Effect of treated palm fibers on the mechanical properties of compressed earth bricks stabilized by geopolymer binder based natural pozzolan

Effect of treated palm fibers on the mechanical properties of compressed earth bricks stabilized by geopolymer binder based natural pozzolan | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Effect of treated palm fibers on the mechanical properties of compressed earth bricks stabilized by geopolymer binder based natural pozzolan Rolande Aurelie Tchouateu Kamwa, Joseph Bikoun Mousi, Sylvain Tome, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4200988/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 aim of this work is to study the influence of the palm fibers treated with soda hydroxide solution, on the properties of the compressed earth bricks stabilized with 15% of natural pozzolana based alkaline geopolymer binder. To achieve this objective, mortars composed of treated fibers at different levels (0.1, 0.2, 0.3, 0.4 and 0.5%) for a length of 4 and 16 cm, have been developed. These different mortars with those without fibers were subjected to mechanical (dry compression, wet compression, and flexion), physical (water absorption), mineralogical (XRD, FTIR) and microstructural (SEM/EDX) characterizations after 7 and 90 days. The results obtained show that, in general the addition of fibers improves the mechanical and physical properties of compressed earth bricks stabilized with 15% of alkali-geopolymer binder. In addition, the adding of treated palm fibers does not have an influence on the mineralogical composition of the composite bricks. The observation of the diffractograms of FTIR analysis shows that these fibers have a capacity to sorption water molecules. Furthermore, the optical analysis shows that the binder used perfectly encapsulates the fibers. This situation shows that the treated fibers act perfectly as a filler in the matrix. The maximum dry compressive strength and flexural strength values are obtained with the addition of 0.4% fibers at 90 days and are 8.08 and 5.8 MPa respectively. Furthermore, an additional of 0.4% of palm fibers in earth bricks stabilized by the alkaline geopolymer binder based natural pozzolan is recommended for the construction of buildings. earth brick alkaline stabilization treated palm fibers properties Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 1. Introduction Nowadays, research in the field of eco-construction focuses on the recovery of local materials, such as earth, volcanic ash, and industrial waste; while improving their technological characteristics by adding Portland cement, lime, geopolymer binders, natural and synthetic fibers etc. It is in this context that many studies already carried out on the valorization of local raw materials in the field of construction have identified stabilized compressed earth bricks (CEBs) with Portland cement and geopolymer binder as a promising solution for sustainable construction in Cameroon and many other countries. However, earth bricks stabilized by geopolymer binders, although still little used industrially, have physico-mechanical properties competitive with those stabilized by Portland cement. Moreover, these new materials allow for greater recovery of local raw materials with low energy consumption[ 1 ], [ 2 ]. Our previous [ 3 ], [ 4 ] works carried out on the stabilization of compressed earth bricks by acid and alkaline based natural pozzolan geopolymer binders has shed important light in the field of geopolymerization. This work demonstrates that natural pozzolan based geopolymer binders are effective for stabilizing earth bricks. However, stabilization by acid binder has significantly properties than those obtained by alkaline binder[ 5 ]. This is because the natural pozzolan used as a precursor for the geopolymerization reaction would be more reactive in an acidic medium than in an alkaline medium. Moreover, in view of the work carried out by other authors on geopolymer materials, whether acidic or alkaline, the mechanical properties obtained in an acidic environment remain superior to those obtained in an alkaline medium[ 6 ]. However, the alkaline activator is more sustainable than phosphoric acid activator. Thus, raising the possibility to improve the properties of CEBs stabilized by alkaline geopolymer binders by the addition of vegetables fibers. Studies have demonstrated the effectiveness of adding vegetables fibers (date palm, hemp, corn, millet, oil palm, coconut, barley straw, jute, pineapple, etc.) in improving the properties of CEB. However, Cameroon is an agricultural country with huge oil palm plantations. Annual production is estimated at 230,000 tons per year, which ranks the country 13th in the world in this field. Oil palm plantations occupy more than 14 million hectares in the country's intertropical zone[ 7 ]. Once renewed, the oil palm generates huge waste products such as the fibers that wrap around the trunk. In addition, Oil palm fiber is an important lignocellulosic raw material for the preparation of cost-effective and environment-friendly composite materials. Composite materials are created by combining at least two immiscible materials with a high adhesion capacity, resulting in a new material with properties that the individual components do not possess. This work focuses on the recovery of the oil palm fibers and their valorization in the reinforcement of compressed earth bricks stabilized by alkaline based natural pozzolan geopolymer binders. 2. Materials and methods 2.1 Clay soil and natural pozzolan The clayey soils (CS) used for the produced the compressed earth block were collected in the quarry neighboring at Dibamba, Littoral-Cameroon. Natural pozzolan (PZ), the main amorphous precursor for the geopolymer binder, was previously described and characterized in detail [ 5 ]. Both materials were oven-dried for 24 hours at 105°C before crushing through a pulverization method. Afterwards, the resulting powders were passed through the sieve having sized of 500 and 80 µm for clay soil and pozzolan, respectively. 2.2 Alkaline activator solution and palm fibers Aqueous solution was made by combining 10M of NaOH and Na 2 SiO 3 solutions (28.7% of SiO2, 8.9% of Na2O and 62.4% of H2O) in an equal volume ratio. The resulting solution was maintained for 24 hours before being used in the processing and fabrication of green samples according to the work of R. Tchouateu et al. and Z. Koadri et al respectively [ 4 ], [ 7 ]. The fibers used this work is the by-product derived from the palm leaves (Fig. 1 a), harvested in palm farm neighboring at Dibombari, Littoral-Cameroon. Prior, after collection this biowaste, its defibration was done manually (Fig. 1 b). The obtained fibers were treated using 2.5M of NaOH (for 7 hours) to improve the adhesion of the matrix-fiber interface. Because the nature of the surface and the hydrophobic character of natural fibers result in low mechanical qualities for the end-products, it is critical to treat these fibers to improve these capabilities. After the soda treatment, the fibers are saturated in an acidified solution (Acethic Acid), thoroughly rinsed with tap water to remove all residues of NaOH, air-dried for 24 hours, and cut into two distinct lengths (16 and 4 cm). 2.3 Composite preparation For unstabilized compressed earth bricks (CEB) were made by uniaxial pressing at 8MPa of the homogeneous mixture of clayey soil and fibers. The water and mass ratio is fixed at 0.3. For the formulation of stabilized earth bricks (CEBs0), the following process was used: Powdered clayey soil and natural pozzolan were manually mixed. Afterwards, the activating solution was added, and the obtained mortar was further mixed by 5 minutes. Subsequently the different products were obtained by compressing the mixture to 8 MPa. The ratio liquid and solid is fixed at 1 following the Eq. ( 1 ) $$\frac{alcaline solution}{natural pozzolan}=1$$ 1 The production of composite matrices consists by compressing the prismatic form of mixing alkali activated mortar and various proportions of treated fibers from 0 to 0.5 wt.% at 1.5 cm in relation to the total thickness of samples. The specimens were labelled CEBs0.1, CEBs0.2, CEBs0.3, CEBs0.4 and CEBs0.5 (Table 1 ant Fig. 2 ). Two sets of compressed blocks forms including cubic (4 × 4 × 4 cm3) and prismatic (4 × 4 × 16 cm3), were made using mechanical uniaxial press at 8MPa. The obtained blocks were sealed in plastic bags at room temperature before the curing regime at 7 and 90 days. By the end of the curing, the hardened samples were subjected to various tests. The lignocellulosic wt.% composition of treated palm fibers was assessed using Pycnolab laboratories' chemical procedures. The detailed procedure was described by I. Elfaleh et al [ 10 ] Table 1 Percentage of basic materials for each type of compressed earth brick. samples CEB CEBs0 CEBs0.1 CEBs0.2 CEBs0.3 CEBs0.4 CEBs0.5 Clays soil 100 85 84,9 84.8 84.7 84.6 84.5 Geopolymer binder 0 15 15 15 15 15 15 palm fibers 0 0 0,1 0.2 0.3 0.4 0.5 2.4 Characterization of raw material and composite structures The different fractions of used clayey soils were evaluated the sedimentation techniques for fine particles according to ASTM D79280s standard[ 8 ]. The workability of the soils under the Atterberg limit was done by determining index plasticity values following ASTM D43180 standard[ 9 ]. The potential crystalline phases within the raw materials and the produced blocks were evaluated through Powder X-ray Diffraction (XRD) techniques through the Brucker-AXS D8 Debye-Scherrer type (Cukα, ƛ.= 1.5418 A) 2Ɵ in range 5–70°C. The phase’s identification was carried out using HighScore Plus software. FTIR analysis was performed to identify the various functional groups found in these samples. The KBr technique was used to record infrared spectra using a Bruker Vertex 80v spectrometer. This was done with a resolution of 2 cm − 1 and 16 scans of the pellet from each sample. Each pellet was made by combining roughly 1.2 mg of the material with approximately 200 mg of KBr. The morphological features of the specimens without and with fiber were observed using a Jeol XFlash 6160 Bruker scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). The samples were coated with a thin layer of gold to make them measurable under the microscope. The mechanical properties of crushed earth bricks, including three-point flexural and compressive strengths (Fig. 3 a and b), were tested on wet and dry specimens using a compression test machine from Impact Test, UK with a maximum load capacity of 250 KN. Mean values and standard deviation were calculated using four representative samples for each formulation. Physical properties, including water absorption, were assessed on samples of 4 × 4 x 4 cm 3 . For the water absorption (Fig. 3 c) and wet strengths tests,7 and 90days aged samples were dried and weighted at room temperature until constant mass before being immersed in water at room temperature for 48 hours. In terms of water absorption, after removing the water sample, the mass of the wet samples was weighed and compared to the mass of the dry samples using the ASTM C642-06 standard [ 11 ]. 3. Results and discussion 3.1 Characterization of basic materials Figure 4 a and Fig. 4 b display the diffractogram patterns of clay soil (CS) and natural pozzolan (PZ). The diffractogram of clay soil shows that it is essentially composed of kaolinite (PDF-Nr.-000010527), quartz (PDF-Nr.-010741811), goethite (PDF-Nr.-010771060) and microcline (PDF-Nr.-000190926). As can been seen from Fig. 4 b, the natural pozzolan is predominantly made of phases that include: labradorite (PDF-Nr.-010831372), augite (PDF-Nr.-010781392), anorthite (PDF-Nr.-000411481); diopside (PDF-Nr.-010820460) and hematite (PDF-Nr.-000240072). Table 2 shows physical properties of clay soil, principal material used for the manufacture of different compressed earth bricks (CEB). The particle size distribution shown that, clay soil consisted of 0.29% gravel, 74.22% sand, 2.94% silt and 22.54% clay. According to Atterberg, it is a medium-plastic clay because its plasticity index is between 7 and 17. Moreover, the classification of soils according to their nature, based on the particle size distribution of the sample, its plasticity index (11.47) shown in Table 2 , classified the studied clay as type B5 (acceptable clay soil)[ 12 ]. Table 2 Physical properties of clay soil (CS) Sample gravel Ф>2 mm sand 2>Ф>0.02 mm silt 0.02>Ф>0.002 mm clay Ф<0.002 mm Liquid limit Plastic limit Plasticity index Plasticity Domain CS 0.29 74.22 2.94 22.54 32.11 43.58 11.47 Medium Plastic 3.2 Chemical composition of palm fiber The properties of natural fibers, their mechanical capabilities and weak resistances are influenced by their chemical composition. The chemical composition of palm fibers used in this study is mentioned in Table 3 . Non-treated palm consisted of cellulose (46.8%), hemicellulose (20%) and lignin (30.5%). After cellulose, lignin, which is the second most abundant renewable organic substance on this palm fibers. Generally, the tensile strength and Young’s modulus of fibers increase with an increase in cellulose content and, lignin provides plants with water resistance due to its hydrophobicity and contributes to the rigidity and hardness of materials[ 13 ], [ 14 ]. However, plant fibers have certain drawbacks when combined with polymers. The presence of hydroxyl groups in lignocellulose, plant fibers are hydrophilic, making them incompatible with hydrophobic thermoplastics and prone to moisture damage[ 10 ]. These limitations pose challenges for using plant fibers as polymer reinforcement. To improve adhesion between fibers and the polymer matrix and reduce moisture absorption, surface modifications are typically required. It is the reason of the use of alkaline (NaOH) treatment in this context to enhance fiber-matrix compatibility and improve composite quality[ 7 ], [ 15 ]. As the values mentioned in Table 3 , alkaline treatment considerably reduces the percentage of lignin (30.5 to 15.1%) and hemicellulose (20 to 9%). The reason of the weak reduce of cellulose percentage (46.8 to 40) it is that, the alkaline treatment involves reacting the fiber's hydroxyl functions (-OH) of cellulose with acetyl groups (CH 3 CO − ) to give the fiber a hydrophobic surface[ 16 ]. The reaction of NaOH with cellulose can be represented as follows: Cellulose - OH + NaOH → ( Cellulose - O ) + Na + + H 2 O + impurity (3) Table 3 Chemical characteristics of non-treated and treated palm fibers Constituents (% weight) Non-treated palm fiber Lignin hemicellulose Cellulose 30.5 20 46.8 treated palm fiber 15.1 9 40 3.3 Mechanical characterization of composite materials 3.3.1 Dry compressive strength The compressive strength test was performed after 7 days and 90 days of curing. The results obtained from the dry compression test as a function of the alkaline geopolymer binder percentage (0 and 15%) and curing days (7 and 90 days) are summarized in Fig. 5 a. when curing time further increased from 7 days to 90 days, a weak decrease in compressive strength was observed for the unstabilized bricks. This decrease is due to the formation of crack in the unstabilized earth brick matrix with curing time. However, the adding of the geopolymer binder (natural pozzolan + alkaline solution) and curing days directly affects the compressive strength performance of compressed earth bricks. With the adding of 15% of the geopolymer binder at 90 days the compressive strength of bricks increases considerably. This resistance increases from 0.68 to 2.5 MPa respectively for bricks containing 0% and 15% at 7 days of curing and from 2.5 to 5.5 MPa for bricks with 15% of geopolymer binder at 90 days. It shows that compressive strength of the earth bricks is improved with the addition of binder and the strength of alkaline geopolymer concrete increases with the curing time. The dry compressive strengths of the fiber-free and fiber-stabilized bricks obtained as a function of their content and curing time are shown in Fig. 5 b. The dry compressive strength of the material increases with curing time and with the rate of fiber addition up to 0.4%. This increase is due to the geopolymer binders whose bonds develop and strengthen with time, and to the role played by the fibers as a reinforcement taking over the forces transmitted to the clay soil - geopolymer binder matrix. The decrease in strength at 0.5% of fibers would be due to the fact that there are more fiber-fiber contacts since the wettability of the fibers by the matrix has become low[ 17 ], [ 18 ]. In addition, the matrix formed by the fibers would no longer be in sufficient contact with the clay-binder matrix. Optimum dry compressive strength is achieved for an optimal proportion of 0.4% fibers by weight. At this rate, the resistance is 5.5 MPa compared to the fiber brick which is 8.08 MPa. Furthermore, the increase in resistance for all samples from 7 to 90 days is 3 MPa. This identical increase reflects the fact that the curing time did not have an influence on the treated palm fibers but positively influenced the development of the bonds of the geopolymer binder. This was linked to the alteration with time of some minerals phases present in natural pozzolan and clay soil (i.e. hematite, goethite) in alkaline medium allowing the formation of amorphous phase, sodium aluminosilicate such contributing in reinforcement of geopolymer matrix[ 4 ], [ 19 ]. 3.3.2 Wet compressive strength Figures 6 a and b show respectively the results of wet compressive strength tests of bricks aged of 7 and 90 days with the adding of geopolymer binder and the proportions of palm fibers. The unstabilized bricks with geopolymer binder at 7 days of curing present weak wet compressive strength while, those aged 90 days are destroyed in water. This destruction is due to the fact that the capillarity in the fillers (clays and silt) present in the clay soil used is significant what increases water absorption of this material[ 20 ], [ 21 ]. Due to the linear swelling and/or shrinkage that occurs in the clay material due to its moderately plastic nature, open pores and cracks are created which increase with time (90 days) and therefore increase the water permeability of the bricks. The capillarity and permeability significant of these unstabilized bricks leads to the destruction of the bonds present which leads to weak wet resistance or even the destruction of these materials. Furthermore, and for the same reasons mentioned in section 3.3.1 , the adding of the geopolymer binder (Fig. 6 a) and treated palm fibers (Fig. 6 b) positively affects the wet compressive strength of compressed earth bricks and their stability in humid areas (Fig. 3 c). in addition, a reduction of 75% compared to dry compressive resistance is observed in the case of bricks stabilized with 15% of geopolymer binder, while in the case of stabilized bricks containing palm fibers, this reduction is 65%. The addition of treated palm fibers thus has a real advantage for the water resistance of earth bricks stabilized by an alkaline geopolymer binder. Furthermore the wet strength values of the fibrous composites obtained are significantly higher than that recommended by the standard for construction with earth bricks (< 1 MPa) However, optimum wet compressive strength (3.2 MPa) is achieved for an optimal proportion of 0.4% fibers at 90 days. 3.3.3 Flexural strength The values of flexural strength of the different samples are reported in Figs. 7 a and b. It is noticed that the flexural values are higher for compressed earth bricks stabilized with alkaline geopolymer binder compared to those obtained without stabilization at 7 and 90 days (Fig. 6 a). With regard to CEBs with geopolymer binders, the improvement in their mechanical parameters is attributable to the production of geopolymer gels that bond the particles together, thus making the samples compact and resistant with time[ 22 ]. Furthermore, there is a considerable increase in flexural values with the adding of palm fibers. This resistance ranges from 3.5 MPa for fiber less bricks to 6 MPa for bricks with 0.4% fibers at 90 days. As in the case of compressive strength, the maximum value is obtained with an addition rate of 0.4% fiber. In this case of study where the composites have a fibrous matrix, the flexural strength is a characteristic whose interpretation is related to those of the compressive strength because the reinforcement during the test was placed on the side of the stretched face[ 23 ]. However, the addition of 0.5% fiber (drop point) to improve the mechanical bending behavior of composites is much more important than the improvement in compressive strength because the fibers participate in the seam of cracks during the bending test. 3.3.4 Water absorption Figures 8 a and b show the results of the water absorption of the synthesized compressed earth bricks. Due to the increase in cracks in unstabilized earth brick over time, CEB aged 90 days and without alkaline geopolymer binder were very vulnerable to water and disintegrated completely (Fig. 8 a). The sample stabilized with 15% of geopolymer had excellent cohesion in water and the water absorption value varies for 3. 2 to 2.6% at 7 and 90 days respectively. This observation of decrease of the water absorption rate is related to the maturation of the geopolymer matrix, which becomes more compact over time[ 24 ]. In Fig. 9 b, the water absorption rate for 7-day-old bricks increases with the fiber content, while the water absorption rate decreases for 90-day-old bricks. This is related to the fact that the matrix of 7-day-old materials is not more compact and the fact that, the fibers absorb a very high amount of water, which generates a high mass gain within the composite[ 10 ]. According to the results obtained, time is a favorable factor for the development of strong bonds within the geopolymerized matrix that ensures good fiber-matrix adhesion. 3.4 Mineralogical characterization of composite materials 3.4.1 X-Ray Diffraction analysis Figure 9 displays the diffractogram patterns of unstabilized compressed earth bricks (CEB), stabilized compressed earth bricks with 15% of geopolymer binder (CEBs0) and stabilized compressed earth brick contain 0.4% of palm fiber (CEBs0.4).The phase identification show that CEB consists the same phase identified in the clay soil: kaolinite (PDF-Nr.-000010527), quartz (PDF-Nr.-010741811), goethite (PDF-Nr.-010771060) and microcline (PDF-Nr.-000190926). CEB being made up only of CS and water, this water did not bring any modification to the mineralogy of CS. Furthermore, the addition of 15% of geopolymer binder (natural pozzolan + alkaline solution) justifies the presence of new phases observed on the CEBs0 diffractogram. These new phases come from natural pozzolan used as the main precursor of geopolymerization reaction and correspond to: anorthite (PDF-Nr.-000411481); diopside (PDF-Nr.-010820460); hematite (PDF-Nr.-000240072). Observing the diffractogram of the sample stabilized with a geopolymer binder and containing 0.4% of palm fiber (CEBs0.4), we see that the addition of treated palm fibers does not cause any modification to the mineralogy of the samples. This reflects their non-deterioration after 90 days of curing. The decrease in the intensity of kaolinite peaks located at 12.32 ◦, and 24.91◦ \(\theta\) and the disappearance of goethite peaks located at 21.20◦ and 41.27 ◦ \(\theta\) means that, the kaolinite and goethite contained in clay soil dissolves partially in the activating alkaline solutions to contribute to formation of amorphous phase i.e. geopolymer network which plays the role of stabilizer in the matrix within the different composites (CEBs0 and CEBs0.4)[ 19 ]. In addition, phases such as labradorite (PDF-Nr.-010831372) and augite (PDF-Nr.-010781392), initially present in natural pozzolan are not identified in the composites (CEBs0 and CEBs0.4). This means that alkaline solution, once in contact with precursors dissolves the reactive phases to form the geopolymer network. 3.4.1 FTIR analysis The IR spectra of the composite materials: CEB, CEBs0 and CEBs0.4 are illustrated in Fig. 10 . Bands located at 3623 and 3695 cm − 1 characterized absorption bond belong to the hydroxyl (O–H) group of kaolinite[ 25 ]. The absorption bond present at 3474 cm − 1 on all IR spectra is attributed to the hydroxyl group (O–H) of water molecules[ 26 ]. The band located at 1622 cm − 1 (CEB) and 1661 cm − 1 (CEBs0) on is described to the H-O–H bond of water molecules[ 27 ]. The absence of this band on the spectrum of the sample containing 0.4% of palm fiber (CEBs0.4) reflects the sorption capacity of the water molecules of these fibers. This is consistent with the results obtained in the case of the variation in water absorption of the different samples (section 3.3.4 ). The symmetrical stretching vibration bands at 908, 914, 1031and 1083 cm − 1 correspond to Si-O-T, (T = Si, Al, Fe)[ 28 ]. The absorption band at 687 cm − 1 characterized the bending vibration mode of Fe-OH of goethite[ 28 ]. The decrease of this band (Fe-OH) after alkaline activation is due to the alteration of the minerals (kaolinite and goethite) present in CS[ 19 ]. This analyze corresponds to the observation made in section 3.4.1 . The stretching vibration absorption bands located at 537 cm − 1 is attributed to the Fe-O-T (T = Al, Si, Fe), due to the stretching vibration bands of Fe-O[ 28 ]. After analysis of these spectra, the main aluminosilicate band, located at 1031 cm − 1 and 914 cm − 1 on the sample without stabilization (CEB), shifts respectively to 1037 and 908 cm − 1 on stabilized brick without fiber (CEBs0) and stabilized with 0.4% of fiber (CEBs0.4) spectra. This change show a restructuring of the aluminosilicate during geopolymerization process, a result of the alteration of phases such as kaolinite and goethite [ 3 ], [ 29 ]. The fact that these bands shift at the same wavenumbers for the stabilized sample (CEBs0) and the stabilized sample containing 0.4% of palm fibers (CEBs0.4) reflects the fact that the treated palm fibers do not affect the geopolymerization process. This observation confirms once again that these fibers do not deteriorate after 90 days of curing. The news bands at 1453 cm − 1 on CEBs0 and at 1460 cm − 1 on CEBs0.4 spectra are attributable of O–C–O bond of natrite resulting from the carbonation reaction resulting between CO 2 atmospheric and the free Na + ions[ 5 ], [ 19 ]. 3.4.2. SEM/EDS analysis Figure 11 shows selected micrographs of bricks without (F0) and with (F3) fibers. These images show the cohesion between the binder and the non-reactive phases of earth, sand, and fibers, forming a compact structure. This compactness demonstrates the effectiveness of the geopolymer binders in bonding the components of the composite earth bricks. The fibers are not observed in the matrix even at high magnification, which shows that the binder used perfectly encapsulates the fibers. This situation shows that the treated fibers act perfectly as a filler in the matrix. The cracks observed are the impacts of the loads received by the material during the compressive test. At the interfaces of the crystalline grains, a layer adheres, and the results of the chemical analyses presented on the extreme right of the micrographs show that these layers do not have the same chemical compositions, thus revealing the heterogeneous nature of the brick. The failure to observe the geopolymer chains is due to the fact that the fraction of geopolymer formed causes the earth particles to adhere on a microscopic scale, and the mortar formed in turn adheres the grains of sand and fibers on a macroscopic scale. Conclusion This work focused on the study of the addition of treated palm fibers on the mechanical, mineralogical, and microscopic properties of clay bricks stabilized by a geopolymer binder based on natural pozzolan. First, it has been demonstrated that the alkaline geopolymer binder improves the physic-mechanical properties of clay bricks. Subsequently, the addition of palm fibers has enabled an optimization of these properties without affecting the geopolymerization reaction during which there is formation of the gel that ensures the fiber-matrix adhesion of the composite formed. A study of the mineralogical properties of the 90-day-old matrices showed that the kaolinite and goethite contained in clay soil dissolves partially in the activating alkaline solutions to contribute to formation of amorphous phase and the addition of treated palm fibers to bricks stabilized by an alkaline geopolymer binder does not change the mineralogical composition of the base materials. Furthermore, the optical analysis shows that the binder used perfectly encapsulates the fibers. This situation shows that the treated fibers act perfectly as a filler in the matrix. Thus, this work demonstrates the potential of these composite materials (geopolymerized brick-treated palm fiber) to be used in sustainable and ecological construction applications. However, an additional 0.4% of palm fibers in earth bricks stabilized by the alkaline geopolymer binder based natural pozzolan is recommended for the construction of buildings. Declarations Acknowledgements The authors thank LASOGEMA (IUT-Douala-Cameroon) for extending all the facilities to carry out this research. Author contributions Rolande Aurelie Tchouateu Kamwa, Sylvain Tome, Joseph Bikoun Mousi : Validation, Methodology, Writing - review & editing, Visualization, original draft, Rolande Aurelie Tchouateu Kamwa Joseph Bikoun Mousi, sylvain Tome, Juvenal D Neumaleu : Conceptualization, Methodology, Investigation, Writing - original draft. Sylvain Tome , Rolande Aurelie Tchouateu Kamwa, Martine Gerard: PXRD, FTIR analysis, Validation, Writing - review & editing, Visualization, Rolande Aurelie Tchouateu Kamwa, Tome Sylvain, Juvenal D Neumaleu Joseph Bikoun Mousi : Methodology, Writing review & editing, original draft: Supervision, Methodology, Resources, Jacques Etame, Marie-Annie Etoh : Resources, Supervision Funding The authors of manuscript did not receive any funding and grants for this work. Availability of data and materials All data generated or analyzed during this study are included in this article. Compliance with ethical standards Conflict of interest The authors declare that they have no conflict of interest. Consent to participate Not Applicable Consent for publication Not Applicable References Oti JE, Kinuthia JM (2020) The Development of Stabilised Clay-Hemp Building Material for Sustainability and Low Carbon Use. 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Clays Clay Min 45(2):298–300. 10.1346/ccmn.1997.0450219 Ouedraogo E, Coulibaly O, Ouedraogo A, Messan A (2015) Caractérisation mécanique et thermophysique des blocs de terre comprimée stabilisée au papier (cellulose) et / ou au ciment. Mechanical and Thermophysical Properties of Cement and / or Paper (Cellulose) Stabilized Compressed Clay Bricks, 2, pp. 68–76 Zuluaga R, Luc J, Cruz J, Vélez J, Mondragon I, Gañán P (2009) Cellulose microfibrils from banana rachis: Effect of alkaline treatments on structural and morphological features. Carbohydr Polym 76(1):51–59. 10.1016/j.carbpol.2008.09.024 Christine DA, Séraphin DA, Olivier BM, Edjikémé E (2018) Effet de l’addition de fibres de coco traitées à la potasse sur les propriétés mécaniques des matériaux de construction à base d’argile – ciment. Eur Sci J ESJ 14(36):104–116. 10.19044/esj.2018.v14n36p104 Abdelhak M, Fazia F, Abdelmadjid H (2020) Effet des traitements des fibres de palmier dattier sur le comportement mécanique de l ’ interface fibre-matrice de terre stabilisée, 38, 1, pp. 73–76 Malanda N, Louzolo-kimbembe P, Tamba-nsemi YD (2018) Etude des caractéristiques mécaniques d ’ une brique en terre stabilisée à l ’ aide de la mélasse de canne à sucre, vol. 2, no. January, pp. 1–9 Benmansour N (2015) Développement et caractérisation de composites naturels locaux adaptes à l’isolation thermique dans l’habitat, p. 162 Tome S et al (2023) Efficient sequestration of malachite green in aqueous solution by laterite – rice husk ash – based alkali – activated materials: parameters and mechanism. Environ Sci Pollut Res. 10.1007/s11356-023-27138-3 Kemp SJ, Gillespie MR, Leslie GA, Zwingmann H, Campbell SDG (2019) Clay mineral dating of displacement on the Sronlairig Fault: implications for Mesozoic and Cenozoic tectonic evolution in northern Scotland. Clay Min 54(2):181–196. 10.1180/clm.2019.25 Debieb SKF (2011) ´ risation de la durabilite ´ des be ´ tons recycle ´ s a ` base de Caracte ´ ton concasse ´ s gros et fins granulats de briques et de be Characterization of the durability of recycled concretes using coarse and fine crushed bricks and concrete aggregates, pp. 815–824, 10.1617/s11527-010-9668-7 Kaze RC et al (2017) The corrosion of kaolinite by iron minerals and the effects on geopolymerization Applied Clay Science The corrosion of kaolinite by iron minerals and the effects on geopolymerization, Appl. Clay Sci. , vol. 138, no. March, pp. 48–62, 10.1016/j.clay.2016.12.040 Nematollahi B, Sanjayan J, Chai JXH, Lu TM (2014) Properties of fresh and hardened glass fiber reinforced fly ash based geopolymer concrete. Key Eng Mater 594–595. 10.4028/www.scientific.net/KEM.594-595.629 Criado M, Aperador W, Sobrados I (2016) Microstructural and mechanical properties of alkali activated Colombian raw materials. Mater (Basel) 9(3). 10.3390/ma9030158 Ramadji C, Messan A, Sore SO, Prud’Homme E, Nshimiyimana P (2022) Microstructural Analysis of the Reactivity Parameters of Calcined Clays. Sustain 14(4). 10.3390/su14042308 Tome S et al (2021) Resistance of Alkali-Activated Blended Volcanic Ash-MSWI-FA Mortar in Sulphuric Acid and Artificial Seawater Tome S et al (2022) Structural and Physico-mechanical Investigations of Mine Tailing-Calcined Kaolinite Based Phosphate Geopolymer Binder, Silicon , vol. 14, no. 7, pp. 3563–3570, 10.1007/s12633-021-01137-w Kaze RC et al (2018) Microstructure and engineering properties of Fe 2 O 3 (FeO)-Al 2 O 3 -SiO 2 based geopolymer composites. J Clean Prod 3. 10.1016/j.jclepro.2018.07.171 Tome S, Annie M, Jacques E, Sanjay E (2019) Improved Reactivity of Volcanic Ash using Municipal Solid Incinerator Fly Ash for Alkali-Activated Cement Synthesis. Waste Biomass Valoriz 0(0):0. 10.1007/s12649-019-00604-1 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted 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. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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Kamwa","email":"data:image/png;base64,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","orcid":"","institution":"University of Douala","correspondingAuthor":true,"prefix":"","firstName":"Rolande","middleName":"Aurelie Tchouateu","lastName":"Kamwa","suffix":""},{"id":292935119,"identity":"f2841177-4066-4aed-a928-40ac7b37d6be","order_by":1,"name":"Joseph Bikoun Mousi","email":"","orcid":"","institution":"University of Douala","correspondingAuthor":false,"prefix":"","firstName":"Joseph","middleName":"Bikoun","lastName":"Mousi","suffix":""},{"id":292935120,"identity":"65af4275-1215-4d5e-935a-6c380555fe51","order_by":2,"name":"Sylvain Tome","email":"","orcid":"","institution":"University of Douala","correspondingAuthor":false,"prefix":"","firstName":"Sylvain","middleName":"","lastName":"Tome","suffix":""},{"id":292935121,"identity":"f12e1f46-c395-4af0-925b-d0d3ef6fa508","order_by":3,"name":"Juvenal Giogetti Deutou Nemaleu","email":"","orcid":"","institution":"Local Material Promotion Authority (MIPROMALO)","correspondingAuthor":false,"prefix":"","firstName":"Juvenal","middleName":"Giogetti Deutou","lastName":"Nemaleu","suffix":""},{"id":292935122,"identity":"5490c7a2-0d82-42e4-a94e-a5a33c2badf8","order_by":4,"name":"Martine Gérard","email":"","orcid":"","institution":"Sorbonne University","correspondingAuthor":false,"prefix":"","firstName":"Martine","middleName":"","lastName":"Gérard","suffix":""},{"id":292935123,"identity":"375b9ca9-816e-44ff-b2a0-12d267879711","order_by":5,"name":"Marie-Annie Etoh","email":"","orcid":"","institution":"University of Douala","correspondingAuthor":false,"prefix":"","firstName":"Marie-Annie","middleName":"","lastName":"Etoh","suffix":""},{"id":292935124,"identity":"d960a294-eb78-442a-8dc1-977d605cb2f9","order_by":6,"name":"Jacques Etame","email":"","orcid":"","institution":"University Institute of Technology (IUT), University of Douala","correspondingAuthor":false,"prefix":"","firstName":"Jacques","middleName":"","lastName":"Etame","suffix":""}],"badges":[],"createdAt":"2024-04-01 13:37:35","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4200988/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4200988/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":55066841,"identity":"4b2e7c15-4c72-4ac0-b187-797e85305260","added_by":"auto","created_at":"2024-04-22 04:44:01","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1866799,"visible":true,"origin":"","legend":"\u003cp\u003eFiber collection (a), defibration (b), soda treatment (c), drying (d) and measurement (e)\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4200988/v1/e3e1717f5df1fa0885160d57.png"},{"id":55066645,"identity":"5786af52-b127-4714-906a-ed23f09d5ee4","added_by":"auto","created_at":"2024-04-22 04:36:01","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1260047,"visible":true,"origin":"","legend":"\u003cp\u003eRepresentative images of the arrangement of palm fibers (a) and different bricks (b).\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4200988/v1/8ce35895bd9b2fe44b759bc9.png"},{"id":55066649,"identity":"49e13053-69a5-4135-b08b-e82fb977291a","added_by":"auto","created_at":"2024-04-22 04:36:01","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1140980,"visible":true,"origin":"","legend":"\u003cp\u003eFlexural (a), compression (b) and water absorption tests (c).\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-4200988/v1/30333ece8bf852dc699b4f4e.png"},{"id":55066842,"identity":"402f341c-a3ba-4749-8a6d-5fe5f2ce3718","added_by":"auto","created_at":"2024-04-22 04:44:01","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":620615,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea:\u003c/strong\u003e XRD patterns of clay soil (CS)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eb:\u003c/strong\u003e XRD patterns of natural pozzolan (PZ).\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4200988/v1/40c4b51491c12463bc20aa9f.png"},{"id":55066643,"identity":"989328af-7ff9-4070-88b1-dad9dcd8fd8b","added_by":"auto","created_at":"2024-04-22 04:36:01","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":440915,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea: \u003c/strong\u003eVariations of dry compressive strength with geopolymer binder and curing time.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eb: \u003c/strong\u003eVariations of dry compressive strength with palm fibers and curing time.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-4200988/v1/914d34fe9ee1b1678d6b6470.png"},{"id":55066652,"identity":"9a6708db-f47d-4abd-b1a1-a38952b79ad3","added_by":"auto","created_at":"2024-04-22 04:36:01","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":606302,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea: \u003c/strong\u003eVariations of wet compressive strength with geopolymer binder and curing time.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eb: \u003c/strong\u003eVariations of wet compressive strength with palm fibers and curing time.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-4200988/v1/b6764738868baa6d2af7beab.png"},{"id":55066648,"identity":"3f1d77b8-15f4-4983-8427-31349b30371f","added_by":"auto","created_at":"2024-04-22 04:36:01","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":487997,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea: \u003c/strong\u003eVariations of flexural strength with geopolymer binder and curing time.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eb: \u003c/strong\u003eVariations of flexural strength with palm fibers and curing time.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-4200988/v1/d4e47184793c05cbe8ffea4f.png"},{"id":55066843,"identity":"b9ed0c86-dd43-4267-925a-f416c699232f","added_by":"auto","created_at":"2024-04-22 04:44:01","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":415199,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea: \u003c/strong\u003eVariations of water absorption with geopolymer binder and curing time.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eb: \u003c/strong\u003eVariations of water absorption with palm fibers and curing time.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-4200988/v1/b3dfc65bdc77537d31284f6f.png"},{"id":55066646,"identity":"fd1462b3-8032-426b-941f-8f1c654573c7","added_by":"auto","created_at":"2024-04-22 04:36:01","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":738905,"visible":true,"origin":"","legend":"\u003cp\u003eXRD of the powder of different compressed earth bricks.\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-4200988/v1/bbb3996bdfdae62a76e0e879.png"},{"id":55066653,"identity":"3dd775f9-945f-4edd-a453-2545119410fe","added_by":"auto","created_at":"2024-04-22 04:36:01","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":806489,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR spectra of the powder of different compressed earth bricks.\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-4200988/v1/de84a184d934665c3d1c07da.png"},{"id":55066651,"identity":"32049404-16c1-45d6-9203-5ad60507d6db","added_by":"auto","created_at":"2024-04-22 04:36:01","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":795569,"visible":true,"origin":"","legend":"\u003cp\u003emicrographs and EDX analysis of sample.\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-4200988/v1/bd0c2fb9eb25bd768ddaa6dd.png"},{"id":55067344,"identity":"aaaaee5d-0996-4c95-812f-0b7bc0866dc7","added_by":"auto","created_at":"2024-04-22 05:00:10","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":7652744,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4200988/v1/c69b9389-4a5c-4620-b3fe-c4bf12cfe4a1.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Effect of treated palm fibers on the mechanical properties of compressed earth bricks stabilized by geopolymer binder based natural pozzolan","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eNowadays, research in the field of eco-construction focuses on the recovery of local materials, such as earth, volcanic ash, and industrial waste; while improving their technological characteristics by adding Portland cement, lime, geopolymer binders, natural and synthetic fibers etc. It is in this context that many studies already carried out on the valorization of local raw materials in the field of construction have identified stabilized compressed earth bricks (CEBs) with Portland cement and geopolymer binder as a promising solution for sustainable construction in Cameroon and many other countries. However, earth bricks stabilized by geopolymer binders, although still little used industrially, have physico-mechanical properties competitive with those stabilized by Portland cement. Moreover, these new materials allow for greater recovery of local raw materials with low energy consumption[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e], [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOur previous [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e] works carried out on the stabilization of compressed earth bricks by acid and alkaline based natural pozzolan geopolymer binders has shed important light in the field of geopolymerization. This work demonstrates that natural pozzolan based geopolymer binders are effective for stabilizing earth bricks. However, stabilization by acid binder has significantly properties than those obtained by alkaline binder[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. This is because the natural pozzolan used as a precursor for the geopolymerization reaction would be more reactive in an acidic medium than in an alkaline medium. Moreover, in view of the work carried out by other authors on geopolymer materials, whether acidic or alkaline, the mechanical properties obtained in an acidic environment remain superior to those obtained in an alkaline medium[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. However, the alkaline activator is more sustainable than phosphoric acid activator. Thus, raising the possibility to improve the properties of CEBs stabilized by alkaline geopolymer binders by the addition of vegetables fibers. Studies have demonstrated the effectiveness of adding vegetables fibers (date palm, hemp, corn, millet, oil palm, coconut, barley straw, jute, pineapple, etc.) in improving the properties of CEB. However, Cameroon is an agricultural country with huge oil palm plantations. Annual production is estimated at 230,000 tons per year, which ranks the country 13th in the world in this field. Oil palm plantations occupy more than 14\u0026nbsp;million hectares in the country's intertropical zone[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Once renewed, the oil palm generates huge waste products such as the fibers that wrap around the trunk. In addition, Oil palm fiber is an important lignocellulosic raw material for the preparation of cost-effective and environment-friendly composite materials. Composite materials are created by combining at least two immiscible materials with a high adhesion capacity, resulting in a new material with properties that the individual components do not possess. This work focuses on the recovery of the oil palm fibers and their valorization in the reinforcement of compressed earth bricks stabilized by alkaline based natural pozzolan geopolymer binders.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Clay soil and natural pozzolan\u003c/h2\u003e \u003cp\u003eThe clayey soils (CS) used for the produced the compressed earth block were collected in the quarry neighboring at Dibamba, Littoral-Cameroon. Natural pozzolan (PZ), the main amorphous precursor for the geopolymer binder, was previously described and characterized in detail [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Both materials were oven-dried for 24 hours at 105\u0026deg;C before crushing through a pulverization method. Afterwards, the resulting powders were passed through the sieve having sized of 500 and 80 \u0026micro;m for clay soil and pozzolan, respectively.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Alkaline activator solution and palm fibers\u003c/h2\u003e \u003cp\u003eAqueous solution was made by combining 10M of NaOH and Na\u003csub\u003e2\u003c/sub\u003eSiO\u003csub\u003e3\u003c/sub\u003e solutions (28.7% of SiO2, 8.9% of Na2O and 62.4% of H2O) in an equal volume ratio. The resulting solution was maintained for 24 hours before being used in the processing and fabrication of green samples according to the work of R. Tchouateu et al. and Z. Koadri et al respectively [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe fibers used this work is the by-product derived from the palm leaves (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea), harvested in palm farm neighboring at Dibombari, Littoral-Cameroon. Prior, after collection this biowaste, its defibration was done manually (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). The obtained fibers were treated using 2.5M of NaOH (for 7 hours) to improve the adhesion of the matrix-fiber interface. Because the nature of the surface and the hydrophobic character of natural fibers result in low mechanical qualities for the end-products, it is critical to treat these fibers to improve these capabilities. After the soda treatment, the fibers are saturated in an acidified solution (Acethic Acid), thoroughly rinsed with tap water to remove all residues of NaOH, air-dried for 24 hours, and cut into two distinct lengths (16 and 4 cm).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Composite preparation\u003c/h2\u003e \u003cp\u003eFor unstabilized compressed earth bricks (CEB) were made by uniaxial pressing at 8MPa of the homogeneous mixture of clayey soil and fibers. The water and mass ratio is fixed at 0.3.\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eFor the formulation of stabilized earth bricks (CEBs0), the following process was used: Powdered clayey soil and natural pozzolan were manually mixed. Afterwards, the activating solution was added, and the obtained mortar was further mixed by 5 minutes. Subsequently the different products were obtained by compressing the mixture to 8 MPa. The ratio liquid and solid is fixed at 1 following the Eq.\u0026nbsp;(\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e)\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\frac{alcaline solution}{natural pozzolan}=1$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe production of composite matrices consists by compressing the prismatic form of mixing alkali activated mortar and various proportions of treated fibers from 0 to 0.5 wt.% at 1.5 cm in relation to the total thickness of samples. The specimens were labelled CEBs0.1, CEBs0.2, CEBs0.3, CEBs0.4 and CEBs0.5 (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e ant Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Two sets of compressed blocks forms including cubic (4 \u0026times; 4 \u0026times; 4 cm3) and prismatic (4 \u0026times; 4 \u0026times; 16 cm3), were made using mechanical uniaxial press at 8MPa. The obtained blocks were sealed in plastic bags at room temperature before the curing regime at 7 and 90 days. By the end of the curing, the hardened samples were subjected to various tests.\u003c/p\u003e \u003cp\u003eThe lignocellulosic wt.% composition of treated palm fibers was assessed using Pycnolab laboratories' chemical procedures. The detailed procedure was described by I. Elfaleh et al [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePercentage of basic materials for each type of compressed earth brick.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003esamples\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCEB\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCEBs0\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCEBs0.1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCEBs0.2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCEBs0.3\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eCEBs0.4\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eCEBs0.5\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eClays soil\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e84,9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e84.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e84.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e84.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e84.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGeopolymer binder\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epalm fibers\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0,1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Characterization of raw material and composite structures\u003c/h2\u003e \u003cp\u003eThe different fractions of used clayey soils were evaluated the sedimentation techniques for fine particles according to ASTM D79280s standard[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The workability of the soils under the Atterberg limit was done by determining index plasticity values following ASTM D43180 standard[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The potential crystalline phases within the raw materials and the produced blocks were evaluated through Powder X-ray Diffraction (XRD) techniques through the Brucker-AXS D8 Debye-Scherrer type (Cukα, ƛ.= 1.5418 A) 2Ɵ in range 5\u0026ndash;70\u0026deg;C. The phase\u0026rsquo;s identification was carried out using HighScore Plus software.\u003c/p\u003e \u003cp\u003eFTIR analysis was performed to identify the various functional groups found in these samples. The KBr technique was used to record infrared spectra using a Bruker Vertex 80v spectrometer. This was done with a resolution of 2 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 16 scans of the pellet from each sample. Each pellet was made by combining roughly 1.2 mg of the material with approximately 200 mg of KBr.\u003c/p\u003e \u003cp\u003eThe morphological features of the specimens without and with fiber were observed using a Jeol XFlash 6160 Bruker scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). The samples were coated with a thin layer of gold to make them measurable under the microscope.\u003c/p\u003e \u003cp\u003eThe mechanical properties of crushed earth bricks, including three-point flexural and compressive strengths (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea and b), were tested on wet and dry specimens using a compression test machine from Impact Test, UK with a maximum load capacity of 250 KN. Mean values and standard deviation were calculated using four representative samples for each formulation.\u003c/p\u003e \u003cp\u003ePhysical properties, including water absorption, were assessed on samples of 4 \u0026times; 4 x 4 cm\u003csup\u003e3\u003c/sup\u003e. For the water absorption (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec) and wet strengths tests,7 and 90days aged samples were dried and weighted at room temperature until constant mass before being immersed in water at room temperature for 48 hours. In terms of water absorption, after removing the water sample, the mass of the wet samples was weighed and compared to the mass of the dry samples using the ASTM C642-06 standard [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Characterization of basic materials\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e4\u003c/span\u003ea and Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e4\u003c/span\u003eb display the diffractogram patterns of clay soil (CS) and natural pozzolan (PZ). The diffractogram of clay soil shows that it is essentially composed of kaolinite (PDF-Nr.-000010527), quartz (PDF-Nr.-010741811), goethite (PDF-Nr.-010771060) and microcline (PDF-Nr.-000190926).\u003c/p\u003e \u003cp\u003eAs can been seen from Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e4\u003c/span\u003eb, the natural pozzolan is predominantly made of phases that include: labradorite (PDF-Nr.-010831372), augite (PDF-Nr.-010781392), anorthite (PDF-Nr.-000411481); diopside (PDF-Nr.-010820460) and hematite (PDF-Nr.-000240072).\u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows physical properties of clay soil, principal material used for the manufacture of different compressed earth bricks (CEB). The particle size distribution shown that, clay soil consisted of 0.29% gravel, 74.22% sand, 2.94% silt and 22.54% clay. According to Atterberg, it is a medium-plastic clay because its plasticity index is between 7 and 17. Moreover, the classification of soils according to their nature, based on the particle size distribution of the sample, its plasticity index (11.47) shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, classified the studied clay as type B5 (acceptable clay soil)[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePhysical properties of clay soil (CS)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSample\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003egravel Ф\u0026gt;2 mm\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003esand 2\u0026gt;Ф\u0026gt;0.02 mm\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003esilt 0.02\u0026gt;Ф\u0026gt;0.002 mm\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eclay Ф\u0026lt;0.002 mm\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLiquid limit\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003ePlastic limit\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003ePlasticity index\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003ePlasticity Domain\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e74.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e22.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e32.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e43.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e11.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eMedium Plastic\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Chemical composition of palm fiber\u003c/h2\u003e \u003cp\u003eThe properties of natural fibers, their mechanical capabilities and weak resistances are influenced by their chemical composition. The chemical composition of palm fibers used in this study is mentioned in Table \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Non-treated palm consisted of cellulose (46.8%), hemicellulose (20%) and lignin (30.5%). After cellulose, lignin, which is the second most abundant renewable organic substance on this palm fibers. Generally, the tensile strength and Young\u0026rsquo;s modulus of fibers increase with an increase in cellulose content and, lignin provides plants with water resistance due to its hydrophobicity and contributes to the rigidity and hardness of materials[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. However, plant fibers have certain drawbacks when combined with polymers. The presence of hydroxyl groups in lignocellulose, plant fibers are hydrophilic, making them incompatible with hydrophobic thermoplastics and prone to moisture damage[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. These limitations pose challenges for using plant fibers as polymer reinforcement. To improve adhesion between fibers and the polymer matrix and reduce moisture absorption, surface modifications are typically required. It is the reason of the use of alkaline (NaOH) treatment in this context to enhance fiber-matrix compatibility and improve composite quality[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. As the values mentioned in Table \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, alkaline treatment considerably reduces the percentage of lignin (30.5 to 15.1%) and hemicellulose (20 to 9%). The reason of the weak reduce of cellulose percentage (46.8 to 40) it is that, the alkaline treatment involves reacting the fiber's hydroxyl functions (-OH) of cellulose with acetyl groups (CH\u003csub\u003e3\u003c/sub\u003eCO\u003csup\u003e\u0026minus;\u003c/sup\u003e) to give the fiber a hydrophobic surface[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. The reaction of NaOH with cellulose can be represented as follows:\u003c/p\u003e \u003cp\u003e \u003cem\u003eCellulose\u003c/em\u003e - \u003cem\u003eOH\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eNaOH\u003c/em\u003e \u0026rarr; (\u003cem\u003eCellulose\u003c/em\u003e - \u003cem\u003eO\u003c/em\u003e)\u0026thinsp;+\u0026thinsp;\u003cem\u003eNa\u003c/em\u003e\u003csup\u003e+\u003c/sup\u003e + \u003cem\u003eH\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e\u003cem\u003eO\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eimpurity (3)\u003c/em\u003e\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eChemical characteristics of non-treated and treated palm fibers\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003eConstituents (% weight)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eNon-treated palm fiber\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLignin\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ehemicellulose\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCellulose\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e46.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003etreated palm fiber\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Mechanical characterization of composite materials\u003c/h2\u003e \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e \u003ch2\u003e3.3.1 Dry compressive strength\u003c/h2\u003e \u003cp\u003eThe compressive strength test was performed after 7 days and 90 days of curing. The results obtained from the dry compression test as a function of the alkaline geopolymer binder percentage (0 and 15%) and curing days (7 and 90 days) are summarized in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003ea. when curing time further increased from 7 days to 90 days, a weak decrease in compressive strength was observed for the unstabilized bricks. This decrease is due to the formation of crack in the unstabilized earth brick matrix with curing time. However, the adding of the geopolymer binder (natural pozzolan\u0026thinsp;+\u0026thinsp;alkaline solution) and curing days directly affects the compressive strength performance of compressed earth bricks. With the adding of 15% of the geopolymer binder at 90 days the compressive strength of bricks increases considerably. This resistance increases from 0.68 to 2.5 MPa respectively for bricks containing 0% and 15% at 7 days of curing and from 2.5 to 5.5 MPa for bricks with 15% of geopolymer binder at 90 days. It shows that compressive strength of the earth bricks is improved with the addition of binder and the strength of alkaline geopolymer concrete increases with the curing time.\u003c/p\u003e \u003cp\u003eThe dry compressive strengths of the fiber-free and fiber-stabilized bricks obtained as a function of their content and curing time are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003eb. The dry compressive strength of the material increases with curing time and with the rate of fiber addition up to 0.4%. This increase is due to the geopolymer binders whose bonds develop and strengthen with time, and to the role played by the fibers as a reinforcement taking over the forces transmitted to the clay soil - geopolymer binder matrix. The decrease in strength at 0.5% of fibers would be due to the fact that there are more fiber-fiber contacts since the wettability of the fibers by the matrix has become low[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. In addition, the matrix formed by the fibers would no longer be in sufficient contact with the clay-binder matrix. Optimum dry compressive strength is achieved for an optimal proportion of 0.4% fibers by weight. At this rate, the resistance is 5.5 MPa compared to the fiber brick which is 8.08 MPa. Furthermore, the increase in resistance for all samples from 7 to 90 days is 3 MPa. This identical increase reflects the fact that the curing time did not have an influence on the treated palm fibers but positively influenced the development of the bonds of the geopolymer binder. This was linked to the alteration with time of some minerals phases present in natural pozzolan and clay soil (i.e. hematite, goethite) in alkaline medium allowing the formation of amorphous phase, sodium aluminosilicate such contributing in reinforcement of geopolymer matrix[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e \u003ch2\u003e3.3.2 Wet compressive strength\u003c/h2\u003e \u003cp\u003eFigures\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003ea and b show respectively the results of wet compressive strength tests of bricks aged of 7 and 90 days with the adding of geopolymer binder and the proportions of palm fibers. The unstabilized bricks with geopolymer binder at 7 days of curing present weak wet compressive strength while, those aged 90 days are destroyed in water. This destruction is due to the fact that the capillarity in the fillers (clays and silt) present in the clay soil used is significant what increases water absorption of this material[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Due to the linear swelling and/or shrinkage that occurs in the clay material due to its moderately plastic nature, open pores and cracks are created which increase with time (90 days) and therefore increase the water permeability of the bricks. The capillarity and permeability significant of these unstabilized bricks leads to the destruction of the bonds present which leads to weak wet resistance or even the destruction of these materials. Furthermore, and for the same reasons mentioned in section \u003cspan refid=\"Sec11\" class=\"InternalRef\"\u003e3.3.1\u003c/span\u003e, the adding of the geopolymer binder (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003ea) and treated palm fibers (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003eb) positively affects the wet compressive strength of compressed earth bricks and their stability in humid areas (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec). in addition, a reduction of 75% compared to dry compressive resistance is observed in the case of bricks stabilized with 15% of geopolymer binder, while in the case of stabilized bricks containing palm fibers, this reduction is 65%. The addition of treated palm fibers thus has a real advantage for the water resistance of earth bricks stabilized by an alkaline geopolymer binder. Furthermore the wet strength values of the fibrous composites obtained are significantly higher than that recommended by the standard for construction with earth bricks (\u0026lt;\u0026thinsp;1 MPa) However, optimum wet compressive strength (3.2 MPa) is achieved for an optimal proportion of 0.4% fibers at 90 days.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e \u003ch2\u003e3.3.3 Flexural strength\u003c/h2\u003e \u003cp\u003eThe values of flexural strength of the different samples are reported in Figs.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003ea and b. It is noticed that the flexural values are higher for compressed earth bricks stabilized with alkaline geopolymer binder compared to those obtained without stabilization at 7 and 90 days (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003ea). With regard to CEBs with geopolymer binders, the improvement in their mechanical parameters is attributable to the production of geopolymer gels that bond the particles together, thus making the samples compact and resistant with time[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Furthermore, there is a considerable increase in flexural values with the adding of palm fibers. This resistance ranges from 3.5 MPa for fiber less bricks to 6 MPa for bricks with 0.4% fibers at 90 days. As in the case of compressive strength, the maximum value is obtained with an addition rate of 0.4% fiber. In this case of study where the composites have a fibrous matrix, the flexural strength is a characteristic whose interpretation is related to those of the compressive strength because the reinforcement during the test was placed on the side of the stretched face[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. However, the addition of 0.5% fiber (drop point) to improve the mechanical bending behavior of composites is much more important than the improvement in compressive strength because the fibers participate in the seam of cracks during the bending test.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e \u003ch2\u003e3.3.4 Water absorption\u003c/h2\u003e \u003cp\u003eFigures\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e8\u003c/span\u003ea and b show the results of the water absorption of the synthesized compressed earth bricks. Due to the increase in cracks in unstabilized earth brick over time, CEB aged 90 days and without alkaline geopolymer binder were very vulnerable to water and disintegrated completely (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e8\u003c/span\u003ea). The sample stabilized with 15% of geopolymer had excellent cohesion in water and the water absorption value varies for 3. 2 to 2.6% at 7 and 90 days respectively. This observation of decrease of the water absorption rate is related to the maturation of the geopolymer matrix, which becomes more compact over time[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. In Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e9\u003c/span\u003eb, the water absorption rate for 7-day-old bricks increases with the fiber content, while the water absorption rate decreases for 90-day-old bricks. This is related to the fact that the matrix of 7-day-old materials is not more compact and the fact that, the fibers absorb a very high amount of water, which generates a high mass gain within the composite[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. According to the results obtained, time is a favorable factor for the development of strong bonds within the geopolymerized matrix that ensures good fiber-matrix adhesion.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Mineralogical characterization of composite materials\u003c/h2\u003e \u003cdiv id=\"Sec16\" class=\"Section3\"\u003e \u003ch2\u003e3.4.1 X-Ray Diffraction analysis\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e9\u003c/span\u003e displays the diffractogram patterns of unstabilized compressed earth bricks (CEB), stabilized compressed earth bricks with 15% of geopolymer binder (CEBs0) and stabilized compressed earth brick contain 0.4% of palm fiber (CEBs0.4).The phase identification show that CEB consists the same phase identified in the clay soil: kaolinite (PDF-Nr.-000010527), quartz (PDF-Nr.-010741811), goethite (PDF-Nr.-010771060) and microcline (PDF-Nr.-000190926). CEB being made up only of CS and water, this water did not bring any modification to the mineralogy of CS. Furthermore, the addition of 15% of geopolymer binder (natural pozzolan\u0026thinsp;+\u0026thinsp;alkaline solution) justifies the presence of new phases observed on the CEBs0 diffractogram. These new phases come from natural pozzolan used as the main precursor of geopolymerization reaction and correspond to: anorthite (PDF-Nr.-000411481); diopside (PDF-Nr.-010820460); hematite (PDF-Nr.-000240072). Observing the diffractogram of the sample stabilized with a geopolymer binder and containing 0.4% of palm fiber (CEBs0.4), we see that the addition of treated palm fibers does not cause any modification to the mineralogy of the samples. This reflects their non-deterioration after 90 days of curing. The decrease in the intensity of kaolinite peaks located at 12.32 ◦, and 24.91◦\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\theta\\)\u003c/span\u003e\u003c/span\u003e and the disappearance of goethite peaks located at 21.20◦ and 41.27 ◦\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\theta\\)\u003c/span\u003e\u003c/span\u003e means that, the kaolinite and goethite contained in clay soil dissolves partially in the activating alkaline solutions to contribute to formation of amorphous phase i.e. geopolymer network which plays the role of stabilizer in the matrix within the different composites (CEBs0 and CEBs0.4)[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. In addition, phases such as labradorite (PDF-Nr.-010831372) and augite (PDF-Nr.-010781392), initially present in natural pozzolan are not identified in the composites (CEBs0 and CEBs0.4). This means that alkaline solution, once in contact with precursors dissolves the reactive phases to form the geopolymer network.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section3\"\u003e \u003ch2\u003e3.4.1 FTIR analysis\u003c/h2\u003e \u003cp\u003eThe IR spectra of the composite materials: CEB, CEBs0 and CEBs0.4 are illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e10\u003c/span\u003e. Bands located at 3623 and 3695 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e characterized absorption bond belong to the hydroxyl (O\u0026ndash;H) group of kaolinite[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. The absorption bond present at 3474 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e on all IR spectra is attributed to the hydroxyl group (O\u0026ndash;H) of water molecules[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. The band located at 1622 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (CEB) and 1661 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (CEBs0) on is described to the H-O\u0026ndash;H bond of water molecules[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. The absence of this band on the spectrum of the sample containing 0.4% of palm fiber (CEBs0.4) reflects the sorption capacity of the water molecules of these fibers. This is consistent with the results obtained in the case of the variation in water absorption of the different samples (section \u003cspan refid=\"Sec14\" class=\"InternalRef\"\u003e3.3.4\u003c/span\u003e). The symmetrical stretching vibration bands at 908, 914, 1031and 1083 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e correspond to Si-O-T, (T\u0026thinsp;=\u0026thinsp;Si, Al, Fe)[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. The absorption band at 687 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e characterized the bending vibration mode of Fe-OH of goethite[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. The decrease of this band (Fe-OH) after alkaline activation is due to the alteration of the minerals (kaolinite and goethite) present in CS[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. This analyze corresponds to the observation made in section \u003cspan refid=\"Sec16\" class=\"InternalRef\"\u003e3.4.1\u003c/span\u003e. The stretching vibration absorption bands located at 537 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is attributed to the Fe-O-T (T\u0026thinsp;=\u0026thinsp;Al, Si, Fe), due to the stretching vibration bands of Fe-O[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. After analysis of these spectra, the main aluminosilicate band, located at 1031 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 914 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e on the sample without stabilization (CEB), shifts respectively to 1037 and 908 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e on stabilized brick without fiber (CEBs0) and stabilized with 0.4% of fiber (CEBs0.4) spectra. This change show a restructuring of the aluminosilicate during geopolymerization process, a result of the alteration of phases such as kaolinite and goethite [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. The fact that these bands shift at the same wavenumbers for the stabilized sample (CEBs0) and the stabilized sample containing 0.4% of palm fibers (CEBs0.4) reflects the fact that the treated palm fibers do not affect the geopolymerization process. This observation confirms once again that these fibers do not deteriorate after 90 days of curing. The news bands at 1453 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e on CEBs0 and at 1460 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e on CEBs0.4 spectra are attributable of O\u0026ndash;C\u0026ndash;O bond of natrite resulting from the carbonation reaction resulting between CO\u003csub\u003e2\u003c/sub\u003e atmospheric and the free Na\u003csup\u003e+\u003c/sup\u003e ions[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section3\"\u003e \u003ch2\u003e3.4.2. \u003cb\u003eSEM/EDS analysis\u003c/b\u003e\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e11\u003c/span\u003e shows selected micrographs of bricks without (F0) and with (F3) fibers. These images show the cohesion between the binder and the non-reactive phases of earth, sand, and fibers, forming a compact structure. This compactness demonstrates the effectiveness of the geopolymer binders in bonding the components of the composite earth bricks. The fibers are not observed in the matrix even at high magnification, which shows that the binder used perfectly encapsulates the fibers. This situation shows that the treated fibers act perfectly as a filler in the matrix. The cracks observed are the impacts of the loads received by the material during the compressive test. At the interfaces of the crystalline grains, a layer adheres, and the results of the chemical analyses presented on the extreme right of the micrographs show that these layers do not have the same chemical compositions, thus revealing the heterogeneous nature of the brick. The failure to observe the geopolymer chains is due to the fact that the fraction of geopolymer formed causes the earth particles to adhere on a microscopic scale, and the mortar formed in turn adheres the grains of sand and fibers on a macroscopic scale.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":" \u003cp\u003eThis work focused on the study of the addition of treated palm fibers on the mechanical, mineralogical, and microscopic properties of clay bricks stabilized by a geopolymer binder based on natural pozzolan. First, it has been demonstrated that the alkaline geopolymer binder improves the physic-mechanical properties of clay bricks. Subsequently, the addition of palm fibers has enabled an optimization of these properties without affecting the geopolymerization reaction during which there is formation of the gel that ensures the fiber-matrix adhesion of the composite formed. A study of the mineralogical properties of the 90-day-old matrices showed that the kaolinite and goethite contained in clay soil dissolves partially in the activating alkaline solutions to contribute to formation of amorphous phase and the addition of treated palm fibers to bricks stabilized by an alkaline geopolymer binder does not change the mineralogical composition of the base materials. Furthermore, the optical analysis shows that the binder used perfectly encapsulates the fibers. This situation shows that the treated fibers act perfectly as a filler in the matrix. Thus, this work demonstrates the potential of these composite materials (geopolymerized brick-treated palm fiber) to be used in sustainable and ecological construction applications. However, an additional 0.4% of palm fibers in earth bricks stabilized by the alkaline geopolymer binder based natural pozzolan is recommended for the construction of buildings.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors thank LASOGEMA (IUT-Douala-Cameroon) for extending all the facilities to carry out this research.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRolande Aurelie Tchouateu Kamwa, Sylvain Tome, Joseph Bikoun Mousi\u003c/strong\u003e: Validation, Methodology, Writing - review \u0026amp; editing, Visualization, original draft,\u003cstrong\u003e\u0026nbsp;Rolande Aurelie Tchouateu Kamwa Joseph Bikoun Mousi, sylvain Tome, Juvenal D Neumaleu\u003c/strong\u003e: Conceptualization, Methodology, Investigation, Writing - original draft. \u003cstrong\u003eSylvain Tome\u003c/strong\u003e, \u003cstrong\u003eRolande Aurelie Tchouateu Kamwa, Martine Gerard:\u0026nbsp;\u003c/strong\u003ePXRD, FTIR analysis,\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eValidation, Writing - review \u0026amp; editing, Visualization, \u003cstrong\u003eRolande Aurelie Tchouateu Kamwa, Tome Sylvain, Juvenal D Neumaleu Joseph Bikoun Mousi\u003c/strong\u003e: Methodology, Writing review \u0026amp; editing, original draft: Supervision, Methodology, Resources, \u003cstrong\u003eJacques Etame, Marie-Annie Etoh\u003c/strong\u003e: Resources, Supervision\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003c/strong\u003eThe authors of manuscript did not receive any funding and grants for this work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAll data generated or analyzed during this study are included in this article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompliance with ethical standards\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot Applicable\u003cstrong\u003e\u0026nbsp;\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot Applicable\u003cstrong\u003e\u0026nbsp;\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eOti JE, Kinuthia JM (2020) The Development of Stabilised Clay-Hemp Building Material for Sustainability and Low Carbon Use. 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J Clean Prod 3. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jclepro.2018.07.171\u003c/span\u003e\u003cspan address=\"10.1016/j.jclepro.2018.07.171\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTome S, Annie M, Jacques E, Sanjay E (2019) Improved Reactivity of Volcanic Ash using Municipal Solid Incinerator Fly Ash for Alkali-Activated Cement Synthesis. Waste Biomass Valoriz 0(0):0. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1007/s12649-019-00604-1\u003c/span\u003e\u003cspan address=\"10.1007/s12649-019-00604-1\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"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":"earth brick, alkaline stabilization, treated palm fibers, properties","lastPublishedDoi":"10.21203/rs.3.rs-4200988/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4200988/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe aim of this work is to study the influence of the palm fibers treated with soda hydroxide solution, on the properties of the compressed earth bricks stabilized with 15% of natural pozzolana based alkaline geopolymer binder. To achieve this objective, mortars composed of treated fibers at different levels (0.1, 0.2, 0.3, 0.4 and 0.5%) for a length of 4 and 16 cm, have been developed. These different mortars with those without fibers were subjected to mechanical (dry compression, wet compression, and flexion), physical (water absorption), mineralogical (XRD, FTIR) and microstructural (SEM/EDX) characterizations after 7 and 90 days. The results obtained show that, in general the addition of fibers improves the mechanical and physical properties of compressed earth bricks stabilized with 15% of alkali-geopolymer binder. In addition, the adding of treated palm fibers does not have an influence on the mineralogical composition of the composite bricks. The observation of the diffractograms of FTIR analysis shows that these fibers have a capacity to sorption water molecules. Furthermore, the optical analysis shows that the binder used perfectly encapsulates the fibers. This situation shows that the treated fibers act perfectly as a filler in the matrix. The maximum dry compressive strength and flexural strength values are obtained with the addition of 0.4% fibers at 90 days and are 8.08 and 5.8 MPa respectively. Furthermore, an additional of 0.4% of palm fibers in earth bricks stabilized by the alkaline geopolymer binder based natural pozzolan is recommended for the construction of buildings.\u003c/p\u003e","manuscriptTitle":"Effect of treated palm fibers on the mechanical properties of compressed earth bricks stabilized by geopolymer binder based natural pozzolan","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-22 04:35:55","doi":"10.21203/rs.3.rs-4200988/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":"4dce7f0b-1979-491c-87b4-53116082c658","owner":[],"postedDate":"April 22nd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-04-22T04:35:56+00:00","versionOfRecord":[],"versionCreatedAt":"2024-04-22 04:35:55","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4200988","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4200988","identity":"rs-4200988","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}