Valorization of geopolymer technology for the production of sulfate resisting normal and lightweight sustainable concrete  

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Khater, Abdeen M. El Naggar, Mahmoud gharieb This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5563148/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The impact of sulfate attack on both regular and lightweight geopolymer concrete, as well as its properties, has been investigated, including the examination of its microstructural behavior over immersion time. The binders used were an equal mix of slag and fly ash, activated with 10 M sodium hydroxide. The control concrete mix design was 1:1.5:2.8 (binder: fine aggregate: coarse aggregate), with aluminum slag partially replacing 10% of the slag to produce lightweight geopolymer concrete. The curing process was conducted in seawater for up to 6 months to assess the stability of the concrete mixes. The characterization of the hardened mixes was performed using XRD, FTIR, and SEM techniques, along with compressive strength and bulk density measurements. The results revealed that the strength of the geopolymer concrete mixes increased for the first month of immersion, followed by a gradual decline over the next 6 months, but still remained equal to or greater than the control (28 days). XRD, FTIR, and SEM analysis confirmed that the three-dimensional geopolymer chains filled most of the matrix pores. However, for the lightweight matrix, voids were more widely distributed within the matrix, which contributed to the decreased density when aluminum slag was used as an additive. Physical sciences/Chemistry Physical sciences/Materials science geopolymer concrete lightweight sulfate Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction The extensive use of cement as a binder in concrete poses significant environmental challenges. Cement production is a major contributor to global carbon dioxide (CO₂) emissions, accounting for approximately 10% of all greenhouse gas emissions worldwide. In 2016 alone, global cement production reached 4 billion tons, resulting in over 50 billion tons of Ordinary Portland Cement (OPC) concrete annually. This massive production releases 0.94 tons of CO₂ per ton of cement, exacerbating global warming and environmental degradation. Additionally, the cement industry consumes 1.5 billion gigajoules of energy annually, further highlighting its environmental impact [ 1 – 4 ]. To address these issues, researchers have explored alternative materials, such as geopolymers, which offer a sustainable and eco-friendly substitute for traditional cement. Geopolymers, first introduced by Davidovits in 1979, are synthesized from silicon (Si)- and aluminum (Al)-rich materials like fly ash, slag, volcanic ash, demolition waste, and kaolin. These materials are activated by alkaline solutions, such as sodium or potassium hydroxide, silicates, or carbonates, to form a durable, three-dimensional polymeric network. Geopolymer concrete exhibits superior mechanical, chemical, and physical properties compared to OPC concrete, including high compressive strength (30–120 MPa), excellent fire resistance, and durability in aggressive environments like acidic or seawater conditions [ 5 – 13 ]. Geopolymer concrete also demonstrates enhanced sulfate resistance and durability compared to OPC concrete, making it a viable alternative for construction in harsh environments. Lightweight aggregates, both natural (e.g., pumice, diatomite, scoria) and synthetic (e.g., expanded clay, perlite, polystyrene), further improve the performance of geopolymer concrete. Lightweight geopolymer concrete reduces structural dead loads, lowers transportation and handling costs, and provides better thermal and acoustic insulation, contributing to energy efficiency in buildings [ 14 – 27 ]. The incorporation of industrial by-products and waste materials, such as metal or plastic waste, into lightweight geopolymer concrete not only reduces costs but also promotes sustainability. Studies have shown that lightweight geopolymer concrete outperforms traditional OPC concrete in terms of durability and environmental impact. For instance, geopolymer concrete maintains its strength and integrity even after prolonged exposure to seawater, whereas OPC concrete degrades significantly under the same conditions [ 28 – 40 ].The use of lower-density concrete offers significant advantages in structural load-bearing capacity, as well as in acoustic and thermal insulation. Density reduction can be achieved by replacing solid constituents with air voids or lightweight aggregates, employing various techniques. For instance, no-fines concrete eliminates fine aggregates, while lightweight concrete replaces conventional aggregates with lighter alternatives. When air voids are introduced into the cement paste, the resulting material is classified as cellular, aerated, or foamed concrete. This approach can reduce raw material usage (sand, cement, and lime) by up to 30%, lowering construction costs [ 41 , 42 ]. Lightweight thermal insulation materials can be broadly categorized into inorganic and organic types: 1. Inorganic Materials a. Fibrous materials: Glass, rock, and slag wool, as well as fly ash. b. Cellular materials: Calcium silicate, bonded perlite, vermiculite, ceramic products, and geopolymers. 2. Organic Materials a. Fibrous materials: Cellulose, cotton, wood pulp, cane, or synthetic fibers. b. Cellular materials: Cork, foamed rubber, polystyrene, polyethylene, polyurethane, polyisocyanurate, and other polymers [43, 44]. Lightweight materials can be produced through various methods. One common approach involves using metallic aluminum powder, which reacts in alkaline environments (e.g., calcium hydroxide or alkaline hydroxides) to release hydrogen gas (H₂). This gas becomes trapped within the cementitious paste, causing expansion and increasing volume. The reaction can be summarized as: 4Al + OH ⁻ + H ₂ O → 2Al ₂ O ⁻ + 3/2 H ₂ To ensure effective gas entrapment, the paste must have an appropriate consistency and rapid setting times [45, 46]. Aluminum slag (dross) is another cost-effective material for producing lightweight components. It introduces air into the composite and can be used to manufacture building blocks, pre-molded panels, subfloors, and other surfaces. Globally, approximately 4 million tons of white dross and over 1 million tons of black dross are generated annually, with 95% being landfilled. However, this material can be repurposed in cement production or as filler in concrete bricks and non-aerated concrete, offering both environmental and economic benefits [47–51]. The main target of the present paper is the preparation of regular or lightweight geopolymer concrete as well as study the influence of sulfate attack on physico-mechanical properties of geopolymer concrete. Also this study focused on the elaboration of the stability of the prepared concrete specimens up on curing in sea water media was up to 6 months, in addition to study mineralogical, mechanical properties and morphological properties of the studied composites 2. Experimental regimes 2.1. Materials The materials employed in this study consist of fly ash (class F) derived from the coal production process, as well as water-cooled slag obtained from the steel manufacturing industry through rapid quenching procedures, sourced from the Iron and Steel Factory located in Helwan, Egypt. Additionally, aluminum slag acquired from the Nagh Hammadi Factory, which specializes in aluminum production in Egypt, is generated during the aluminum recovery process involving scrap recycling, wherein a substantial amount of oxide layer formed on the surface of the molten metal is systematically removed from the melt to enhance the quality of the final output. High-purity sodium hydroxide pellets, with a purity of 99%, sourced from SHIDO Co. in Egypt, were employed as alkali activators in the process. Table 1 presents the chemical compositions of the initial raw materials (1). The characterization of the raw materials was conducted mineralogically through X-ray diffraction analysis in powdered form, as illustrated in Fig. (1). The mineralogical analysis of the fly ash material indicated that its predominant components are mullite and quartz; conversely, water-cooled slag is characterized by its amorphous constituents, as evidenced by the observed pattern. The pattern further illustrated the crystalline characteristics of aluminum slag, wherein a significant proportion of its mineral content is enriched with alumina, including diaoyudaoite, fayalite, spinel, and corundum. The chemical compositions of the initial raw materials are delineated in Table (1), while it is noted that blast furnace slag is an aluminosilicate-rich material composed primarily of SiO 2 , CaO, Al 2 O 3 , Fe 2 O 3 , and MnO, whereas fly ash predominantly contains SiO 2 , Al 2 O 3 , and Fe 2 O 3 as its major constituents. Nonetheless, the chemical composition of aluminum slag exhibits a substantial concentration of Al 2 O 3 , exceeding 75%. 2.2. Geopolymer preparation and curing Geopolymer concrete specimens were prepared by amalgamating raw materials (that successfully passed through a 90 µm sieve) from each mixture with the alkaline solution as delineated in Table (2) in a ratio of 1: 1.5: 2.8 for binder, fine aggregate, and coarse aggregate, respectively, for a duration of 15 minutes utilizing an electronic mixer within a 10 cm cubic mold [ 52 ]. Super-plasticizer type (G) was incorporated in a proportion of 2% relative to the weight of the binder. For the formulation of lightweight concrete, aluminum slag was introduced into the alkaline solution and subsequently mixed with the binding material to enhance the generation of foaming agents. All mixtures were permitted to cure undisturbed at ambient temperature for a period of 24 hours, after which they were subjected to a curing temperature of 40°C with 100% relative humidity for up to 28 days, followed by immersion in a seawater solution for a duration of 6 months. Upon completion of the curing protocol, specimens were extracted from their curing environment, thoroughly dried at 80°C for 24 hours, and subsequently evaluated for compressive strength measurements, while the resulting crushed specimens underwent cessation of the hydration process through the methyl alcohol/acetone method [ 53 , 54 ] to inhibit further hydration, followed by additional drying at 80°C for 24 hours, and finally stored in an airtight container until the time of testing. 2.3. Methods of investigation Chemical analysis was performed using the Axios (PW4400) WD-XRF Sequential Spectrometer from Panalytical, Netherlands. Compressive strength tests were conducted using a five-ton German Brüf pressing machine at a loading rate of 100 kg/min, in accordance with ASTM C109 M standards [ 55 ]. X-ray diffraction (XRD) analysis was carried out using a Philips PW 1050/70 Diffractometer with a Cu-Kα source and a post-sample Kα filter. XRD patterns were obtained by scanning from 0° to 50° 2θ, with a step size of 0.02° 2θ and a scanning speed of 0.4° 2θ/min. Silica was used as an internal standard, and data were analyzed using XRD software (PDF-2: Database on CD-Release 2005). To prevent further hydration, crushed samples were treated with a 1:1 alcohol-acetone solution and washed with acetone, following established protocols [ 53 , 54 ]. Bulk density was calculated using the formula: **Bulk Density = D / (W – S) (g/cm³)** where: - **D** = Weight of the specimen, - **S** = Weight of the suspended specimen in water, - **W** = Weight of the soaked specimen suspended in air [ 56 , 57 ]. Fourier-transform infrared (FTIR) spectroscopy was performed using a Jasco-6100 FTIR spectrometer to analyze the bonding properties of alkali-activated specimens. The test sample was pulverized and mixed with KBr at a 200:1 weight ratio. A 0.20 g mixture was compressed into a 13 mm diameter disc under a pressure of 8 t/cm² and analyzed over a wave number range of 400 to 4000 cm⁻¹ [ 58 , 59 ]. The microstructure and morphology of the geopolymer composites were examined using scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX). Samples were coated with a thin layer of gold prior to analysis to ensure conductivity and image clarity. 3. Results and discussion FTIR spectra for mix incorporating slag/ fly ash normal geopolymer concrete composites (NGCC) immersed in sea water till six months [Figs. (2 and 3)], indicates an the growth of the intensity of geopolymer representative band of asymmetric (T-O-Si) at about 980 cm − 1 [ 60 – 61 ] till one month of immersion followed by gradual degradation in its intensity up to 6 months. This is accompanied by gradual decrease in the intensity of asymmetric band of Si-O-Si for non- solubilized silica at about 1100cm − 1 . The preliminary increase in the previous intensity is due to the continuous dissolution of aluminosilicate forming amorphous geopolymer constituents which reflected positively on the width and intensity of asymmetric band at about 980 cm − 1 . The pattern [Fig. 2] also shows two hydration bands at approximately 3400 and 1600 cm-1, indicating the formation of CSH as well as CASH phases alongside the produced geopolymer phases, which contribute to the additional strength of the composite [ 62 ]. The carbonate bands at 1430 cm − 1 (m C–O) and 867 cm-1 (d C–O) [ 63 ] resulted from the raw materials used as well as the carbonation of unreacted free alkalis [ 66 ]. Other bands identifiable at approximately 796 cm − 1 are ascribed to α-quartz, referencing a prior study [ 60 ], while those at around 780, 725, and 680 cm − 1 correspond to the symmetric stretching of Al-O-Si. Additionally, the bending vibration of Si-O-Si can be detected at approximately 480 cm-1. The subsequent bands demonstrated a decline in intensity over time due to the continuous dissolution and alteration of the aluminosilicate network [ 67 ]. This aligns with the shift of the symmetric stretching vibrations of the Si–O–(Si,Al) bridges to higher wavenumbers (from 719 to 739 cm⁻¹) with increased immersion time up to one month, indicating a modification of the aluminosilicate framework in comparison to a solely MK-based geopolymer as a result of cation substitution in the non-framework sites. Carbonate bands at 1430 cm⁻¹ (ν C–O) and 867 cm⁻¹ (δ C–O) maintained similar intensity, as carbonate constituents in slag materials contribute to the formation of the carbonate band, indicating that the carbonates found in this raw material do not significantly react under alkaline conditions [ 68 ]. In this medium, free alkalis are prone to carbonation, resulting in the formation of trona (Na 3 H(CO 3 ) 2 ·2H 2 O) and natron (Na 2 CO 3 ·10H 2 O). On examining the FTIR pattern of lightweight geopolymer concrete composite (LWGCC) as clarified in Fig. 3, one can notice the continuous growth in the hydration zone at 3450 cm − 1 as well as 1600 cm − 1 for OH vibration band OF CSH &CASH with immersion time as a results of the presence of excess pores in this matrix so can be easily filled with the formed geopolymer and hydration binder. Also, the asymmetric band of vitreous geopolymer content at 980 cm − 1 exposed to gradual increase up to one month with slight shift to low wave number followed by slight decrease with immersion time. The decrease in the main asymmetric band was previously mentioned in the explanation of normal geopolymer concrete composite. Also, we can notice the intensity of the carbonation band is much more intense and broader than the normal geopolymer composite and increase with immersion time, which confirm the increased porosity of the formed matrix. Another important notice is the decrease of the asymmetric vibration of non-solubilized silica at 1100 cm − 1 up to one month as a result of continuous aluminosilicate dissolution. However, further increase in the immersion time lead to the increased shoulder growth at about 1100cm − 1 for non-solubilized silica due to the destabilization of the medium alkalinity up on immersion. This accompanied by the appearance of small shoulder at about 1140 cm − 1 for ettringite which increase with time [ 69 – 71 ]. The mineralogical pattern of a 10% EAFs geopolymer mix immersed in a sulfate solution for up to 6 months is displayed in Fig. 4, where an amorphous band is observed at 60 to 100° 2θ for aluminosilicate gel, along with a relatively small band for amorphous phases in geopolymer within the range of 170 to 350° 2θ. Those areas identified as key characterization regions for geopolymer, where the development of these regions will influence the performance of the resulting composite [ 72 – 73 ]. There is a gradual increase in the intensity of the CSH band up to 1 month, followed by a decrease in broadness and intensity over time up to 6 months, as illustrated by the width at 29. 4°. Also, there is a continuous increase in the albite as well as calcite phases with increasing immersion time beyond one month. The increase of the previous bands may be due to insufficient transformation of aluminosilicate into geopolymer frame work, while unreacted calcite transformed into Trona and natron salts as stated in details in FTIR section. The heightened intensity of C-S-H and the hump in the 17–35° 2θ range can be attributed to increased matrix alkalinity resulting from the hydration process, alongside an enhanced geopolymerization reaction. This interaction occurs as free silica combines with free hydrated calcium oxide within the composites, leading to the formation of C-S-H over time, which subsequently fills and precipitates within empty pores at later curing ages. On studying the effect of aluminum slag as cellular materials to enhance porosity within the matrix, [Fig. 5], an increase in the width of the CSH peak with immersion time up to one month is observed. This is accompanied by an increased intensity within the range of 17–35° (2Θ), indicating the enhanced amorphous geopolymer structure, where the iron cations neutralize the negative charge of the 3D network, resulting in a well-organized and structured geopolymer composite. This will enhance the mechanical properties and offer greater stability against sulfate attack [ 74 , 75 ]. Increasing the immersion time results in heightened peaks of albite and anorthite, along with a reduction in the intensity of CSH and the hump intensity. The increased pore volume within the matrix serves as a barrier to the development of the three-dimensional geopolymer framework, thereby promoting the formation of short chains instead of a 3D network, which subsequently converts into zeolite materials that weaken the matrix. It is understood that the detrimental effects of sulfate exposure include the formation of ettringite at early stages, due to the reaction of free lime produced from the interaction of free calcium with added alkalis and magnesium salt. This reaction leads to the formation of ettringite, which increases internal tension and results in expansion from the original volume, negatively impacting strength, as illustrated in the equations. Figures (6&7) clarify the geopolymer concrete composite’s compressive strength as well as bulk density, where Fig. 6; reflects the increase of strength up to one month then exposed to slight decrease up to 6 month. The recorded behavior is the same for normal as well as lightweight geopolymer concrete composites. The strength values reach almost 23.5 MPa at 1 month then reach to 20 MPa after 6 months of immersion which is almost good and even exceeds the value of unmerged composite; where the decrease in strength did not exceed 15% from the highest strength values for normal concrete. While for lightweight concrete reach to 7.3 MPa after one month of immersion then reaches to 4 MPa which is almost near to control data values; this means the decrease in strength reaches to about 45% from the maximum strength values. The previous strength values for lightweight concrete satisfy the ASTM C330 [ 77 ] where the strength values is from 7–14 MPa. On examining the bulk density behavior of both composites, we can see that the maximum density values is 2.48 g/cm 3 for one month and reaches to 2.42 up on immersion for 6 month for normal concrete composite. However, for lightweight composite reaches 1.97 g/cm 3 at 1 month, decreasing to 1.91 g/cm3 for 6 month of immersion. This means the density values decreased by 23% as compared with the normal control composites. The increased values of compressive strength up to one month were previously declared in XRD as well as FTIR interpretations. The results declare the strength increase along immersion time up to one month as attributed to the continuing pozzolanic reaction in geopolymer concrete composites, while further increase in the immersion time leads to formation of ettringite and suppressing the formation of 3D network as the PH of the medium decreased to lower values as compared with the requested condition for geopolymer formation [ 78 , 79 ]. Figure 8 declared the morphology and microstructure of normal geopolymer concrete composites (NGCC) at 0, 1, 6 months of immersion, the morphology of control mix looks cohesive with little evidence of the presence of unreacted materials, where geopolymer network fill most of the available pore volume leading to formation of homogenous matrix. In spite there were some pores that need to be filled with the formed hardened geopolymer. Immersion to one month (Fig. 8b), there is a noticeable growth in the geopolymer framework leading to an increased compactness with the formation of mostly matrix free from ettringite needle, while the laminar structure of geopolymer increased and spreads within matrix. Extra increase in the immersion till 6 month (Fig, 8c), one can notice the spreading of small pores in addition to medium pores within the matrix with the presence of many micro-cracks forming rough surface is the predominant. All previous remark leads to weaken the matrix cohesion as reflected negatively on the formed geopolymer 3D network which suffered from a pronounced disintegration with time as can be seen clearly from the formed morphological image. On the other hand, the morphological image of lightweight geopolymer concrete composite (LWGCC) (Fig. 9), the main predominant variation is the spreading of wide spherical hollow pores within the matrix as the added alumina slag leads to evolution of free hydrogen molecule up on interacting with the added activator (Fig. 9a). Immersion in sea water for one month (Fig. 9b), leads to further increase in the intensity of the wide pores that partially filled with the geopolymer constituents forming an ideal cellular matrix. Further increase in the immersion time till 6 months (Fig. 9c), form of heterogeneous medium with the spreading of various wide pores that almost free of binder in spite the matrix almost free of ettringite as the geopolymer network inhibit the ingress of sulfate attack. Uniformly distributed micro cracks were also found in the surface of the specimens. 4. Conclusion 1. The research focused on utilizing geopolymer technology to produce sulfate-resistant geopolymer concrete composites. A comparative study was conducted between normal geopolymer concrete composite (NGCC) and lightweight geopolymer concrete composite (LWGCC). 2. FTIR and XRD analyses confirmed the stability of the geopolymer composites against sulfate attack for up to one month. However, prolonged immersion led to a gradual decrease in stability, with minimal evidence of ettringite formation. 3. The compressive strength of normal geopolymer concrete reached approximately 23.5 MPa after one month of immersion and decreased to 20 MPa after six months. This represents a strength reduction of less than 15% from the peak value, which is considered excellent, as it even exceeds the strength of non-immersed composites. 4. For lightweight geopolymer concrete, the compressive strength reached 7.3 MPa after one month and decreased to 4 MPa after six months. This reduction of about 45% from the maximum strength values aligns with the control data and satisfies ASTM C330 [77] standards, which specify a strength range of 7–14 MPa for lightweight concrete. 5. The bulk density of normal geopolymer concrete was 2.48 g/cm³ after one month, decreasing to 2.42 g/cm³ after six months of immersion. For lightweight geopolymer concrete, the density was 1.97 g/cm³ after one month, decreasing to 1.91 g/cm³ after six months. This represents a 23% reduction in density compared to the control composite. Declarations *Conflict of interest: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the paper. *Availability of data and material: "Data is provided within the manuscript” *Funding: there is no source of funding for the current paper. *Authors' contributions: Dr. Hisham M. 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Mohammad, B. Nasrollah, K. Misagh, Bahare M., M. Bahare, A. Farshad, O. Togay , Lightweight geopolymer concrete: A critical review on the feasibility, mixture design, durability properties, and microstructure , Ceramics International , Volume 48, Issue 8,Pages, 10347-10371, 2022 K. Kalinowska-Wichrowska, E. Pawluczuk, M.Bołtryk, A. Nietupski, Geopolymer Concrete with Lightweight Artificial Aggregates. Materials, 15, 3012, 2022. O. Youssf, J.E. Mills, M. Elchalakani, F. Alanazi, A.M. Yosri, Geopolymer Concrete with Lightweight Fine Aggregate: Material Performance and Structural Application. Polymers, 15, 171, 2023. 36. S. T. M. Mohammad, B Nasrollah, K. Misagh, M. Bahare, S. Parham, A. Farshad, O. Togay, Lightweight geopolymer concrete: A critical review on the feasibility, mixture design, durability properties, and microstructure Ceramics International, Volume 48, Issue 8,Pages 10347-10371, 2022. A. Fernandez-Jimenez, I. García-Lodeiro, A. 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In: Properties of concrete, United Kingdom: Wiley, John and Sons, Prentice Hall, 1995: 688–715. E.A. Azimi, M.M. Al Bakri Abdullah, L.Y. Ming, H.C. Yong, Hussin, K. I. Hakem Aziz, Processing and properties of geopolymers as thermal insulating materials: a review, Processing and properties of geopolymers Rev.Adv. Mater. Sci., 2016; 44: 273-285. 44. G. Roviello , C. Menna , O.Tarallo , L. Ricciotti , F. Messina , C. Ferone, D. Asprone, R., Cioffi, Lightweight geopolymer-based hybrid materials, Composites Part B 128 (2017) 225-237. D.L. Bean, P.G. Malore, United States patent 5605570; 1997. C . Vargel, Inorganic bases. In: Vargel C, editor. Corrosion of aluminium. United Kingdom: Elsevier Science; 2004:385–93. O. Hollins, Aluminium industry could dramatically reduce landfilling of furnace, 2002, URL. Access date:[11.11.2007]. M. Brough, , Aluminium Lightens the Environmental Load, Vision-The newsletter of the Foresight and Link Initiative. Winter 2002. No 4. URL. Access date:[11.11.2007]. F. Puertas, M.T. Blanco-Varela, T. Vazquez, Behaviour of cement mortars containing an industrial waste from aluminium refining stability in Ca(OH)2solutions, Cement and Concrete Research, 1999; 29: 1673-1680. D.A. Pereira, B. Aguiar, F. Castro, M.F. Almeida, J.A. Labrincha, Mechanical behaviour of Portland cement mortars with incorporation of Al-containing salt slags, Cement and Concrete Research, 2000; 30: 1131-1138. M. Brough, Aluminium lightens the environmental load”, Vision-The newsletter of theForesight and Link Initiative, No 4, Winter 2002. URL. Access date:[11.11.2007]. D.V.S.P. Rajesh1, Narender Reddy, A. ; Venkata Tilak, U. ; Raghavendra, M., “Performance of alkali activated slag with various alkali activaors’, International Journal of Innovative Research in Science, Engineering and Technology, 2(2); 2013. N. Saikia, A. Usami, S. Kato, T. Kojima, Hydration behavior of ecocement in presence of metakaolin, Resource Progressing Journal, 51(1),35–41(2004). H. M. Khater, “Influence of metakaolin on resistivity of cement mortar to magnesium chloride solution”, Ceramics – Silikáty J., 54(4):325–333(2010). ASTM C109M-12, “Standard Test Method for Compressive Strength of Hydraulic Cement Mortars”, (2012). Egyptian Standards, “Concrete Building Units Used in Non-Load and Load Bearing Walls”, Egyptian Organization for Standardization, Cairo, 1292 (1992) . B. I. Ugheoke, E.O. Onche, O.N. Namessan, G.A. Asikpo, Property Optimization of Kaolin - Rice Husk Insulating Fire - Bricks, Leonardo Electronic Journal of Practices and Technologies, 9,167-178(2006) AS. de Vargas, DC Dal. Molin, ÂB. Masuero, AC. Vilela, J. Castro-Gomes; RM. de Gutierrez, Strength development of alkali-activated fly ash produced with combined NAOH and CA(OH) 2 activators, cement and concrete composites, 2014; 53: 341-349. D. Panias, I.P. Giannopoulou, T. Perraki, Effect of synthesis parameters on the mechanical properties of fly ash-based geopolymers, Colloids and Surfaces A: Physicochem. Eng. Aspects, 301 , 246–254(2007). Alexandre Silva de Vargas, Denise C.C. Dal Molin, Ângela B. Masuero, Antônio C.F. Vilela, Joao Castro-Gomes, Ruby M. Gutierrez, Strength development of alkali-activated fly ash produced with combined NaOH and Ca(OH)2 activators, Cem. Concr. Compos. 53 (2014) 341–349. R.A. Hanna, P.J. Barrie, C.R. Cheeseman, C.D. Hills, P.M. Buchler, R. Perry, Solid state 29Si and 27Al NMR and FTIR study of cement pastes containing industrial wastes and organics, Cem. Concr. Res. 25 (1995) 1435. P .W. Brown, J.V. Bothe, The stability of ettringite, Adv. Cem. Res. 5 (1993) 47– 63. C. Famy, Expansion of heat-cured mortars PhD Thesis, Univ. of London, 1999, p 256. ASTM C109M, (2016) Standard Test Method for Compressive Strength of Hydraulic Cement Mortars. M.Y.A. Mollah, F. Lu, D.L. Cocke, An X-ray diffraction (XRD) and Fourier transform infrared spectroscopic (FT-IR) characterization of the speciation of arsenic(V) in Portland cement type-V, Sci. Total Environ. 224 (1998) 57. 66. H.M.Khater , Abdeen M. El Nagar, “Preparation of Sustainable eco-friendly MWCNT-geopolymer composites with superior sulfate resistance ”, Advanced composites and hybrid materials, springer,Sept 2020; 3: 375-389. https://doi.org/10.1007/s42114-020-00170-4 .[IF = 11.806].Q1 S.A. Bernal, E.D. Rodríguez, R.M. Gutiérrez, J.L. Provis, S. Delvasto, Activation of metakaolin/slag blends using alkaline solutions based on chemically modified silica fume and rice husk ash, Waste Biomass Valor 3 (2012) 99–108. 68. Bernal SA, Provis JL, Rose V, Mejía de Gutiérrez R (2011) Evolution of binder structure in sodium silicate-activated lag metakaolin blends. Cem Concr Compos 33(1):46–54 Ahmed M. Abbas, Mohamed E. Sultan, Hisham M. Khater, Mahmoud M. Abd El-razik, Mohamed A. El-Nawawy, Ahmed Z. Sayed, “ Study Physicochemical and Thermal Properties of Eco-friendly Lightweight Geopolymers Incorporating Silica Sand Flour”, Arabian journal of science and engineering, 48, 7571-7585, https://doi.org/10.1007/s13369-022-07590-y . [IF= 2.807]. Q1 (Jan2023). 70. H.M.Khater , “Preparation and characterization of lightweight geopolymer composites using different aluminium precursors”, építôanyag § Journal of Silicate Based and Composite Materials, Dec. 2018; 70(6) :188-196 , DOI: doi.org/ 10.14382/epitoanyag-jsbcm.2018.33. [IF= 1.1]. H.M.Khater , “Development and characterization of sustainable lightweight geopolymer composites”, Ceramica Journal, 2019; 65: 153-161. [IF=1.085] http://dx.doi.org/10.1590/0366-69132019653732551. Q4 72. H.M.Khater, “Effect of cement kiln dust on Geopolymer composition and its resistance to sulphate attack”, green material journal(ICE); 1(issue (Gmat1)):36-46, March 2013. doi. 10.1680/gmat.12.00003, [ IF=3.564] Q1 H.M.Khater , “Valorization of cement kiln dust in activation and production of hybrid geopolymer composites with durable characteristics”, Advanced composites and hybrid materials, springer,June 2019; 2: 301-311. https://doi.org/10.1007/s42114-019-00097-5 [IF= 11.806], Q1 J. Davidovits, Geopolymers: inorganic polymeric new materials, J. Therm. Anal. 37 (8) (1991) 1633–1656. J. Davidovits, Chemistry of geopolymeric systems terminology, in: Proc. of the 2nd International Conference, 1999, pp. 9–40. S.E. Wallah, B.V. Rangan, Low-calcium fly ash-based geopolymer concrete long-term properties Research Report GC 2, Faculty of Engineering, Curtin University of Technology Perth, Australia, 2006. ASTM C330, C330M, 2023, “Standard Specification for Lightweight Aggregates for Structural Concrete”. H.A.El-Sayed, S.A.Abo El-Enein, H.M.Khater , S.A.Hasanein, “Resistance of Alkali Activated Water Cooled Slag Geopolymer to Sulfate Attack”, Ceramics – Silikáty;55 (2): 153-160 (May2011).[ IF=1.01]. H.M.Khater, Wageeh Ramadan , Mahmoud Ghareib, “Impact of alkali activated mortar incorporating different heavy metals on immobilization proficiency using gamma rays attenuation”, journal of progress in nuclear energy (El Sevier), April 2021; 137 (2021) 103729 . https://doi.org/10.1016/j.pnucene.2021.103729 [IF= 2.461]. Q1 Tables Tables are available in the Supplementary Files section. Additional Declarations No competing interests reported. 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Introduction","content":"\u003cp\u003eThe extensive use of cement as a binder in concrete poses significant environmental challenges. Cement production is a major contributor to global carbon dioxide (CO₂) emissions, accounting for approximately 10% of all greenhouse gas emissions worldwide. In 2016 alone, global cement production reached 4\u0026nbsp;billion tons, resulting in over 50\u0026nbsp;billion tons of Ordinary Portland Cement (OPC) concrete annually. This massive production releases 0.94 tons of CO₂ per ton of cement, exacerbating global warming and environmental degradation. Additionally, the cement industry consumes 1.5\u0026nbsp;billion gigajoules of energy annually, further highlighting its environmental impact [\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTo address these issues, researchers have explored alternative materials, such as geopolymers, which offer a sustainable and eco-friendly substitute for traditional cement. Geopolymers, first introduced by Davidovits in 1979, are synthesized from silicon (Si)- and aluminum (Al)-rich materials like fly ash, slag, volcanic ash, demolition waste, and kaolin. These materials are activated by alkaline solutions, such as sodium or potassium hydroxide, silicates, or carbonates, to form a durable, three-dimensional polymeric network. Geopolymer concrete exhibits superior mechanical, chemical, and physical properties compared to OPC concrete, including high compressive strength (30\u0026ndash;120 MPa), excellent fire resistance, and durability in aggressive environments like acidic or seawater conditions [\u003cspan additionalcitationids=\"CR6 CR7 CR8 CR9 CR10 CR11 CR12\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eGeopolymer concrete also demonstrates enhanced sulfate resistance and durability compared to OPC concrete, making it a viable alternative for construction in harsh environments. Lightweight aggregates, both natural (e.g., pumice, diatomite, scoria) and synthetic (e.g., expanded clay, perlite, polystyrene), further improve the performance of geopolymer concrete. Lightweight geopolymer concrete reduces structural dead loads, lowers transportation and handling costs, and provides better thermal and acoustic insulation, contributing to energy efficiency in buildings [\u003cspan additionalcitationids=\"CR15 CR16 CR17 CR18 CR19 CR20 CR21 CR22 CR23 CR24 CR25 CR26\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe incorporation of industrial by-products and waste materials, such as metal or plastic waste, into lightweight geopolymer concrete not only reduces costs but also promotes sustainability. Studies have shown that lightweight geopolymer concrete outperforms traditional OPC concrete in terms of durability and environmental impact. For instance, geopolymer concrete maintains its strength and integrity even after prolonged exposure to seawater, whereas OPC concrete degrades significantly under the same conditions [\u003cspan additionalcitationids=\"CR29 CR30 CR31 CR32 CR33 CR34 CR35 CR36 CR37 CR38 CR39\" citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e].The use of lower-density concrete offers significant advantages in structural load-bearing capacity, as well as in acoustic and thermal insulation. Density reduction can be achieved by replacing solid constituents with air voids or lightweight aggregates, employing various techniques. For instance, no-fines concrete eliminates fine aggregates, while lightweight concrete replaces conventional aggregates with lighter alternatives. When air voids are introduced into the cement paste, the resulting material is classified as cellular, aerated, or foamed concrete. This approach can reduce raw material usage (sand, cement, and lime) by up to 30%, lowering construction costs [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eLightweight thermal insulation materials can be broadly categorized into inorganic and organic types:\u003c/p\u003e\u003cp\u003e1. \u003cstrong\u003eInorganic Materials\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;a. Fibrous materials: Glass, rock, and slag wool, as well as fly ash.\u003cbr\u003e\u0026nbsp;b. Cellular materials: Calcium silicate, bonded perlite, vermiculite, ceramic products, and geopolymers.\u003c/p\u003e\n\u003cp\u003e2. \u003cstrong\u003eOrganic Materials\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;a. Fibrous materials: Cellulose, cotton, wood pulp, cane, or synthetic fibers.\u003cbr\u003e\u0026nbsp;b. Cellular materials: Cork, foamed rubber, polystyrene, polyethylene, polyurethane, polyisocyanurate, and other polymers [43, 44].\u003c/p\u003e\n\u003cp\u003eLightweight materials can be produced through various methods. One common approach involves using metallic aluminum powder, which reacts in alkaline environments (e.g., calcium hydroxide or alkaline hydroxides) to release hydrogen gas (H₂). This gas becomes trapped within the cementitious paste, causing expansion and increasing volume. The reaction can be summarized as:\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4Al + OH\u003c/strong\u003e\u003cstrong\u003e\u003csup\u003e⁻\u003c/sup\u003e\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;+ H\u003c/strong\u003e\u003cstrong\u003e₂\u003c/strong\u003e\u003cstrong\u003eO \u0026rarr; 2Al\u003c/strong\u003e\u003cstrong\u003e₂\u003c/strong\u003e\u003cstrong\u003eO\u003c/strong\u003e\u003cstrong\u003e\u003csup\u003e⁻\u003c/sup\u003e\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;+ 3/2 H\u003c/strong\u003e\u003cstrong\u003e₂\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;To ensure effective gas entrapment, the paste must have an appropriate consistency and rapid setting times [45, 46].\u003c/p\u003e\n\u003cp\u003eAluminum slag (dross) is another cost-effective material for producing lightweight components. It introduces air into the composite and can be used to manufacture building blocks, pre-molded panels, subfloors, and other surfaces. Globally, approximately 4 million tons of white dross and over 1 million tons of black dross are generated annually, with 95% being landfilled. However, this material can be repurposed in cement production or as filler in concrete bricks and non-aerated concrete, offering both environmental and economic benefits [47\u0026ndash;51].\u003c/p\u003e\n\u003cp\u003eThe main target of the present paper is the preparation of regular or lightweight geopolymer concrete as well as study the influence of sulfate attack on physico-mechanical properties of geopolymer concrete. Also this study focused on the elaboration of the stability of the prepared concrete specimens up on curing in sea water media was up to 6 months, in addition to study mineralogical, mechanical properties and morphological properties of the studied composites\u003c/p\u003e"},{"header":"2. Experimental regimes","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Materials\u003c/h2\u003e \u003cp\u003eThe materials employed in this study consist of fly ash (class F) derived from the coal production process, as well as water-cooled slag obtained from the steel manufacturing industry through rapid quenching procedures, sourced from the Iron and Steel Factory located in Helwan, Egypt. Additionally, aluminum slag acquired from the Nagh Hammadi Factory, which specializes in aluminum production in Egypt, is generated during the aluminum recovery process involving scrap recycling, wherein a substantial amount of oxide layer formed on the surface of the molten metal is systematically removed from the melt to enhance the quality of the final output. High-purity sodium hydroxide pellets, with a purity of 99%, sourced from SHIDO Co. in Egypt, were employed as alkali activators in the process. Table\u0026nbsp;1 presents the chemical compositions of the initial raw materials (1). The characterization of the raw materials was conducted mineralogically through X-ray diffraction analysis in powdered form, as illustrated in Fig.\u0026nbsp;(1).\u003c/p\u003e \u003cp\u003eThe mineralogical analysis of the fly ash material indicated that its predominant components are mullite and quartz; conversely, water-cooled slag is characterized by its amorphous constituents, as evidenced by the observed pattern. The pattern further illustrated the crystalline characteristics of aluminum slag, wherein a significant proportion of its mineral content is enriched with alumina, including diaoyudaoite, fayalite, spinel, and corundum. The chemical compositions of the initial raw materials are delineated in Table\u0026nbsp;(1), while it is noted that blast furnace slag is an aluminosilicate-rich material composed primarily of SiO\u003csub\u003e2\u003c/sub\u003e, CaO, Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, and MnO, whereas fly ash predominantly contains SiO\u003csub\u003e2\u003c/sub\u003e, Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, and Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e as its major constituents. Nonetheless, the chemical composition of aluminum slag exhibits a substantial concentration of Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, exceeding 75%.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Geopolymer preparation and curing\u003c/h2\u003e \u003cp\u003eGeopolymer concrete specimens were prepared by amalgamating raw materials (that successfully passed through a 90 \u0026micro;m sieve) from each mixture with the alkaline solution as delineated in Table\u0026nbsp;(2) in a ratio of 1: 1.5: 2.8 for binder, fine aggregate, and coarse aggregate, respectively, for a duration of 15 minutes utilizing an electronic mixer within a 10 cm cubic mold [\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e]. Super-plasticizer type (G) was incorporated in a proportion of 2% relative to the weight of the binder. For the formulation of lightweight concrete, aluminum slag was introduced into the alkaline solution and subsequently mixed with the binding material to enhance the generation of foaming agents. All mixtures were permitted to cure undisturbed at ambient temperature for a period of 24 hours, after which they were subjected to a curing temperature of 40\u0026deg;C with 100% relative humidity for up to 28 days, followed by immersion in a seawater solution for a duration of 6 months. Upon completion of the curing protocol, specimens were extracted from their curing environment, thoroughly dried at 80\u0026deg;C for 24 hours, and subsequently evaluated for compressive strength measurements, while the resulting crushed specimens underwent cessation of the hydration process through the methyl alcohol/acetone method [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e, \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e] to inhibit further hydration, followed by additional drying at 80\u0026deg;C for 24 hours, and finally stored in an airtight container until the time of testing.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Methods of investigation\u003c/h2\u003e \u003cp\u003eChemical analysis was performed using the Axios (PW4400) WD-XRF Sequential Spectrometer from Panalytical, Netherlands. Compressive strength tests were conducted using a five-ton German Br\u0026uuml;f pressing machine at a loading rate of 100 kg/min, in accordance with ASTM C109 M standards [\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e]. X-ray diffraction (XRD) analysis was carried out using a Philips PW 1050/70 Diffractometer with a Cu-Kα source and a post-sample Kα filter. XRD patterns were obtained by scanning from 0\u0026deg; to 50\u0026deg; 2θ, with a step size of 0.02\u0026deg; 2θ and a scanning speed of 0.4\u0026deg; 2θ/min. Silica was used as an internal standard, and data were analyzed using XRD software (PDF-2: Database on CD-Release 2005).\u003c/p\u003e \u003cp\u003eTo prevent further hydration, crushed samples were treated with a 1:1 alcohol-acetone solution and washed with acetone, following established protocols [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e, \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eBulk density was calculated using the formula:\u003c/p\u003e\u003cp\u003e**Bulk Density\u0026thinsp;=\u0026thinsp;D / (W \u0026ndash; S) (g/cm\u0026sup3;)**\u003c/p\u003e\n\u003cp\u003ewhere:\u003c/p\u003e\n\u003cp\u003e- **D** = Weight of the specimen,\u003c/p\u003e\n\u003cp\u003e- **S** = Weight of the suspended specimen in water,\u003c/p\u003e\n\u003cp\u003e- **W** = Weight of the soaked specimen suspended in air [\u003cspan class=\"CitationRef\"\u003e56\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e57\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eFourier-transform infrared (FTIR) spectroscopy was performed using a Jasco-6100 FTIR spectrometer to analyze the bonding properties of alkali-activated specimens. The test sample was pulverized and mixed with KBr at a 200:1 weight ratio. A 0.20 g mixture was compressed into a 13 mm diameter disc under a pressure of 8 t/cm\u0026sup2; and analyzed over a wave number range of 400 to 4000 cm⁻\u0026sup1; [\u003cspan class=\"CitationRef\"\u003e58\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e59\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eThe microstructure and morphology of the geopolymer composites were examined using scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX). Samples were coated with a thin layer of gold prior to analysis to ensure conductivity and image clarity.\u003c/p\u003e"},{"header":"3. Results and discussion","content":"\u003cp\u003eFTIR spectra for mix incorporating slag/ fly ash normal geopolymer concrete composites (NGCC) immersed in sea water till six months [Figs.\u0026nbsp;(2 and 3)], indicates an the growth of the intensity of geopolymer representative band of asymmetric (T-O-Si) at about 980 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e [\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e] till one month of immersion followed by gradual degradation in its intensity up to 6 months. This is accompanied by gradual decrease in the intensity of asymmetric band of Si-O-Si for non- solubilized silica at about 1100cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe preliminary increase in the previous intensity is due to the continuous dissolution of aluminosilicate forming amorphous geopolymer constituents which reflected positively on the width and intensity of asymmetric band at about 980 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe pattern [Fig.\u0026nbsp;2] also shows two hydration bands at approximately 3400 and 1600 cm-1, indicating the formation of CSH as well as CASH phases alongside the produced geopolymer phases, which contribute to the additional strength of the composite [\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e]. The carbonate bands at 1430 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (m C\u0026ndash;O) and 867 cm-1 (d C\u0026ndash;O) [\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e] resulted from the raw materials used as well as the carbonation of unreacted free alkalis [\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e]. Other bands identifiable at approximately 796 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are ascribed to α-quartz, referencing a prior study [\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e], while those at around 780, 725, and 680 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e correspond to the symmetric stretching of Al-O-Si. Additionally, the bending vibration of Si-O-Si can be detected at approximately 480 cm-1. The subsequent bands demonstrated a decline in intensity over time due to the continuous dissolution and alteration of the aluminosilicate network [\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e]. This aligns with the shift of the symmetric stretching vibrations of the Si\u0026ndash;O\u0026ndash;(Si,Al) bridges to higher wavenumbers (from 719 to 739 cm⁻\u0026sup1;) with increased immersion time up to one month, indicating a modification of the aluminosilicate framework in comparison to a solely MK-based geopolymer as a result of cation substitution in the non-framework sites. Carbonate bands at 1430 cm⁻\u0026sup1; (ν C\u0026ndash;O) and 867 cm⁻\u0026sup1; (δ C\u0026ndash;O) maintained similar intensity, as carbonate constituents in slag materials contribute to the formation of the carbonate band, indicating that the carbonates found in this raw material do not significantly react under alkaline conditions [\u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e68\u003c/span\u003e]. In this medium, free alkalis are prone to carbonation, resulting in the formation of trona (Na\u003csub\u003e3\u003c/sub\u003eH(CO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO) and natron (Na\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e\u0026middot;10H\u003csub\u003e2\u003c/sub\u003eO).\u003c/p\u003e \u003cp\u003eOn examining the FTIR pattern of lightweight geopolymer concrete composite (LWGCC) as clarified in Fig.\u0026nbsp;3, one can notice the continuous growth in the hydration zone at 3450 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e as well as 1600 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for OH vibration band OF CSH \u0026amp;CASH with immersion time as a results of the presence of excess pores in this matrix so can be easily filled with the formed geopolymer and hydration binder. Also, the asymmetric band of vitreous geopolymer content at 980 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e exposed to gradual increase up to one month with slight shift to low wave number followed by slight decrease with immersion time. The decrease in the main asymmetric band was previously mentioned in the explanation of normal geopolymer concrete composite.\u003c/p\u003e \u003cp\u003eAlso, we can notice the intensity of the carbonation band is much more intense and broader than the normal geopolymer composite and increase with immersion time, which confirm the increased porosity of the formed matrix.\u003c/p\u003e \u003cp\u003eAnother important notice is the decrease of the asymmetric vibration of non-solubilized silica at 1100 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e up to one month as a result of continuous aluminosilicate dissolution. However, further increase in the immersion time lead to the increased shoulder growth at about 1100cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for non-solubilized silica due to the destabilization of the medium alkalinity up on immersion. This accompanied by the appearance of small shoulder at about 1140 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for ettringite which increase with time [\u003cspan additionalcitationids=\"CR70\" citationid=\"CR69\" class=\"CitationRef\"\u003e69\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e71\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe mineralogical pattern of a 10% EAFs geopolymer mix immersed in a sulfate solution for up to 6 months is displayed in Fig.\u0026nbsp;4, where an amorphous band is observed at 60 to 100\u0026deg; 2θ for aluminosilicate gel, along with a relatively small band for amorphous phases in geopolymer within the range of 170 to 350\u0026deg; 2θ. Those areas identified as key characterization regions for geopolymer, where the development of these regions will influence the performance of the resulting composite [\u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e72\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e73\u003c/span\u003e]. There is a gradual increase in the intensity of the CSH band up to 1 month, followed by a decrease in broadness and intensity over time up to 6 months, as illustrated by the width at 29. 4\u0026deg;.\u003c/p\u003e \u003cp\u003eAlso, there is a continuous increase in the albite as well as calcite phases with increasing immersion time beyond one month. The increase of the previous bands may be due to insufficient transformation of aluminosilicate into geopolymer frame work, while unreacted calcite transformed into Trona and natron salts as stated in details in FTIR section.\u003c/p\u003e \u003cp\u003eThe heightened intensity of C-S-H and the hump in the 17\u0026ndash;35\u0026deg; 2θ range can be attributed to increased matrix alkalinity resulting from the hydration process, alongside an enhanced geopolymerization reaction. This interaction occurs as free silica combines with free hydrated calcium oxide within the composites, leading to the formation of C-S-H over time, which subsequently fills and precipitates within empty pores at later curing ages.\u003c/p\u003e \u003cp\u003eOn studying the effect of aluminum slag as cellular materials to enhance porosity within the matrix, [Fig.\u0026nbsp;5], an increase in the width of the CSH peak with immersion time up to one month is observed. This is accompanied by an increased intensity within the range of 17\u0026ndash;35\u0026deg; (2Θ), indicating the enhanced amorphous geopolymer structure, where the iron cations neutralize the negative charge of the 3D network, resulting in a well-organized and structured geopolymer composite. This will enhance the mechanical properties and offer greater stability against sulfate attack [\u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e74\u003c/span\u003e, \u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e75\u003c/span\u003e]. Increasing the immersion time results in heightened peaks of albite and anorthite, along with a reduction in the intensity of CSH and the hump intensity. The increased pore volume within the matrix serves as a barrier to the development of the three-dimensional geopolymer framework, thereby promoting the formation of short chains instead of a 3D network, which subsequently converts into zeolite materials that weaken the matrix.\u003c/p\u003e \u003cp\u003eIt is understood that the detrimental effects of sulfate exposure include the formation of ettringite at early stages, due to the reaction of free lime produced from the interaction of free calcium with added alkalis and magnesium salt. This reaction leads to the formation of ettringite, which increases internal tension and results in expansion from the original volume, negatively impacting strength, as illustrated in the equations.\u003c/p\u003e \u003cp\u003e\u003cimg 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8EmA4ziO4ziO46wyfBLgzDR8EYTPAuq/STuO4wwNn4Pm06P8F2A+Ae04yxV0GR3m6zpLAd/o57PpHMfmkEMOCW4I+CIlNmCp6FNvQ8g88SSATzIxQNP38s8999yQmS7IANt4MMbERYHou9BdQTY+Hac4OWdQSZw5Q8810iV93YeSEb5rvvrQtTzHKjsgbvJN/lNxT4LKuQ6MyPbt2xf9m/C2jCl/G0iftJQ2dUT9pqCepHO77bbbIn3jt+KxDn+Ruo7rwlLrvzM9qFN0jTqmvps6bexIrBvoNDZVut6XMfUO+XB18Dnobdu2Fa+99lrl041ptBuVseKvsyeCfNPvqZ458pu65F5rP9oiORQn+cR+1ekA10hrbFuMDqsOZEdTkKYdG1CWtp/kXNesI5zgPBWmS387dLlQpxs2bCjOOOOMYr/99qt8nTYcccQRxWGHHZbV4THJ1VvTuGAQmflEaF9Kgxn+xfPGjRvnrr/++nBOlF3+fTv/Bp77dt111/Cvovm30cCR3/gTJ/+WvQv6N+78q3nFyb+W519J44+8MfyLaa6tW7duwb+n5z5kxOX+bf0QdC3PscoOuIf7KS/yL0gTeZRmX6gXZCPPTdSVQY6x5W8DaZNP6pI0yQfpqp6E6pp6x6neud/CfeimyiOOB6T3OJvvNiy1/jvTAz1Dh9A9tUVczlYQPqUbnFud7MPYeqc4mlDbSfUNdUyr3bS1J4CfwhDe2lnkIq4+eSVe2VXF2aQD07LFKm/yhL4SbyqPygMyc02y46x8wHX8CZ/qq9RnE4Y0uzB0uZAvWy9d4b6UPiBDzi7MKrm8tIH2TDubFrl6Q350C73CSc8IGzOJzBNNAhCSDAjOJWgbUHYUHWfjsShMVyWkoFKFpQKPFUSGPNeQlTdkQaY+kIc6xexSnmOWHffllE3IcPYx3siLXHXlbSFcqnPJMbb8ok4m4o31RGna+qAsiCdX77F86Aj+dXrEdVwXpqH/zmxAZ0N9W1T/Kb3SJKFO5wjTpY2KsfWOtkb8uHiAF6OwdfmMmVa7aWtPgDSxfalrQmG65BXIJ/Fyf0xKB5CZ8GPbYojrQGnHMpHnOC3VI3VlkU7U6TbXCJMr6xRjlAvhJxm8cm9KHyiTLnmbBXJ5aQt5jm3kWKTqjfaFXtl2xjly5XSir8wTTQJShgDBMXhtUONpUvJUo22iroERl1UQOkXCI3cqT4L7CFdnEOqgIdUpZpfyHLPspGh1Db9tmaVAJhm4Nvd3LfOx5Rd1MqXiJN+kaTtzBibxEwCQrsX6ojhifwvXcW2Zlv47/XjxxReDG4pUHdNWqNu4E5E/baoO4qwb0KSYht5xj2xN0/3Ka13bskyz3aTiT9kTkH/TgJD8dh00kgfiTslDecR5nJYthtS9xEv9W3IDJclqkU7U1Z3KpC6PMUOXi+SMdaEtuf4G/eiat6Uml5cucO+k+tiGXL11HRdAX5knmgTEkDjK3fTEBZR5hG6CeG2miZ8Oh/txnMdpyvCnjFwcnxS9ySByn9Ls09jIc6rycuTKc5Ky41wGCEc52bxIyQjThOqg6+wTudVhcH9TmRCmzghbpiG/aCuToKxzTwxjVMexbJRVU5lxHdeWaem/048tW7aEMj/ppJPmXn/99cp3WNCz1CBebbRNG7G6ja6gT7R17ufIb/zF2HpHWOwA90sO2lUOtbkmeyTGlr+JlD2xeW2Tlr2f8Oo3cZRdXBboAdfQFVuXwsY3TVucgvyor2kDuk54i3SiztarjdTplmWMclG95bBjprgtqk+xDj/lyzrySLlyP/EQh8KRBr9lS6zukGdkJCxh1HYog1S54Sd5Y6e6IIzkELm8iLpysBA3YZB7TJrqLUZypfShr8yDTQJIOGU0cmAsEFgV2hYUkPuUDg2cdOPGKwNA2JyiCa7bOOuQArXNpwUZ2t5XV559y04GXGUhpUERhRpnm7j7yEG+FJ5z7iefdXRJY2z5LW3vo5wJ2yUdjBWyxR0Y+oB/nR5xHdeWaem/0w9NAuTWr18/2GQA/VJHGneG/FaadfYzBTYFvZL+Sm9t5zW23pEvhZdd4JhD9rBtGkvVbursiewGrivoAPVGveM0QKEvFfjbQVTd4HSattiCjJQz8nXRW/IV64d0ok4urhGmbVpjlEtdGPpZ8qa2qHGADZ/TfX7jr7wRBzqmsRU6ovwQlmvSG8WF/igelTHhFA/OEstix3LSRY45Xc/lpU05CNk+8jImufRzKM/Kg6WvzINMAsgEicvFhZ9C98SNrglVsDVMUjDrB/y2snEuZbboeupajOJrk8cY4u9SNnLxPX3LjnjiBkdc1q9L/ghDWO5pCx0njVGocVu/mC5pjC2/pc19SkOOBkpjbYK6TdVvHF+da4vCd9X/P//5z3Pbtm2byL399ttVzE6OeBKA23nnnefOP//8icpPtlSODtLaUHs91enUgZ7EnRHxWD/FPYbdRV4rN/lSerm8KL9t01B8Y8ifI27/sT3RdexsF4gDW2wH9SqPeKBPWGyTZIhtuuiSZ8nNPZMiuXDkiYFTE7G+CNsGmlwbPYChy0UypsKoXuN8SQbJrDhimZR+nDfdL3uRshtxXPhhYyya5Nj40Wn8LBqwx3FKDksq/bblYME/jntIJGeq3nLkxgWij8yD/J+Ahx56KHxarSz08PuSSy5p/Y3YNWvWVGft4JNIpdzFwQcfPP9Ztuuuuy5c+89//hOOgjDIVhqoojRU4VOTRx55ZPg0mP3Mkvjggw+qs34giz5JxlGf/JIjbcom9refHYO25dm17C6++OLinXfeCed8xoxyoEzefffd4Gd5//33q7Ph0Gf6SFdceuml4XjTTTeFY1vs59lSn2TrKz91GMeb+1wcZZfyt1DmpQEKOlgaoeLee+8tbr755upqGj4X9vDDDxdXXXVV5bMYdIN2kHIpaCuSj0+Opeiq/yeffHJx9NFHT+Q++clPLii7Po5yTcXd1f3oRz+a2KHjjz322ETur3/9a1XCef73v/8VP/vZz4p99923uOCCC4r33nuvutIe2dJykFSUnXPx/PPPF2eeeWZ1dSFdPzeIDVN758gnECEl56R2N8WNN95YlJ3lvNz0BWVnG87vvPPOcGzDGO1GNMWboq096RIn7L777qFvOPvss+c/W7l+/fpwLbalhL311luLchATypS+CltAHac+WTppX4L+xH1kHeh0OSgtysFk6NtOPfXUxs9tloPRohxoZvWcfFoba530KmasPirHF77whepsB88880woA8Y/kgWnz24/9dRT4dgX2pU9NoHuWHbZZZfqbAcpG3HggQdWZ/3oUw6EnQapekvRZlzQR+bB/lkYjQcDhXGCX/3qV+GYQ43t0UcfDccuYKQYrB133HHFUUcdFYx9HQw6X3311TBwkuH89re/XV3dUXAvv/xyOPaBRn7bbbdVvz401rGxwGimBm90mDF15TlJ2aFIGKerr766OO200xYZMMX9wgsvhOOQ3HXXXcVZZ51V/fqQE088MRwZgKQMZQo6qMsvvzyUHeXJ5EpGfhL5iRd9Il7KnXhBg6XY5TqGGAwfOkgewepJDLrNpO/+++9fZDAngfZi5bOdal/9f/311xfku6t7++23w7fZJ3E//elPi+9///vFl7/85V5u7dq1VW6K4vHHH+/l+JbzlVdeGdwQE6MDDjhgQUd1+umnVxIuxk4GOPbh+OOPL5577rmgB+ioBnJ77rlnOELbtmnRN9ufeOKJ4o477qh8dzCE3U1BG2LgeMopp1Q+H6JBLe0v9RAoxRjtBigXxcs56bSlzp7ss88+4ajBTVewgV/60pfCOX1EHdhF+i4mkdId9FdlO1RfQpvqCoNSdICxAYM//g9EDsLxDXYmQEMxVh+VQgPY1IBauildix1jjFlD5WMnbppoS7+70qccuk6ku1JXbzFtxwW9ZC4LYHBKg9C4xFEOssKyBWG7wHIOyzp2SaRsZCEuu6QTL2EKlq24n/BawiIufts4cxDO3ivILw5ZciBf3fUccXn2LTvtJ+N+Qbz4iS5x695cWVu09FXn4u0Dgms2/7aeAVmVp0nkt0uFnDfFYWVqi3QtB9frlq+l63V6xHWbBnmxeVNdiCH03+nPf//73+RWKTneAVC5p9wnPvGJuXIyNFcOdqoY+6G2Y9sXbQA/azPawDI/dtbqCfHYNjOW3qmN1LmUzVK7UNsas93YeEmvrj3XIRkE8Sotm0Yb2KqBY+sExOUBOVvPPdxLeIUZoi/Bn/T72FpQeeTKl/qoi1tlUBdGstt2Y89hqD4qhWRM6SH55lqTLqTqGnR/nB/JlSIXF35xOabiR1bKRlvdpFu4mJQcqfSVTpc2YeuV49Bu8+bN4djGfhCmzba2unrJMdhKgIXZiGZzOY499tjwVL6slManTMyCeNoGLPMys69bEoGy86zOFsITgrJAw7m2D+mJEU8E6p4QcR3Kgl6w/MVTnNTT/KGIy7Nv2Z133nlh2d9ux4lpGzezdJ42EVZP8+u45ZZbwvJsqXOLHE+SgBWapmVb4AmUxc5+J5HfljF1ysrF0LCFqzRw1a+FkCYrETyZHRLyZfNmn/DCpPrvTMbOO+9cfOUrX8m6T33qU1XIhaBLPAVmReb8888vPv7xj1dX+rH33nuHo9UPrdy1aQvoB+0Kd8011wQ7W6cnY+kd20PLQVPS1rDtA2644YZwrGPMdqN4Kavbb7+99xPZ2J4QL+nAfffdF4518MQakJEn+axm1T1pZAtLassP93AvaJvLpH0JMvE0fRJUzqknyOSDp6u/+c1vKp/hGKuPqoPwMQcddFA4pnQBnZVuzhLU2UUXXRS2Be2xxx7BsdVskjFWn3LQalpuJ8Ck7nOf+1yIP1Vvli7jAsnchcEnARTos88+27i0htH49a9/Hc5Zpq0riCuuuGK+EaTCpfbWoUAa/MYwiQAZdSqZzgF/0kpBvjBINEj2QwoaMRU0Fqny7Ft2GJ0Y4rfYuNlrHF8X6kwJazsNZIk7CX6zl42BQQqUWx0Xk7yusNVLE5tJ5ac+tVfwzTffrHyHgy1cGLgYNfR4goY8qU53Et56660FW+gm0X9n+nz2s58ttmzZEgb/55xzTphEDAHL00zU7cCXwSkPDmgPGjCmQEe3b98e7kW/YlLtcFK9I83Y9mHzGRTn+p8LL7xwfgDWdQA0dLuhzSNryi6n8pYiZU9Ih/QY4NYNMimrww8/PJxTdzG5dx2uvfba6mwh8ZaNSW0x28go4xSpfiYF+aeMGXhbuFcTAJsm5MYNkzBkHxWTKyNga5d0weaLNDds2FAceuihlc/swDZCtg8y6NeAGZ2uK4Mm+paDxiVjUFdvos+4oLPMZQH3ojRcYbm3THB+KQc/lmy6LB1raYy4WLIhDsHyB/HbJeCyYYTwLBWRLsskpIkfS2ZaAuI+/Liu+1lW0rJQSkYbt72HsKUhCc7KAqQjOLdLUDHIm7vepzy7lp3KibBcJ5/kCT9+23Q4J17u4ZpQvFxLyYU/8Sld5QFHWeZQ2ePs0qeW4pAzdT8ypMq0r/yCOEnXlmkM8eQgXWRWGsiOLuJipMOkaR1lgr+FOqsrD/KncrT5tiB3Kl999N8Zn02bNoV6Wbt27dwDDzxQ+faHekb/0THpEG0u10bx4xoyoDtWr9Aj4rF6TXjCqo3hpLfEQ1pWj/roHb+VhsBW8DvVxizKC2Fla4F8SI4UY7UbrltbksobMhOOOIH4c/YEiIP7iYcwNn3OkVVxgewG6XBOWSCT7iePoDKK9YC4cmWva4pbcE48XLOygC0PyWJR3pQvyU/6qiPqNqc73E+eiNs60rGyoKvEa9OykJZkURnFEB9xx/QplxzkGxlSEIfyIF0jbiuT+ln0gvR1jSP+HIkHR56JB3/bfoTuse1I8ZNXdFcQBn/b5yMffhzlVFc2PeJR2du6yeWlTTkIxdG2/PtSV29co7yQzzrKAv+YvjL3ngSAKhBHYfLbVlJbUCoyLMXCKfNWYYDfUhLCUPkyAPgrPErFOQVCOBuvbXAxyI8sUi7do/gsVqmsQ44+9CnPLmVHWSkccXMdheJ3yoARN/42bs7x41oK0kZ2Xdd9cqn8qD6tw488xP7x/eQ9Rx/5LYTtawSQ3eoQ+UnFhSwKk3Jch1RZ4PAXqes4CzLU6VQX/XemAwN/3g0YCuyfbRM5exGD7ti2WmejCMt1nHRYtiHVDrrqHe2XsIQB7td9ciniMDjynrJBljHbjWQXcd6grT2xkC73EY/uo96RM2X/ZItk9yQHvzXIIj+ADtn+ijDWFsUQF/FbveMcv1gWfitM7AR5Qjbdy7FNPvltyzHlKLeUPuEod5HSGVysJ8iRA3nalksdkjdOW1BfKh/iVz1akJPr5Es6y1H3IVOqXGy9x2XCb65bP1wqHpUtuia9i8PgiC91v817Ki/QphwAf2Sw946B8mFlB8pa+Uo5rsf0lTltKZ1eSOGd6UAjHhPqM26cyxnyUtchOY6zmLHbDYO9sW3ZcoY+VQPE5cY065VJ2Uqw7+TBPtm3MIifhi4wUchNEIZmqHrrK/MoLwY7ztjwqT7eMxB1+5X7wJ479nG22be3HGAPLZ/8s/uShy4zx1lpTKPd8B5U/OlkZ/kzdh8Vs3nz5vCp3zbvSswqvA/Auzq5DwDstddexTHHHFP9GgdkKCdvg34yto4h6m0SmX0S4Cw79OIuSq9vqQ8BRlvx8cI1k4CVAEaVsqLMlD9cmy9OOM5qZax2w8TCxscXfmbxe+1Of6jXMfqoOnhxlpdpefE197LxrPPGG2+EF+3pi8kHD+PkLrvssmLr1q2jthUG4g8++GAYmE+LSettUpl3YjmgOnccx3Ecx3GWKQwk+RQmX0SyX/paLjD55pPETKLEunXrihNOOKH28+aTwmD66aefntoKQEyfehtCZp8EOI7jOI7jOM4qw7cDOY7jOI7jOM6qoij+H03EpxgcK6cJAAAAAElFTkSuQmCC\"\u003e\u003c/p\u003e\u003cp\u003eFigures\u0026nbsp;(6\u0026amp;7) clarify the geopolymer concrete composite\u0026rsquo;s compressive strength as well as bulk density, where Fig.\u0026nbsp;6; reflects the increase of strength up to one month then exposed to slight decrease up to 6 month. The recorded behavior is the same for normal as well as lightweight geopolymer concrete composites. The strength values reach almost 23.5 MPa at 1 month then reach to 20 MPa after 6 months of immersion which is almost good and even exceeds the value of unmerged composite; where the decrease in strength did not exceed 15% from the highest strength values for normal concrete. While for lightweight concrete reach to 7.3 MPa after one month of immersion then reaches to 4 MPa which is almost near to control data values; this means the decrease in strength reaches to about 45% from the maximum strength values. The previous strength values for lightweight concrete satisfy the ASTM C330 [\u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e77\u003c/span\u003e] where the strength values is from 7\u0026ndash;14 MPa.\u003c/p\u003e \u003cp\u003eOn examining the bulk density behavior of both composites, we can see that the maximum density values is 2.48 g/cm\u003csup\u003e3\u003c/sup\u003e for one month and reaches to 2.42 up on immersion for 6 month for normal concrete composite. However, for lightweight composite reaches 1.97 g/cm\u003csup\u003e3\u003c/sup\u003e at 1 month, decreasing to 1.91 g/cm3 for 6 month of immersion. This means the density values decreased by 23% as compared with the normal control composites.\u003c/p\u003e \u003cp\u003eThe increased values of compressive strength up to one month were previously declared in XRD as well as FTIR interpretations. The results declare the strength increase along immersion time up to one month as attributed to the continuing pozzolanic reaction in geopolymer concrete composites, while further increase in the immersion time leads to formation of ettringite and suppressing the formation of 3D network as the PH of the medium decreased to lower values as compared with the requested condition for geopolymer formation [\u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e78\u003c/span\u003e, \u003cspan citationid=\"CR79\" class=\"CitationRef\"\u003e79\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;8 declared the morphology and microstructure of normal geopolymer concrete composites (NGCC) at 0, 1, 6 months of immersion, the morphology of control mix looks cohesive with little evidence of the presence of unreacted materials, where geopolymer network fill most of the available pore volume leading to formation of homogenous matrix. In spite there were some pores that need to be filled with the formed hardened geopolymer.\u003c/p\u003e \u003cp\u003eImmersion to one month (Fig.\u0026nbsp;8b), there is a noticeable growth in the geopolymer framework leading to an increased compactness with the formation of mostly matrix free from ettringite needle, while the laminar structure of geopolymer increased and spreads within matrix.\u003c/p\u003e \u003cp\u003eExtra increase in the immersion till 6 month (Fig, 8c), one can notice the spreading of small pores in addition to medium pores within the matrix with the presence of many micro-cracks forming rough surface is the predominant. All previous remark leads to weaken the matrix cohesion as reflected negatively on the formed geopolymer 3D network which suffered from a pronounced disintegration with time as can be seen clearly from the formed morphological image.\u003c/p\u003e \u003cp\u003eOn the other hand, the morphological image of lightweight geopolymer concrete composite (LWGCC) (Fig.\u0026nbsp;9), the main predominant variation is the spreading of wide spherical hollow pores within the matrix as the added alumina slag leads to evolution of free hydrogen molecule up on interacting with the added activator (Fig.\u0026nbsp;9a). Immersion in sea water for one month (Fig.\u0026nbsp;9b), leads to further increase in the intensity of the wide pores that partially filled with the geopolymer constituents forming an ideal cellular matrix.\u003c/p\u003e \u003cp\u003eFurther increase in the immersion time till 6 months (Fig.\u0026nbsp;9c), form of heterogeneous medium with the spreading of various wide pores that almost free of binder in spite the matrix almost free of ettringite as the geopolymer network inhibit the ingress of sulfate attack. Uniformly distributed micro cracks were also found in the surface of the specimens.\u003c/p\u003e\n"},{"header":"4. Conclusion","content":"\u003cp\u003e1. The research focused on utilizing geopolymer technology to produce sulfate-resistant geopolymer concrete composites. A comparative study was conducted between normal geopolymer concrete composite (NGCC) and lightweight geopolymer concrete composite (LWGCC). \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e2. FTIR and XRD analyses confirmed the stability of the geopolymer composites against sulfate attack for up to one month. However, prolonged immersion led to a gradual decrease in stability, with minimal evidence of ettringite formation. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e3. The compressive strength of normal geopolymer concrete reached approximately 23.5 MPa after one month of immersion and decreased to 20 MPa after six months. This represents a strength reduction of less than 15% from the peak value, which is considered excellent, as it even exceeds the strength of non-immersed composites. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e4. For lightweight geopolymer concrete, the compressive strength reached 7.3 MPa after one month and decreased to 4 MPa after six months. This reduction of about 45% from the maximum strength values aligns with the control data and satisfies ASTM C330 [77] standards, which specify a strength range of 7\u0026ndash;14 MPa for lightweight concrete. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e5. The bulk density of normal geopolymer concrete was 2.48 g/cm\u0026sup3; after one month, decreasing to 2.42 g/cm\u0026sup3; after six months of immersion. For lightweight geopolymer concrete, the density was 1.97 g/cm\u0026sup3; after one month, decreasing to 1.91 g/cm\u0026sup3; after six months. This represents a 23% reduction in density compared to the control composite. \u0026nbsp;\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003e*Conflict of interest:\u003c/strong\u003e The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e*Availability of data and material:\u003c/strong\u003e \u003cstrong\u003e\u0026quot;Data is provided within the manuscript\u0026rdquo;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e*Funding:\u0026nbsp;\u003c/strong\u003ethere is no source of funding for the current paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e*Authors\u0026apos; contributions:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDr. Hisham M. Khater:\u0026nbsp;\u003c/strong\u003econtribute for proposing the work of the paper, preparation of the materials, interpretation of the data, writing the manuscript as well as language editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDr. Abdeen M. El Naggar:\u0026nbsp;\u003c/strong\u003econtribute for proposing the work of the paper, preparation of the materials, interpretation of the data, writing the manuscript as well as language editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDr. Mahmoud gharieb:\u0026nbsp;\u003c/strong\u003econtribute for proposing the work of the paper, preparation of the materials, interpretation of the data, writing the manuscript as well as language editing.\u003c/p\u003e\n"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003e\u003cstrong\u003eV. M. John and S. E. Zordan,\u003c/strong\u003e Research \u0026amp; Development methodology for recycling residues as building materials-A proposal, Waste Manag. Ser., vol. 1, no. 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Q1\u003c/strong\u003e\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables are available in the Supplementary Files section.\u003c/p\u003e\n"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"geopolymer, concrete, lightweight, sulfate","lastPublishedDoi":"10.21203/rs.3.rs-5563148/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5563148/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe impact of sulfate attack on both regular and lightweight geopolymer concrete, as well as its properties, has been investigated, including the examination of its microstructural behavior over immersion time. The binders used were an equal mix of slag and fly ash, activated with 10 M sodium hydroxide. The control concrete mix design was 1:1.5:2.8 (binder: fine aggregate: coarse aggregate), with aluminum slag partially replacing 10% of the slag to produce lightweight geopolymer concrete. The curing process was conducted in seawater for up to 6 months to assess the stability of the concrete mixes. The characterization of the hardened mixes was performed using XRD, FTIR, and SEM techniques, along with compressive strength and bulk density measurements. The results revealed that the strength of the geopolymer concrete mixes increased for the first month of immersion, followed by a gradual decline over the next 6 months, but still remained equal to or greater than the control (28 days). XRD, FTIR, and SEM analysis confirmed that the three-dimensional geopolymer chains filled most of the matrix pores. However, for the lightweight matrix, voids were more widely distributed within the matrix, which contributed to the decreased density when aluminum slag was used as an additive.\u003c/p\u003e","manuscriptTitle":"Valorization of geopolymer technology for the production of sulfate resisting normal and lightweight sustainable concrete ","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-02 08:52:45","doi":"10.21203/rs.3.rs-5563148/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"6f094b3e-1231-4333-9ea9-b5ce32ae55f8","owner":[],"postedDate":"April 2nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":46443931,"name":"Physical sciences/Chemistry"},{"id":46443932,"name":"Physical sciences/Materials science"}],"tags":[],"updatedAt":"2025-05-30T07:24:13+00:00","versionOfRecord":[],"versionCreatedAt":"2025-04-02 08:52:45","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5563148","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5563148","identity":"rs-5563148","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}