Parameter I GD II GD III GD I GB II GB III GB Bulk desity [g/cm 3 ] 0,79 0,80 0,76 0,65 0,70 0,68 Apparent density [g/cm 3 ] 1,43 1,43 1,31 1,39 1,35 1,23 3.3.3 Kinetics of water release The obtained aggregates are very porous, it is open porosity. Figure 12 shows the dynamics of water absorption. Since the aggregates are intended for use on green roofs, tests were carried out using a precise moisture analyzer with a drying chamber (Fig. 13 ), which ensures a uniform drying temperature during measurement. Measurements were carried out at a temperature of 100°C, the average initial weight of the samples was 1.5 g. Tables 8 and 9 present the measurement results. Table 8 Recorded water discharge data Time, [min] I GB II GB III GB I GD II GD III GD Loss of weight [%wt] 5 4,3 4,2 4,8 9,88 10,17 10,9 10 11,25 9,2 11,6 19,76 22,12 21,99 15 19,21 15,59 18,35 26,99 27,11 28,76 20 25,95 20,92 24,9 31,79 30,28 33,59 25 29,78 25,85 31,08 34,29 38,07 43,24 30 32,84 29,39 34,91 - - - Table 9 Total weight loss depending on time I GB II GB III GB I GD II GD III GD całkowity ubytek masy [%wt] 32,86 33,83 35,89 34,45 39,02 45,62 czas końcowy 30min 41s 35min 18s 34min 4 s 25min23 25min 31s 23 min 59s It turns out that the granulation method affects the rate of water release - granules produced with a drum granulator release water much longer (Table 8 ), on average the difference is 8 minutes. This is influenced by both the aggregate fraction and the type and size of porosity. Materials with open porosity will behave differently from those with partially closed porosity. The more open pores, the greater possible water retention. The composition of the samples also influenced the drying dynamics. Interestingly, samples with composition I absorbed the least amount of water, which is justified because they contained the largest amount of clay, which partially forms a glassy phase during sintering, closing the pores. 3.3.3 SEM scanning microscopy, Microstructure tests of selected aggregates were carried out. Samples of composition II produced by both granulation methods, i.e. drum and dynamic, were selected for testing. The surface and interior of the samples were examined. EDS tests of the materials were also performed. Microscopic photos are shown in Figs. 14 – 17 . Porosity is higher in aggregate formed using the dynamic granulation method, the structure is more porous, the grains are less stuck together, this is especially visible at lower magnifications of 50 times - Figs. 16 and 17 . The aim of the research was to produce a material with high porosity that can absorb large amounts of water. Both granulation methods generally meet these assumptions, however, the microstructure of the GD granules seems to be more favorable. The GB II sample was selected for testing its chemical composition using EDS energy dispersive spectroscopy - there is no need to test the material made with the second method because the material components and their quantity are the same. Elemental analysis at various points shows that the chemical composition of aggregates is diverse, there are places where there is mainly silica up to 94 wt%, but there are also micro-areas with very different contents of the main oxides, i.e. SiO 2 − 44 wt%, CaO − 22 wt% Al 2 O3–17%tue An example analysis is shown in Fig. 18 . Conclusions The problem of disposal and management of solid waste materials has become one of the main environmental, economic and social problems. The use of solid waste in the production of lightweight aggregate not only solves the problem of waste disposal, but also helps in transforming waste into useful and profitable products. Recycling PET waste into lightweight aggregates seems to be a feasible solution, not only to the problem of disposal of this type of waste, but also an economical option for the production of lightweight aggregates. Concrete dust from demolition of difficult use is used in this technology as a material that limits plasticity, but also supports hardening through secondary hydration. The aim of the research was to produce a light aggregate from by-products and waste materials, this goal was achieved, a light and highly porous aggregate was obtained that can be used in various industries, including sustainable architecture (including green roofs). In further research, the authors will use other plastic raw materials, e.g. clays produced during the washing and processing of gravel, which are so far treated as waste material and stored in water reservoirs. Declarations Author Contributions : AS - contributed to conceptualization, methodology, validation, formal analysis, investigation, data curation, writing—original draft, and visualization. TG - contributed to methodology, validation, formal analysis, investigation, data curation, resources, writing—review and editing, and supervision, Funding :. Research project partly supported by program „Excellence initiative – research university Institutional Review Board Statement : Not applicable. Informed Consent Statement : Not applicable. Conflicts of Interest : The authors declare no conflicts of interest. 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Cite Share Download PDF Status: Published Journal Publication published 23 Jul, 2024 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 18 Jun, 2024 Reviews received at journal 13 Jun, 2024 Reviewers agreed at journal 22 May, 2024 Reviews received at journal 24 Apr, 2024 Reviewers agreed at journal 21 Apr, 2024 Reviewers agreed at journal 19 Apr, 2024 Reviewers agreed at journal 19 Apr, 2024 Reviewers invited by journal 19 Apr, 2024 Editor assigned by journal 19 Apr, 2024 Editor invited by journal 10 Apr, 2024 Submission checks completed at journal 10 Apr, 2024 First submitted to journal 03 Apr, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4214334","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":291083132,"identity":"6d41855c-8282-42a0-a6a4-75607f03fbac","order_by":0,"name":"Agata 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18:00:29","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":121834,"visible":true,"origin":"","legend":"\u003cp\u003eX-ray of PET waste with estimated quantitative analysis\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-4214334/v1/92c7096e6704bb049db0cddb.png"},{"id":54929803,"identity":"32ca8908-db5b-4e6b-818d-f6b45f1361a1","added_by":"auto","created_at":"2024-04-18 18:00:29","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":91453,"visible":true,"origin":"","legend":"\u003cp\u003eImages of PET waste obtained from a high-temperature microscope, initial stage - 5% change in dimensions (a), beginning of a rapid geometric change (b), combustion of the PET material (c) loose ash 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images from a high-temperature microscope for a sample with the method of determining characteristic temperatures\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-4214334/v1/69a8b2139c37a0e91ad6451a.png"},{"id":54929810,"identity":"6b8453ce-377d-4118-9128-511c122c301f","added_by":"auto","created_at":"2024-04-18 18:00:29","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":31590,"visible":true,"origin":"","legend":"\u003cp\u003eAverage sintering diagram of aggregate, the minimum sintering temperature is marked with a red line.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-4214334/v1/42d324d9e2d1ec4dd1963558.png"},{"id":54929807,"identity":"76826840-c643-44cf-9493-d4a7aa6bb292","added_by":"auto","created_at":"2024-04-18 18:00:29","extension":"jpeg","order_by":9,"title":"Figure 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11","display":"","copyAsset":false,"role":"figure","size":110205,"visible":true,"origin":"","legend":"\u003cp\u003eVariability of conductivity and pH and mass increase over time\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-4214334/v1/600efa78ac9b4de6856c285b.png"},{"id":54929817,"identity":"8413e2ca-3329-4b0d-864a-f14c0b6e0278","added_by":"auto","created_at":"2024-04-18 18:00:30","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":827884,"visible":true,"origin":"","legend":"\u003cp\u003eAir escaping from the aggregate granules\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-4214334/v1/1a0ab35622594c17c5cf0ecf.png"},{"id":54929808,"identity":"bba1950a-521e-4aeb-a3a0-23c2b9ae84a8","added_by":"auto","created_at":"2024-04-18 18:00:29","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":2120116,"visible":true,"origin":"","legend":"\u003cp\u003eMeasurement of drying speed, preparation of granules for testing (a) beginning of drying (b) recorded weight loss after drying (c)\u003c/p\u003e","description":"","filename":"13.png","url":"https://assets-eu.researchsquare.com/files/rs-4214334/v1/484ee724a9f26c02253ad505.png"},{"id":54929818,"identity":"a70ec3f7-8019-4188-b2df-9171d8832cbd","added_by":"auto","created_at":"2024-04-18 18:00:30","extension":"jpg","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":416062,"visible":true,"origin":"","legend":"\u003cp\u003eMicrophotograph of the sample GB II surface - magnification 50x and 2000x, respectively\u003c/p\u003e","description":"","filename":"14.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4214334/v1/173c31c636afd42a2f65387a.jpg"},{"id":54929819,"identity":"cafaccbb-716b-4957-ab05-79ff092a7736","added_by":"auto","created_at":"2024-04-18 18:00:31","extension":"jpg","order_by":15,"title":"Figure 15","display":"","copyAsset":false,"role":"figure","size":519124,"visible":true,"origin":"","legend":"\u003cp\u003eMicrophotograph of the GB II sample fracture - magnification 50x and 2000x, respectively\u003c/p\u003e","description":"","filename":"15.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4214334/v1/54ad81f04a84d2c299ec898b.jpg"},{"id":54930267,"identity":"66e28a2d-4ca3-4604-a033-9d9eb611337b","added_by":"auto","created_at":"2024-04-18 18:08:29","extension":"jpg","order_by":16,"title":"Figure 16","display":"","copyAsset":false,"role":"figure","size":386222,"visible":true,"origin":"","legend":"\u003cp\u003eMicrophotograph of the GD II sample surface - magnification 50x and 2000x, respectively\u003c/p\u003e","description":"","filename":"16.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4214334/v1/399885335f0543e0eca7863e.jpg"},{"id":54930268,"identity":"f2dfaf1c-771b-4abb-b8d5-5583532ae8e0","added_by":"auto","created_at":"2024-04-18 18:08:29","extension":"jpg","order_by":17,"title":"Figure 17","display":"","copyAsset":false,"role":"figure","size":441408,"visible":true,"origin":"","legend":"\u003cp\u003eMicrophotograph of the GD II sample fracture - magnification 50x and 2000x, respectively\u003c/p\u003e","description":"","filename":"17.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4214334/v1/f7ffb2081ef95abec3ee1d15.jpg"},{"id":54929814,"identity":"abe47e42-1449-4641-afa0-1c8f095213e4","added_by":"auto","created_at":"2024-04-18 18:00:30","extension":"png","order_by":18,"title":"Figure 18","display":"","copyAsset":false,"role":"figure","size":1468216,"visible":true,"origin":"","legend":"\u003cp\u003eMicrophotograph with marked EDS analysis points and the results of this analysis\u003c/p\u003e","description":"","filename":"18.png","url":"https://assets-eu.researchsquare.com/files/rs-4214334/v1/634b13d07b798a7399ef0a51.png"},{"id":61596186,"identity":"04276f7e-e181-4806-abe4-6ab64e3a92b7","added_by":"auto","created_at":"2024-08-01 17:25:33","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":13535023,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4214334/v1/4c7e42b8-1d00-47ff-81a6-d4e10ddc849e.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Artificial lightweight aggregate made from alternative and waste raw materials, hardened using the hybrid method","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eLightweight aggregate (LWA) is defined as solid substance with an apparent density of less than 2.0 g/cm\u003csup\u003e3\u003c/sup\u003e and a bulk density of less than 1.2 g/cm\u003csup\u003e3\u003c/sup\u003e (EN 13055:2016). LWAs are porous and often granular materials that are widely used in architecture, landscaping and geotechnics. The porosity of these materials can be either open or closed, which affects their applicability. For example, aggregates with open porosity can provide effective drainage but also micro water retention. Furthermore, they can provide better sound absorption and thermal insulation. Lightweight aggregates can be divided into the following categories (Kumar 2010, Franus 2015, Alqahtani \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e):\u003c/p\u003e\n\u003col\u003e\n\u003cli\u003e\n\u003cp\u003enaturally occurring raw materials that require further processing, such as clays and intrusive shales and vermiculite;\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003enaturally occurring raw materials that do not require processing, such as pumice stone, foamed lava, volcanic tuff and porous limestone.\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eindustrial wastes such as sintered fly ash or foamed blast furnace slag.\u003c/p\u003e\n\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eThe most commonly used artificial aggregate in many industries is sintered fly ash. The use of lightweight aggregate in concrete has gained popularity due to its low density, good thermal conductivity and strength, environmental friendliness and many other advantages. (George \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e, Sun 2021).\u003c/p\u003e\n\u003cp\u003eA global environmental problem due to the use of large amounts of natural resources is generated by the construction industry. Most of the aggregates used in this industry are obtained from natural resources. There is a continuous increase in the production of construction materials and therefore non-renewable natural resources are diminishing at an accelerating rate due to the high demand for their use in concrete production. Of course, for heavy-duty, high-strength and cover concretes, the use of quality natural aggregates appears to be essential. However, modern construction is moving away from oversized heavy structures. The development of the manufacture of artificial of lightweight materials such as lightweight aggregate will help minimize the use of natural resources. Lightweight aggregate is significantly different from conventional aggregate. The obtained modifications may bring benefits and new challenges for designers for many reasons, for example weight reduction, improved acoustic or thermal properties, drainage or filtration capabilities. (Kumar 2010, Alqahtani \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e, Hao 2022).\u003c/p\u003e\n\u003cp\u003eUndoubtedly, the consumption of construction aggregates depletes natural resources and poses a direct threat to the environment. Due to the increasing expansion of construction, resources of natural aggregates are rapidly decreasing. There is a local shortage of resources that requires proper use for sustainable development (Kozioł 2016. Khan 2023). Bibliographic research conducted by the authors shows that the dominant issue in the field of waste and recycled materials is the technology of building materials, and in particular the technology of concrete. It can be said that these issues are present in virtually every scientific and economic field. Starting from mineral and biotic resources, through broadly understood chemical and physical sciences, to geotechnics (Stempkowska 2023). An interesting direction of use of waste materials are fired materials such as bricks, tiles, lightweight aggregates (Danish 2022, Izak 2023,, Simao 2023, Singh 2023).\u003c/p\u003e\n\u003cp\u003eHowever, the authors of the above publications point out the difficulties in using waste materials. Despite homogenization processes, mineral waste is characterized by low composition stability and the presence of soluble compounds. Such compounds may cause efflorescence on the surface or increased leachability of harmful substances, which causes functional defects. Natural sand can be replaced using by-products from coarse aggregate production, which are widely available, cheaper and reduce the extraction of natural sand (Altuki 2022). Additionally, manufactured sand has become a popular choice to replace natural sands because it is often extracted from streambeds and sand extraction is considered environmentally harmful (Franus 2015). In addition, the produced sand, which is made from hard igneous, sedimentary or metamorphic rocks, can be produced locally, reducing transportation costs.\u003c/p\u003e\n\u003cp\u003eThe demand for aggregates with a coarser fraction is different. Such materials, obtained from waste raw materials, must be integrated. They can be obtained in several ways, such as:\u003c/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003ecold consolidation\u0026thinsp;~\u0026thinsp;25\u0026deg;C (cold setting, cementation, geopolymerization) (Rehman 2019, Zafar 2021)\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eautoclaving to about 200\u0026deg;C\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003esintering, at temperatures above 900\u0026deg;C (Hao 2022).\u003c/p\u003e\n\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eGenerally, lightweight aggregate produced at, for example, ~\u0026thinsp;1200\u0026deg;C provides the best mechanical properties, but deteriorates its porosity. To obtain the most favorable properties of artificial aggregate, the sintering temperature should be determined individually depending on the raw materials used, using available techniques, e.g. high-temperature microscopy (HSM). The sintering method also enables the production of aggregate in a short time. However, sintering requires a large amount of energy during production, which affects its price. Generally, the sintering method is widely used around the world in some popular commercial products such as LECA and Lytag. These are some of the most popular artificial lightweight aggregates that have been commercialized on the market to replace natural aggregate. Due to costs, energy consumption and CO\u003csub\u003e2\u003c/sub\u003e emissions, new methods such as cold bonding and autoclaving are being investigated.\u003c/p\u003e\n\u003cp\u003eIn the autoclaving method, the hardening and strength of the granules are achieved by pressure and temperature. There are research papers describing the autoclaving process for the production of aggregates (Wang 2022, Wang 2020). In their research, the authors dry the aggregate at room temperature for 24 hours and then harden it at a temperature of up to 200\u0026deg; C for several hours. Through this procedure, they obtained aggregate very quickly. Tests have shown that a small amount of binding material is required to consolidate the aggregate. Unfortunately, there is not enough research on the effectiveness of the autoclaving method. This is because this method requires a specialized machine with precise temperature and pressure control to harden the aggregate. Furthermore, the autoclave is very expensive and requires high energy consumption and large production facilities to complete the process.\u003c/p\u003e\n\u003cp\u003eThe third popular bonding method is cold bonding. It is a process of strengthening larger particles obtained using pressure or pressureless agglomeration methods. In the cold setting process, cement or an alkaline activator is usually used as a binder. (Vali \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e, Zafar 2021). The authors indicate that the cold bonding method was considered profitable because consolidation takes place at room temperature. Compared to other production processes, the cold bonding method minimizes energy consumption. In the case of cold gluing, the granules are dried at room temperature for at least 24 hours. Then, such granules require hardening, preferably in a closed chamber with steam, until the required strength is achieved (Abbas 2018, Rehman 2019, Wang 2022). The main challenge with cold set aggregates is the requirement for longer production times, as curing is typically required for 28 days. It is not always reasonable or possible to use cements or other alkaline activators.\u003c/p\u003e\n\u003cp\u003e\u003cspan class=\"Underline\"\u003eIn the presented research works, the authors used a combined (hybrid) method - sintering and hydration hardening.\u003c/span\u003e\u003c/p\u003e\n\u003cp\u003eRegardless of the uses of artificial aggregates in concrete production, LWA is worth investigating in particular to minimize environmental problems, along with maintaining long-term sustainability through improving water quality (filtration) (White \u003cspan class=\"CitationRef\"\u003e2009\u003c/span\u003e) or as a substrate for green roofs to mitigate the urban heat island effect ( Liu \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e Kazemi M 2023). As a sustainable ecosystem system, the green roof is known for its ability to provide thermal resilience and buffer surface runoff of stormwater in urban areas. The shape and type of materials used in the drainage of the green roof and the substrate layer significantly affect the energy efficiency and water drainage (Ouldboukhitine \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e, Vijayaraghavan \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e, Farias 2017, Szota 2017, Stovin 2013). Due to the larger number of internal contact pores in the lightweight aggregate, moisture absorption is faster than with regular aggregate.\u003c/p\u003e\n\u003cp\u003eEcological issues, such as the limitation of natural resources and huge amounts of waste, are increasingly leading the developing civilization towards sustainable construction. The two main environmental problems are the depletion of natural resources and the disposal of waste generated during various processes. Therefore, the authors attempted to produce a new lightweight aggregate from by-products and waste materials.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n\u003ch2\u003e2.1 Characteristics of the raw materials used\u003c/h2\u003e\n\u003cdiv id=\"Sec4\" class=\"Section3\"\u003e\n\u003ch2\u003e2.1.1 Concrete recycled dust\u003c/h2\u003e\n\u003cp\u003eConstruction waste from construction sites of new buildings, demolitions, modernization of existing buildings or from road infrastructure constitutes approximately 32% of the total mass of waste in the world. Among them, the largest share is construction rubble: concrete and brick (Ibrahim 2023). Concrete dust (0-2mm), generated during the production of coarse aggregates, is also produced from recycling elements from large slab blocks. These are prefabricated elements of various shapes and dimensions made of reinforced concrete elements that make up the structure of the block walls. They were widely used during communism in Poland and the GDR because they had a short construction time, but their durability was not ensured at a high level, which is why today there are a large number of prefabricated elements from demolitions or demolitions. The current situation in Ukraine also causes the formation of large amounts of large slab debris. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e shows the diffractogram of concrete dust used in the tests. The main crystalline phases are silica SiO\u003csub\u003e2\u003c/sub\u003e in the amount of 70.3%wt., calcium carbonate CaCO\u003csub\u003e3\u003c/sub\u003e in the amount of 8.7%wt (calcite, watertite) and aluminosilicates of sodium Na[AlSi\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e8\u003c/sub\u003e] (albite) 11.2%wt and potassium K[AlSi\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e8\u003c/sub\u003e] (microcline) 9.7%wt.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section3\"\u003e\n\u003ch2\u003e2.1.2 Waste clay from the Bełchat\u0026oacute;w open pit mine\u003c/h2\u003e\n\u003cp\u003eCoal clay from Bełchat\u0026oacute;w was used for plasticization and as a binder. Plasticization is the ability to create a mass using at least two products (water-sensitive, i.e. plastic raw material, e.g. clay, and water), which can be shaped in a selected way when wet, and retains its form after drying. Drying causes a loss of plasticity, but it is regained upon repeated contact with water; to obtain a permanent loss of plasticity, a firing process is used. Laboratory tests of the composition and physicochemical properties of samples of overburden rocks in deposits, i.e. boulder clays, silts and clays, in terms of their potential use, have been carried out at the Bełchat\u0026oacute;w Mine for many years, and the best of them are selectively extracted to mineral dumps. Rocks rich in smectites, which include the tested clays, could be useful for various applications. However, no work has been undertaken so far on using them for lightweight aggregates. The current resources in the deposit can be extracted in large, even industrial quantities. The average chemical composition of clay samples is given in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. They are characterized by a relatively high Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e content of 24.06% by weight for clay rocks. The presence of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e 3.87% wt. is quite clearly visible. In turn, the following can be considered low: the amounts of alkalis Na\u003csub\u003e2\u003c/sub\u003eO and K\u003csub\u003e2\u003c/sub\u003eO in total do not exceed 1% by weight, the CaO content is 1.55% wt. and organic parts 0.5%wt. There are also traces of sulphur content (given in the oxide form) \u0026minus;\u0026thinsp;0.1% wt. The total loss on ignition was estimated at 4.46%wt and the average moisture was 8.92%wt.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab1\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eOxide chemical composition of the clay used to produce the aggregate\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"4\" align=\"left\"\u003e\n\u003cp\u003eElement\u003c/p\u003e\n\u003cp\u003e%wt\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eSiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eFe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eTiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eCaO\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eMgO\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eMnO\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e63,67\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e24,06\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3,87\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0,43\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1,55\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1,1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0,02\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eK\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003eO\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eNa\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003eO\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eSO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e3\u003c/strong\u003e\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eP\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003eO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e5\u003c/strong\u003e\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eWater\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eLOI\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eOrganic\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0,4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0,08\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0,1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0,05\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e8,92\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4,46\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0,5\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section3\"\u003e\n\u003ch2\u003e2.1.3 Residues from processing PET bottles\u003c/h2\u003e\n\u003cp\u003eFinding a use and then reusing PET bottles is a very good ecological step, because this product is used on a huge scale all over the world as packaging for various types of drinks and water. Due to their properties, PET packaging decomposes slowly, taking up to several hundred years, so it is important to reuse them. However, over time, through repeated use of the same waste, the material loses its properties and continuous production of bottles is impossible. Therefore, it is important to constantly look for opportunities where each type of waste could be successfully used. The material used in the research is final waste from the recycling process containing PET dust, label remnants (paper, foil) and other post-process residues. Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e shows the chemical composition of PET waste used in the research, obtained using the XRF method. The main ingredients identified were silicon, calcium and iron oxides. No oxides of harmful and toxic elements such as mercury, cadmium or lead were detected. However, this method has limitations in the identification of light elements such as H, O, C. It is these elements that polyethylene terephthalate C\u003csub\u003e10\u003c/sub\u003eH\u003csub\u003e8\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e consists of. The average ash content was determined to be 15.91%wt the remaining compounds burn out.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab2\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eOxide composition of PET waste after calcination\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"4\" align=\"left\"\u003e\n\u003cp\u003eElement\u003c/p\u003e\n\u003cp\u003e%wt\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eMgO\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eSiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eP\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e5\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eSO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eNa\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eK\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2,73\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5,79\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e32,92\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0,76\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0,70\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0,34\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1,44\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eCaO\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eTiO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eMnO\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eFe\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003eO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e3\u003c/strong\u003e\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eCuO\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eZnO\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eSrO\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e45,77\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1,17\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0,49\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6,61\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0,32\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0,60\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0,23\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eThe calorific value of the waste was also tested - this is to improve the efficiency of sintering. The heat of combustion in the dry state Qs amounted to 29590 kJ/kg on average, and the emission of chlorine to the atmosphere was 0.80%wt. The calorific value of waste, PET, generates an exothermic reaction through combustion, which reduces energy consumption in the sintering process. This contributes to savings in the energy demand of the furnace, which results in lower gas emissions into the environment and, therefore, economic savings. The total moisture of the waste was 15.6% by weight. The analysis of the phase composition of the tested waste was very difficult. Only three phases that may be included in the tested material were identified. These are calcite, silica and dolomite (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). The authors decided to provide the quantitative composition of the identified minerals, but it should be taken into account that this is an estimated analysis.\u003c/p\u003e\n\u003cp\u003eSince the ultimate method of aggregate consolidation is sintering, tests using high-temperature microscopy (HSM) were carried out to illustrate changes in the sample geometry. Figure\u0026nbsp;3 shows the research results. In the case of testing PET waste, no temperatures characteristic of sintered materials were observed in the sample. A geometric change called \"corner rounding\" was recorded at 845\u0026deg;C (5% change in sample dimensions) (a). Then the material shrinks and decomposes more and more without sintering. From a temperature of 1160\u0026deg;C, a rapid change in the dimensions of the sample is observed (b,c). At a temperature of 1200\u0026deg;C, only loose ash remains (d), consisting mainly of silica and calcium oxide.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n\u003ch2\u003e2.2 Manufacturing method \u0026ndash; granulation\u003c/h2\u003e\n\u003cp\u003eThe production process of artificial aggregate consists of five stages: grinding of raw materials, usually combined with drying or separate drying of wet raw materials, mixing of raw materials, granulation, classification and hardening. In the first stage, drum and drying ball mills are usually used, in which coarse-grained raw materials are ground. Raw materials can be ground separately or together in appropriate proportions, thanks to which the mixing process takes place. In the second stage, appropriately selected ingredients are mixed until the mixture reaches optimal homogenization, at this stage a binder may also be added if necessary. In the third stage, the mixture of raw materials is subjected to the granulation process by agglomeration of small particles using water and an appropriate binder, if the process requires it. Depending on the appropriately selected operating parameters of the granulator and the moisture content (water dosage), the appropriate size of granules will be produced in the device. In the fourth stage, depending on the type of machines used, granules may be classified according to grain size, and fine-grained products and cracked granules are returned to the granulation process. The hardening of fresh granules in the fifth stage is achieved by drying. The flowchart of lightweight aggregate production can be illustrated in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e. The consolidation process, called structured agglomeration of powders with a high degree of dispersion, aims to combine small dust particles to create larger aggregates (over 1 mm in size) with appropriate properties. This process is used to obtain a form of product that will be convenient for use by recipients or possible for further use in appropriate technologies.\u003c/p\u003e\n\u003cp\u003eDynamic granulation, takes place in dynamic counter-rotating granulators with variable rotation speed of the drum and mixer with opposite directions of rotation (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ea). The machine enables the processing of various types of consistency into selected forms of granules. Mixing and granulation takes place in one device and ensures the highest standards in terms of product quality, energy consumption and efficiency per volume unit of the technological device. The raw materials become cohesive in a very short time - several dozen seconds, and because it is a closed chamber system, dust formation is limited to a minimum. Drum granulation - the process is characterized by continuity thanks to the movement of the granulated material inside an open drum inclined at a small angle (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003eb).\u003c/p\u003e\n\u003cp\u003eTwo methods of producing granules were used in the research. Using a dynamic counter-rotating granulator and a drum granulator. In the first case, the granules were smaller (on average 5 mm in diameter, Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003ea) and the process occurred much faster, within a few minutes. However, in the second one, a smaller number of balls with a coarser fraction was obtained (approximately 10 mm on average, Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003eb). The produced granulates were hardened using a combined method - sintering and hydration.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n\u003ch2\u003e2.3 Hardening process\u003c/h2\u003e\n\u003cdiv id=\"Sec9\" class=\"Section3\"\u003e\n\u003ch2\u003e2.3.1 Sintering\u003c/h2\u003e\n\u003cp\u003eSintering is a basic technological process in the production of materials with a fixed shape. When heated to an appropriate temperature, lower than the melting point, the set of contacting grains bond together, forming a polycrystal. The essence of this process are mass transfer mechanisms that lead to macroscopic changes in the material. These include: reduction of porosity and the accompanying thickening and shrinkage of the sintered system, as well as an increase in its mechanical strength. The basic driving force of the sintering process is the energy of the free surfaces of the set of particles. The specific surface area, which is the total surface area of the particles of crushed material per unit mass, is directly proportional to the susceptibility to sintering. In other words, the finer the mineral fraction, the faster the shape preservation process. The tested materials are fine-grained, so the transport of matter will occur quickly and uniformly (Lis \u003cspan class=\"CitationRef\"\u003e2000\u003c/span\u003e). The samples were fired in an FCF 12SHM electric furnace from Czylok, operating temperature up to 1250 \u003csup\u003eo\u003c/sup\u003eC, working chamber with a capacity of 8 dm\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\n\u003ch2\u003e2.3.2 Hydration\u003c/h2\u003e\n\u003cp\u003eThe hydration process is a multi-stage process. However, it seems that from the point of view of using calcined concrete dust and PET ash as a grout ingredient, the most important thing is the hydration of tricalcium aluminate. This hydration is complicated, and the product of this reaction are hydrated calcium silicates insoluble in water (Kurdowski \u003cspan class=\"CitationRef\"\u003e2010\u003c/span\u003e). To ensure a fully developed hydration process, the samples were maintained in distilled water for 28 days.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n\u003ch2\u003e3.1 Formula selection\u003c/h2\u003e\n\u003cp\u003eIn order to obtain the best product, three mixtures were created containing different amounts of aggregate ingredients, as shown in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab3\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eRaw material compositions of the produced aggregates\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eSample acronym\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eGranulation type\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eClay\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eConcrete dust\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePET residues\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd colspan=\"3\" align=\"left\"\u003e\n\u003cp\u003e%wt\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eI GD\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd rowspan=\"3\" align=\"left\"\u003e\n\u003cp\u003edynamic\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e40\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e30\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e30\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eII GD\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e42\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e42\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e16\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eIII GD\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e32\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e56\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e12\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eI GB\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd rowspan=\"3\" align=\"left\"\u003e\n\u003cp\u003edrum\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e40\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e30\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e30\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eII GB\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e42\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e42\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e16\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eIII GB\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e32\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e56\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e12\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n\u003ch2\u003e3.2 Aggregate before sintering\u003c/h2\u003e\n\u003cp\u003eGenerally, sintering is a three-step process:\u003c/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003estage I \u0026ndash; initial sintering phase \u0026ndash; observed when the material temperature is approximately 0.25 of the melting temperature, no shrinkage is observed at this stage, the original arrangement of layers in the aluminosilicates remains intact, the products are dried with a gradual increase in temperature to 200\u0026deg;C. This process is characterized by the removal of the remaining free water, the content of which in the raw material is still several percent.\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003estage II \u0026ndash; intermediate phase \u0026ndash; occurs when the material temperature is 0.25\u0026ndash;0.75 of the melting point, at this stage the beginning of shrinkage is noticeable, grain growth and material thickening occur. During the second firing period, also called the dehydration period, which includes a further increase in temperature to approximately 600\u0026deg;C, chemically bound water is released. At the same time, the dehydration process decomposes organic substances and begins to decompose chemical compounds and minerals.\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003estage III \u0026ndash; final phase \u0026ndash; end of the thickening phase, transformation of open pores into closed ones and their partial disappearance, with continuous grain growth. This stage, called the vitrification period, is characterized by significant changes in the mineralogical composition of the mass.\u003c/p\u003e\n\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eIn the granule sintering process, attempts were made to prevent stage III from fully developing in order not to close the high porosity of the material. The set temperature was intended to roast (chemically change) raw materials undergoing thermal dissociation. As a result, this was to increase the porosity of the aggregates due to escaping gases and burning of organic parts, which also contributes to a decrease in the apparent density and an increase in the absorbability of the aggregate. Changing these properties will have a positive effect, for example, on the water retention of aggregates. This optimally selected temperature ensures the formation of a durable sinter, and durability is achieved through the glassy phase that sticks the powder particles together. (Lis \u003cspan class=\"CitationRef\"\u003e2000\u003c/span\u003e, Liu 2018,).\u003c/p\u003e\n\u003cp\u003eThe characteristic temperatures of the sinter were determined using a Misura\u0026reg; HSM high-temperature microscope. Cylindrical test samples (\u0026oslash; = 2 mm, h\u0026thinsp;=\u0026thinsp;3 mm) were pressed manually. The heating rate of the samples was 10\u0026deg;C/min. Additionally, Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e shows an example image obtained from a high-temperature microscope.\u003c/p\u003e\n\u003cp\u003eThe measurement involves observing changes in the sample's contours as the temperature increases, which allows the determination of characteristic temperatures, such as:\u003c/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003eSintering temperature Ts \u0026ndash; temperature at which the sample reaches 99% of its initial height;\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eSoftening temperature Tm \u0026ndash; also referred to as the beginning of melting, at which the sample shows a pronounced rounding of the edges;\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eHemisphere temperature Tp \u0026ndash; the height of the sample is half the diameter, it determines the end of its melting;\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eSpreading temperature Tr \u0026ndash; the height of the sample is equal to 1/3 of the initial height (Boccaccini \u003cspan class=\"CitationRef\"\u003e1999\u003c/span\u003e).\u003c/p\u003e\n\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eThe results from the measurement of characteristic temperatures are presented in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e. Samples with extreme clay contents were selected for testing, i.e. sample II with a clay content of 42 wt%, and sample III with a lower clay content of 32 wt%, because this raw material is responsible for obtaining the sinter (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). The granulation process method had no effect on the sintering process. No significant differences were noticed in the sintering process.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab4\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eSummary of characteristic temperature values [\u0026deg;C]\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSample\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eGDII, GBII\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eGDIII, GBIII\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eSintering temperature T\u003cem\u003es\u003c/em\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e970\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e974\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eSoftening temperature T\u003cem\u003em\u003c/em\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e1161\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e1158\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eHemisphere temperature T\u003cem\u003ep\u003c/em\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e1201\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e1198\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eSpreading temperature T\u003cem\u003er\u003c/em\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e1213\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e1215\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eBased on the obtained test results, it was decided to use firing at a temperature of 1000\u0026deg;C (slightly above the minimum sintering temperature). This temperature guarantees obtaining a durable sinter, and at the same time no significant shrinkage of the sample is observed and the porosity does not close.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\n\u003ch2\u003e3.3 Sintered aggregate\u003c/h2\u003e\n\u003cp\u003eThe tested materials have a complex mineralogical composition, hence the sintering system is complicated. The appropriate amount of calcium carbonate in the mass causes the formation of CaO (decarbonation of CaCO\u003csub\u003e3\u003c/sub\u003e), and consequently reduces the viscosity of the liquid phase formed at high temperatures and facilitates the sintering process. The second effect is the formation of pores as a result of decarbonation, which create a network of interconnected channels (open porosity increases). In raw materials with an excess of CaCO\u003csub\u003e3\u003c/sub\u003e, anorthite, calcium aluminates and silicates, and braunmilerite are formed at temperatures above 960\u0026deg;C (Fig.\u0026nbsp;9). The decarbonization reaction of calcite and dolomite proceeds intensively at normal pressure. The presence of dehydrated clay and inorganic admixtures Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, TiO\u003csub\u003e2\u003c/sub\u003e, SiO\u003csub\u003e2\u003c/sub\u003e and others contribute to the acceleration of the decarbonization reaction.\u003c/p\u003e\n\u003cp\u003eThe dehydration of clay minerals is primarily influenced by the firing environment. In addition, the presence of Fe\u003csup\u003e2+\u003c/sup\u003e in clays promotes the formation of new phases. The group of reactions in solid phases of clays that take place through the transport of matter can be described using the following formulas:\u003c/p\u003e\n\u003cp\u003e3(Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u0026middot;2SiO\u003csub\u003e2\u003c/sub\u003e) \u0026rarr; 3(3Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u0026middot;2SiO\u003csub\u003e2\u003c/sub\u003e) + 4SiO\u003csub\u003e2\u003c/sub\u003e, (mullite, cristobalite)\u003c/p\u003e\n\u003cp\u003e4(Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u0026middot;2SiO\u003csub\u003e2\u003c/sub\u003e) + 3Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e \u0026rarr; 4(FeO\u0026middot;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e) + 4(2FeO\u0026middot;SiO\u003csub\u003e2\u003c/sub\u003e) + 7SiO\u003csub\u003e2\u003c/sub\u003e + 1\u003csup\u003e1\u003c/sup\u003e/\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, (hercynite, fayalite, cristobalite)\u003c/p\u003e\n\u003cp\u003e4(Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u0026middot;2SiO\u003csub\u003e2\u003c/sub\u003e)+ 6 FeO \u0026rarr; 4(FeO\u0026middot;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e)+ 4(2FeO\u0026middot;SiO\u003csub\u003e2\u003c/sub\u003e) + 7SiO\u003csub\u003e2\u003c/sub\u003e, (hercynite, fayalite, cristobalite)\u003c/p\u003e\n\u003cp\u003e3(Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u0026middot;2SiO\u003csub\u003e2\u003c/sub\u003e) + 3CaCO\u003csub\u003e3\u003c/sub\u003e + 4SiO\u003csub\u003e2\u003c/sub\u003e \u0026rarr; 3(CaO\u0026middot;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e 2SiO\u003csub\u003e2\u003c/sub\u003e) + 3CO\u003csub\u003e2\u003c/sub\u003e, (anortite)\u003c/p\u003e\n\u003c/div\u003e\n\u003cp\u003eCristobalite formed during firing of montmorillonite-kaolinite raw materials \"loosens the body\" and increases its permeability and water absorption. (Kunag 1997, Nov 2000, Kang \u003cspan class=\"CitationRef\"\u003e2005\u003c/span\u003e, Kłosek 2013, Zawrah 2020).\u003c/p\u003e\n\u003cp\u003eIn order to determine temperature transformations and the mass loss of the tested samples, DSC analyzes were performed. The tests were performed on dried and powdered samples. The measurement results are presented in Fig.\u0026nbsp;9. When roasting clay minerals, structural changes occur, mainly involving the removal of hydroxyl groups from their structures (dehydroxylation) and, consequently, the formation of active forms. Mass loss is recorded in the temperature range 610\u0026ndash;650\u0026deg;C and is caused by dehydroxylation of clay minerals. Dehydroxylation of clay minerals is a complex process that occurs in a wide range of temperatures, even up to 1200\u0026deg;C, where high-temperature swelling is observed. Since the second component was recycled concrete dust, thermal effects will also come from the decomposition of this material. The analyzed thermogram shows a blurred peak starting at a temperature of 250\u0026deg;C up to a temperature of 400\u0026deg;C. In the range of such temperatures, ettringite is completely dehydrated and the dehydration of the C-S-H phase begins. Dehydroxylation of portlandite also partially occurs. It turns into free lime, which allows it to re-bind when in contact with water. At a temperature of 600\u0026deg;C, most of the C-S-H phase decomposes. This makes roasting recycled fines at a temperature level of 650\u0026deg;C a favorable phenomenon. This is related to the binding properties of this fraction and the possibility of using it as a substitute for cement or an active additive to the composite. Weight loss is also observed around 900\u0026ndash;1000\u0026deg;C, so it can be concluded that the samples decompose carbonates and the remains of clay minerals\u003c/p\u003e\n\u003cdiv id=\"Sec19\" class=\"Section2\"\u003e\n\u003ch2\u003e3.3.1 Leaching of soluble compounds and secondary hydration\u003c/h2\u003e\n\u003cp\u003eSamples of fired aggregate with cement dust were subjected to an additional hydration process. The hydration mechanism of calcium aluminates consists of the dissolution process, where the anhydrous phases of clay cement dissolve and then precipitate from the solution in the form of hydrates (chemical compounds from the CaO\u0026middot;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u0026middot;H\u003csub\u003e2\u003c/sub\u003eO system). There are three main phases of the hydration process:\u003c/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003edissolving,\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003enucleation,\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eprecipitation.\u003c/p\u003e\n\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eThe hydration process is initiated by hydroxylation of the cement surface. In the next stage, the cement dissolves in water and releases calcium and aluminum ions into the solution. When the ion concentration exceeds the hydrate solubility level, a small amount of hydrate gel is formed. Dissolution continues with a simultaneous increase in the concentration of calcium and aluminum ions in the water until the saturation level is reached. Crystal nuclei are then formed in large numbers - the nucleation phase. Hydrates begin to precipitate en masse, which leads to a decrease in ion concentration. This is a dynamic process that leads to the dissolution of the rest of the anhydrous cement. In the physical sense, we are dealing with the growth of hydrated crystals that interlock and bond with each other, resulting in the formation of a monolith on a macro scale. The driving force is the lower solubility of hydrates in water than that of anhydrous calcium aluminate. Hydration is a process involving the transfer of ions into solution. This can be confirmed using conductometric measurements. For this purpose, a cement sample is placed in water and tested for ionic conductivity. Its value increases as the number of ions per unit volume increases. For this purpose, tests of the concentrations of substances soluble in water were carried out by performing electrolytic conductivity tests. Additionally, pH changes were monitored. For this purpose, fired aggregate with an appropriate weight of approximately 10 g was immersed in 100 ml of distilled water (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e). Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e shows the measurement results. The parameters of distilled water used for testing were pH 6.04 and conductivity 4.25 \u0026micro;S. Changes in aggregate mass were also recorded after 14 and 28 days, thus checking the condition of the sinter and its resistance to water.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab5\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eResults of measurements of changes in pH and conductivity of solutions\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eTime\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eParameter\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eI GD\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eII GD\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eIII GD\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eI GB\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eII GB\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eIII GB\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd rowspan=\"6\" align=\"left\"\u003e\n\u003cp\u003epH\u003c/p\u003e\n\u003cp\u003e[-]\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e11,00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e11,21\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e11,78\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e11,03\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e11,59\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e11,67\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e10,40\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e11,00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e11,80\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e10,40\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e11,67\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e11,40\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e9,80\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e10,49\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e11,16\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e10,35\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e11,40\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e11,41\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e9,87\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e10,41\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e10,98\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e10,00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e10,91\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e11,03\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 14\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e9,65\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e10,30\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e10,36\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e9,16\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e9,64\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e9,72\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 28\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e9, 34\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e9,87\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e9,90\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e9,16\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e9,56\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e9,60\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd rowspan=\"6\" align=\"left\"\u003e\n\u003cp\u003eConductivity\u003c/p\u003e\n\u003cp\u003e[\u0026micro;S]\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e107\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e175\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e250\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e189\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e184\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e232\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e464\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e482\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e544\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e442\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e431\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e525\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e691\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e723\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e757\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e703\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e699\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e742\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e456\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e480\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e452\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e432\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e460\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e566\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 14\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e250\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e275\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e237\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e189\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e184\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e192\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 28\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e258\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e265\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e243\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e201\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e164\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e132\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eDay 1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDry weight\u003c/p\u003e\n\u003cp\u003e[g]\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e10,6567\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e10,0892\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e10,7055\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e10,0908\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e10,3104\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e10,4344\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"3\" align=\"left\"\u003e\n\u003cp\u003eSaturated weight\u003c/p\u003e\n\u003cp\u003e[g]\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e14,8484\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e15,5041\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e15,7730\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e15,5412\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e15,1895\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e14,4545\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 14\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e15,1304\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e15,6010\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e16,1869\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e15,5705\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e15,2077\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e15,0797\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 28\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e15,2081\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e15,6103\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e16,4311\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e15,6730\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e15,2927\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e15,3022\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eThere are three stages that can occur in an ionic conductivity test:\u003c/p\u003e\n\u003col\u003e\n\u003cli\u003e\n\u003cp\u003eRapid increase in conductivity, associated with a sharp increase in the amount of Ca\u003csup\u003e2+\u003c/sup\u003e and [Al(OH)\u003csub\u003e4\u003c/sub\u003e]\u003csup\u003e\u0026minus;\u003c/sup\u003e ions. During this process, the slow deposition of primary hydrates in the form of a gel is visible.\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eSaturation state - where crystal nuclei are formed\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eCrystallization of hydration products (Kurdowski \u003cspan class=\"CitationRef\"\u003e2010\u003c/span\u003e)\u003c/p\u003e\n\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eThe test results confirm the ongoing hydration process. After mixing the aggregate with water, the liquid phase is rapidly saturated with calcium ions, and the pH of the solution increases rapidly. On the first day of measurement, the highest pH values are observed in the case of aggregates with the highest amount of cement (III GD and III GB; pH above 11. The high pH persists for at least two weeks and in the following days it begins to slowly decrease, but does not reach neutral values. At the same time, with changes in pH, changes in the conductivity of the solution are observed. In the dissolution phase, it is the highest (reaching values above 750 \u0026micro;S in the case of aggregate samples with the highest cement content (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e). About 24 hours after the start of the measurements, the conductivity begins to decrease because crystallizing phases begin to precipitate aluminate, while K+, Na\u0026thinsp;+\u0026thinsp;and OH- ions remain in the solution. Hence the persistently high pH. Crystallization of cement hydration products causes an increase in the mass of the granules (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e). The hydration process also causes additional hardening of the aggregate.\u003c/p\u003e\n\u003cp\u003eAfter 28 days, a second test was carried out in water, and pH and conductivity were similarly measured. For this purpose, aggregate samples were filtered and poured with fresh distilled water with a pH of 6.17 and a conductivity of 6.13 \u0026micro;S. Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e shows the measurement results. The pH indicator is neutral throughout the entire research period, and no increased salt leachability was observed.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab6\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eMeasurements of changes in pH and conductivity of solutions - second measurement series\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eTime\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eParameter\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eI GD\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eII GD\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eIII GD\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eI GB\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eII GB\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eIII GB\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd rowspan=\"4\" align=\"left\"\u003e\n\u003cp\u003epH\u003c/p\u003e\n\u003cp\u003e[-]\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,23\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,12\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,54\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,29\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,70\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,56\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,17\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,28\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,49\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,26\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,48\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,79\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,27\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,18\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,31\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,16\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,32\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,61\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 14\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,02\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,34\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,08\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,34\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e7,50\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd rowspan=\"4\" align=\"left\"\u003e\n\u003cp\u003eConductivity\u003c/p\u003e\n\u003cp\u003e[\u0026micro;S]\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e234\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e219\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e261\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e214\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e221\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e241\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e297\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e278\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e290\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e271\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e256\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e289\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e279\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e281\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e250\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e250\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e242\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e249\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDay 14\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e283\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e275\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e267\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e229\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e256\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e271\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec20\" class=\"Section3\"\u003e\n\u003ch2\u003e3.3.2 Bulk and apparent density\u003c/h2\u003e\n\u003cp\u003eAll obtained granulates had an apparent density below 2g/cm\u003csup\u003e3\u003c/sup\u003e, which meets the standards for classifying the aggregate as light. Slightly lower bulk densities were observed in materials obtained using the drum method - this is due to the coarser and less differentiated aggregate fraction. The lowest densities were obtained in samples of composition III containing 52% of concrete dust, however, these values may change due to the ongoing hydration process. It should be noted, however, that the deviations are small and may be negligible on a larger scale. Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e shows the measurement results.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab7\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 7\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eAverage apparent and bulk densities of the tested samples\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eParameter\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eI GD\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eII GD\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eIII GD\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eI GB\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eII GB\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eIII GB\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eBulk desity\u003c/p\u003e\n\u003cp\u003e[g/cm\u003csup\u003e3\u003c/sup\u003e]\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e0,79\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e0,80\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e0,76\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e0,65\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e0,70\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e0,68\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eApparent density\u003c/p\u003e\n\u003cp\u003e[g/cm\u003csup\u003e3\u003c/sup\u003e]\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e1,43\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e1,43\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e1,31\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e1,39\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e1,35\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e1,23\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec21\" class=\"Section3\"\u003e\n\u003ch2\u003e3.3.3 Kinetics of water release\u003c/h2\u003e\n\u003cp\u003eThe obtained aggregates are very porous, it is open porosity. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e12\u003c/span\u003e shows the dynamics of water absorption.\u003c/p\u003e\n\u003cp\u003eSince the aggregates are intended for use on green roofs, tests were carried out using a precise moisture analyzer with a drying chamber (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e13\u003c/span\u003e), which ensures a uniform drying temperature during measurement. Measurements were carried out at a temperature of 100\u0026deg;C, the average initial weight of the samples was 1.5 g. Tables\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e and \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e present the measurement results.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab8\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 8\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eRecorded water discharge data\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eTime,\u003c/p\u003e\n\u003cp\u003e[min]\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eI GB\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eII GB\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eIII GB\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eI GD\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eII GD\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eIII GD\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003cth colspan=\"7\" align=\"left\"\u003e\n\u003cp\u003e\u003cstrong\u003eLoss of weight\u003c/strong\u003e [%wt]\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e4,3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e4,2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e4,8\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e9,88\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e10,17\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e10,9\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e10\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e11,25\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e9,2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e11,6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e19,76\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e22,12\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e21,99\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e15\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e19,21\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e15,59\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e18,35\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e26,99\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e27,11\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e28,76\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e25,95\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e20,92\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e24,9\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e31,79\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e30,28\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e33,59\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e25\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e29,78\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e25,85\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e31,08\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e34,29\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e38,07\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e43,24\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e30\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e32,84\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e29,39\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\"\u003e\n\u003cp\u003e34,91\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003ctable id=\"Tab9\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 9\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eTotal weight loss depending on time\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eI GB\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eII GB\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eIII GB\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eI GD\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eII GD\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eIII GD\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ecałkowity ubytek masy [%wt]\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e32,86\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e33,83\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e35,89\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e34,45\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e39,02\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e45,62\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eczas końcowy\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e30min 41s\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e35min 18s\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e34min 4 s\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e25min23\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e25min 31s\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e23 min 59s\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eIt turns out that the granulation method affects the rate of water release - granules produced with a drum granulator release water much longer (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e), on average the difference is 8 minutes. This is influenced by both the aggregate fraction and the type and size of porosity. Materials with open porosity will behave differently from those with partially closed porosity. The more open pores, the greater possible water retention. The composition of the samples also influenced the drying dynamics. Interestingly, samples with composition I absorbed the least amount of water, which is justified because they contained the largest amount of clay, which partially forms a glassy phase during sintering, closing the pores.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec22\" class=\"Section3\"\u003e\n\u003ch2\u003e3.3.3 SEM scanning microscopy,\u003c/h2\u003e\n\u003cp\u003eMicrostructure tests of selected aggregates were carried out. Samples of composition II produced by both granulation methods, i.e. drum and dynamic, were selected for testing. The surface and interior of the samples were examined. EDS tests of the materials were also performed. Microscopic photos are shown in Figs. \u003cspan class=\"InternalRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan class=\"InternalRef\"\u003e17\u003c/span\u003e. Porosity is higher in aggregate formed using the dynamic granulation method, the structure is more porous, the grains are less stuck together, this is especially visible at lower magnifications of 50 times - Figs. \u003cspan class=\"InternalRef\"\u003e16\u003c/span\u003e and \u003cspan class=\"InternalRef\"\u003e17\u003c/span\u003e. The aim of the research was to produce a material with high porosity that can absorb large amounts of water. Both granulation methods generally meet these assumptions, however, the microstructure of the GD granules seems to be more favorable.\u003c/p\u003e\n\u003cp\u003eThe GB II sample was selected for testing its chemical composition using EDS energy dispersive spectroscopy - there is no need to test the material made with the second method because the material components and their quantity are the same. Elemental analysis at various points shows that the chemical composition of aggregates is diverse, there are places where there is mainly silica up to 94 wt%, but there are also micro-areas with very different contents of the main oxides, i.e. SiO\u003csub\u003e2\u003c/sub\u003e \u0026minus;\u0026thinsp;44 wt%, CaO \u0026minus;\u0026thinsp;22 wt% Al\u003csub\u003e2\u003c/sub\u003eO3\u0026ndash;17%tue An example analysis is shown in Fig. \u003cspan class=\"InternalRef\"\u003e18\u003c/span\u003e.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThe problem of disposal and management of solid waste materials has become one of the main environmental, economic and social problems. The use of solid waste in the production of lightweight aggregate not only solves the problem of waste disposal, but also helps in transforming waste into useful and profitable products.\u003c/p\u003e\n\u003cp\u003eRecycling PET waste into lightweight aggregates seems to be a feasible solution, not only to the problem of disposal of this type of waste, but also an economical option for the production of lightweight aggregates. Concrete dust from demolition of difficult use is used in this technology as a material that limits plasticity, but also supports hardening through secondary hydration.\u003c/p\u003e\n\u003cp\u003eThe aim of the research was to produce a light aggregate from by-products and waste materials, this goal was achieved, a light and highly porous aggregate was obtained that can be used in various industries, including sustainable architecture (including green roofs).\u003c/p\u003e\n\u003cp\u003eIn further research, the authors will use other plastic raw materials, e.g. clays produced during the washing and processing of gravel, which are so far treated as waste material and stored in water reservoirs.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e: AS - contributed to conceptualization, methodology, validation, formal analysis, investigation, data curation, writing\u0026mdash;original draft, and visualization. TG - contributed to methodology, validation, formal analysis, investigation, data curation, resources, writing\u0026mdash;review and editing, and supervision,\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e:.\u0026nbsp;Research project partly supported by program \u0026bdquo;Excellence initiative \u0026ndash; research university\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInstitutional Review Board Statement\u003c/strong\u003e: Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInformed Consent Statement\u003c/strong\u003e: Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of Interest\u003c/strong\u003e: The authors declare no conflicts of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability Statement\u003c/strong\u003e: The datasets used and/or analyzed during the current study available from the corresponding author on reasonable request\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAbbas, W.; Khalil, W.; Nasser, I. 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Eng. 2021, 42, 102454. https://doi.org/10.1016/j.jobe.2021.102454\u003c/li\u003e\n\u003cli\u003eZawrah, M.F., Badr, H.A. \u0026amp; Khattab, R.M. Recycling and Utilization of some Waste Clays for Production of Sintered Ceramic Bodies. Silicon 12, 1035\u0026ndash;1042 (2020). https://doi.org/10.1007/s12633-019-00193-7\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"artificial lightweight aggregate, green roofs, waste materials recycling, water retention capacity","lastPublishedDoi":"10.21203/rs.3.rs-4214334/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4214334/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eLightweight aggregates are a material used in many industries. A huge amount of this material is used in construction and architecture. For the most part, lightweight construction aggregates are obtained from natural resources such as clay raw materials that have the ability to swell at high temperatures. Resources of these clays are limited and not available everywhere. Therefore, opportunities are being sought to produce lightweight artificial aggregates that have interesting performance characteristics due to their properties. For example, special preparation techniques can reduce or increase the water absorption of such an aggregate depending on the needs and application. The production of artificial lightweight aggregate using various types of waste materials is environmentally friendly as it reduces the depletion of natural resources. Therefore, this article proposes a method of obtaining artificial lightweight aggregate consolidated using two methods: drum and dynamic granulation. Hardening was achieved using combined methods: sintering and hydration, trying to maintain the highest possible porosity. Waste materials were used, such as dust from construction rubble and residues from the processing of PET bottles, as well as clay from the Bełchatów mine as a raw material accompanying the lignite overburden. High open porosity of the aggregates was achieved, above 30%, low apparent density of 1.23 g/cm\u003csup\u003e3\u003c/sup\u003e, low leachability of approximately 250 µS. The produced lightweight aggregates could ultimately be used in green roofs.\u003c/p\u003e","manuscriptTitle":"Artificial lightweight aggregate made from alternative and waste raw materials, hardened using the hybrid method","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-18 18:00:24","doi":"10.21203/rs.3.rs-4214334/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-06-18T04:39:41+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-06-13T10:00:34+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"212780079311343387270510670358726256094","date":"2024-05-22T17:48:08+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-04-24T19:05:38+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"d87ed24e-1ba2-4d97-832c-a887d93f3c43","date":"2024-04-21T16:57:52+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"fa057b19-1c97-4dad-beef-13d6824d5f20","date":"2024-04-19T14:12:05+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"a08709c5-9eca-4c8f-b613-04ed242cc685","date":"2024-04-19T13:59:23+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-04-19T13:42:25+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-04-19T13:39:33+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2024-04-10T16:27:42+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-04-10T10:46:22+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2024-04-03T18:12:53+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"19af2824-514b-4bad-84d5-4e327d4709ba","owner":[],"postedDate":"April 18th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":30659772,"name":"Physical sciences/Engineering/Civil engineering"},{"id":30659773,"name":"Earth and environmental sciences/Environmental sciences"},{"id":30659774,"name":"Physical sciences/Materials science"}],"tags":[],"updatedAt":"2024-08-01T17:05:13+00:00","versionOfRecord":{"articleIdentity":"rs-4214334","link":"https://doi.org/10.1038/s41598-024-67454-3","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2024-07-23 16:15:36","publishedOnDateReadable":"July 23rd, 2024"},"versionCreatedAt":"2024-04-18 18:00:24","video":"","vorDoi":"10.1038/s41598-024-67454-3","vorDoiUrl":"https://doi.org/10.1038/s41598-024-67454-3","workflowStages":[]},"version":"v1","identity":"rs-4214334","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4214334","identity":"rs-4214334","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}