Improving the adobe structures by bio friendly materials

Improving the adobe structures by bio friendly materials | 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 Improving the adobe structures by bio friendly materials Mehdi Savary, Soheyl Sazedj, Jorge Filipe Ganhão da Cruz Pinto, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6939709/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 Adobe, a sustainable, inexpensive, and environmentally friendly material, is used in approximately 30% of the world's housing and constitutes 10% of UNESCO's registered heritage sites. However, the long-standing challenge of strengthening clay materials and adobe structures has led to the exploration of various techniques, including the addition of strengthening agents. This research investigates the potential of climate-compatible biopolymers as an alternative to traditional soil stabilizers, aiming to develop an eco-friendlier approach to reinforcing earth and adobe structures. Specifically, we explore novel biological technologies for strengthening clay and adobe, comparing their performance against traditional stabilizers. Our study involves creating various sample combinations using traditional additives like cement, lime, and sand, alongside the bio-friendly material chitosan, at different percentages. These samples undergo laboratory testing to provide a robust and scientific comparison of their properties. Notably, the production of these samples requires minimal energy, suggesting a potentially low embodied energy and reduced greenhouse gas emissions for the final product. Preliminary mechanical tests, including bending and compressive strength analyses, indicate significant improvements in samples incorporating chitosan. Soil treatment chitosan biopolymer green technology Adobe architecture Figures Figure 1 Figure 2 Figure 3 Figure 4 Statement of the problem Adobe, a sustainable, inexpensive, and environmentally friendly material, is used in approximately 30% of the world's housing [1] and constitutes 10% of UNESCO's registered heritage sites [2]. These structures are highly vulnerable to earthquake and other damaging agents, including moisture. Therefore, special attention must be given to preserving such historical structures and retrofitting of existing buildings in use, which can lead to the survival of such historically valuable structures and to make affordable rural housing available. Some of the advantages of using adobe for construction are low environmental pollution, affordability, thermal storage. Adobe production requires only 1% of the energy needed to produce Portland bricks or cements. Another advantage of adobe is the rapid drying of the mortar [3]. Other advantages include easy and inexpensive production, having acoustic properties, and since it is made of soil it can be returned to nature and is recyclable [4]. Strengthening adobe and adobe structures dates back as early as the construction of these buildings. Some of the organic materials used in strengthening the adobe and adobe structures are animal blood, animal dung, animal fat, straw and animal fibers such as goat hair [5][6][7]. Minerals that are used extensively include sand, plaster, limestone, and cement [8]. Of course, the use of these materials is entirely experimental and has achieved satisfactory results. With the advancement of science and technology, especially in the past few decades, the performance of these materials has been scientifically investigated and experimented. Novel methods for strengthening adobe have been proposed, for example, developing and using synthetic nano materials to optimize the adobe [9][10][11], such as composites [12], and synthetic fibers, as polypropylene [13]. Concerning the use of modern materials, it has been stated in the tenth article of the 1962 Charter, Venice that: "In cases where it is acknowledged that previous techniques are unsuitable, retrofitting operations can be carried out using the most modern tools and techniques. It is obvious that the merits of these devices and techniques must be established through science and experience” [1]. Earthquake is one of the factors that has caused the destruction and erosion of adobe masonry throughout history. It creates vibrations on the body of the structure and due to these vibrations, the walls move and bow. Extremely 4 heavy adobe buildings with low resistance and fragile behaviors have gone through significant damage and have taken thousands of lives. According to reports on the January 2001 El Salvador earthquake, about 200,000 adobe structures were damaged and led to 1100 casualties [14]. The behavior of adobe walls during earthquakes is subject to various conditions. The common pattern of the destruction of adobe walls during an earthquake begins with the formation of vertical cracks in the place where the walls and the ceiling meet and expands rapidly until the walls are separated from the ceiling, after this separation, the front wall collapses and then the ceiling falls. Considering this structural behaviour, soil can be strengthened by mechanical, physical, and chemical means [15]. State of the art of biopolymer Biopolymers are organic polymers synthesized by biological organisms and formed through the bonding of monomer units. The application of biopolymers in geotechnical engineering is not considered entirely novel, as organic polymers such as natural bitumen has been used in ancient civilizations. In ancient China, for instance, a slurry with high strength and durability was produced by combining a type of sticky rice with sugarcane, lime, and river sand [16]. Among the three most common types of biopolymers—polynucleotides (such as RNA and DNA), polypeptides (composed of amino acids), and polysaccharides—polysaccharides have the most widespread use in civil engineering projects [17]. Polysaccharides are carbohydrate-based polymer chains formed by the linkage of monosaccharide units. These compounds are abundant in nature and serve as structural and skeletal components in living organisms (e.g., cellulose and pectin in plants, and chitin in animals), as well as energy storage materials (e.g., starch in plants and glycogen in animals). The properties of biopolymers have led to their extensive use in the food industry, agriculture, and therapeutic applications [18]. Biopolymers in Geotechnical Engineering When mixed with soil, biopolymers act as a binding agent, leading to improved soil strength, enhanced erosion resistance, and reduced permeability [19]. The use of biopolymers for soil improvement offers several advantages over other modern ground improvement techniques, such as microbial injection. For instance, this method does not require the injection of microbes and nutrients, nor time for microbial cultivation and precipitation processes. Moreover, it can be effectively applied to fine-grained soils, including clayey soils. In addition, biopolymers are readily found in nature, and many of them are known to be non-toxic and even edible. As such, they can be considered environmentally friendly materials for soil improvement. In recent years, several polysaccharide-based biopolymers have been evaluated for use in geotechnical engineering, and the properties of some of these are presented in Table 1 . Chitosan Chitosan is a biopolymer derived from chitin, which is primarily obtained from the hard exoskeletons of marine organisms. To extract chitin, the shells or carapaces of marine animals are first separated and subjected to deproteinization using a 5% (by weight) sodium hydroxide solution. This is followed by demineralization in a 2% (by weight) hydrochloric acid solution to remove the mineral content. If the resulting product has a degree of deacetylation less than 50%, the substance is referred to as chitin. However, if the degree of deacetylation exceeds 50%, the resulting material is known as chitosan [24]. The process for producing chitin and some of its derivatives from the hard exoskeletons of marine animals is illustrated in Fig. 1 . Chitosan has two major advantages over chitin. First, chitin is only soluble in toxic solvents such as lithium chloride and dimethyl acetamide, whereas chitosan is soluble in mild acidic solutions, such as acetic acid. The second advantage is that chitosan contains a greater number of free amino groups compared to chitin. In addition to these benefits, it is important to note that chitin rarely exists in pure form; rather, it is typically found in combination with substances such as calcium carbonate, proteins, and other organic materials. Chitosan, as a biocompatible and biodegradable biopolymer, has been widely applied in various fields, including the food industry, agriculture, cosmetics, and medicine (Table 2 ). Table 2 Application of chitosan in various fields [26–27]. Application area Chemical composition Cosmetics Maintaining skin moisture Acne treatment Improving hair softness Reducing static electricity in hair Oral and dental care (toothpaste, chewing gum) Medicine Surgical suture Dental implants Artificial skin Bone reconstruction Lens manufacturing in ophthalmology Time-controlled drug release in the human body Food industry Cholesterol reducer Preservatives Thickeners and stabilizers for sauces Antibacterial agents Coating for fruits Applications of Chitosan in Civil Engineering Chitosan has been utilized in a variety of applications in the field of civil engineering. Biopolymers such as xanthan gum and chitosan are widely used as viscosity-modifying additives in cement-based materials. The modification of cementitious material properties is also possible specially through nanotechnology, including the production of nanoparticles such as nano chitosan and nanocellulose. Although the use of chitosan in high-performance superplasticizers offers structural and environmental benefits, but achieving the desired properties requires chemical modification of chitosan’s molecular structure. This, in turn, necessitates the development of an efficient and cost-effective method for its chemical modification. Recent studies demonstrate the benefits of chitosan in enhancing the compressive and tensile strength of concrete [28]. Chitosan delays the hydration of cement, thereby extending the initial setting time of concrete, and functions effectively as a plasticizer. Moreover, chitosan has been widely used in the treatment of industrial wastewater. Chitin and chitosan have shown high efficiency in treating effluents from oil refineries [29]. Chitosan has also been employed to remove heavy metals from water and soil. It is capable of disinfecting groundwater contaminated with copper and phosphorus ions. Additionally, sand particles coated with chitosan have been used for the purification of contaminated groundwater [30]. Soil Classification Tests Soil classification tests were conducted in accordance with ASTM standards and with reference to the Eurocode 7 (EN 1997-2) guidelines for geotechnical investigations and testing. Given the fine-grained nature of most of the soil, the Particle Size Distribution Test was carried out in two stages. In the first stage, a sieve analysis was performed following ASTM D421-85, and in the second stage, a hydrometer analysis was conducted according to ASTM D422-63. These procedures ensured accurate grain size classification in compliance with both American and European geotechnical standards. Atterberg Limits Test Following the grain size distribution test, the Atterberg limits of the soil were determined to evaluate its consistency and plasticity. Accordingly, the liquid limit (LL) and plastic limit (PL) tests were conducted on the portion of soil passing through Sieve No. 40, in accordance with ASTM D4318-00. These procedures were also aligned with the recommendations of Eurocode 7 – Geotechnical Design, Part 2: Ground Investigation and Testing (EN 1997-2), which emphasizes the determination of index properties for soil classification. The results of these tests are presented in Table 3 . The compressive strength test Compressive strength tests were conducted on adobe specimens in accordance with ASTM C349 standards. Each specimen was prepared as a 50 × 50 × 50 mm cube using fine-grained clay. Additionally, the testing procedures were aligned with the guidelines of Eurocode 6 – Design of Masonry Structures (EN 1996-1-1) and its related provisions for material characterization, ensuring compliance with both American and European standards for masonry and earthen materials. The initial phase of the study investigated the inclusion of various fibers such as straw, rice husk, and other polymers. Among these, only straw showed promising results and was retained for further evaluation. A total of 18 different adobe compositions were tested, incorporating varying proportions of clay, cement, lime, straw, and chitosan. These compositions were produced in multiple shapes and sizes, and for each composition, five or more specimens were fabricated to ensure result reliability. Based on the performance outcomes, five optimized mixtures were selected for detailed compressive strength testing. The final five compositions tested for compressive strength were as follows: Simple (Control): Clay only Chitosan 0.2: Clay + 0.2% chitosan (no other additives) Chitosan 0.4: Clay + 0.4% chitosan (no other additives) Chitosan Type 1: Clay + 0.2% chitosan + 1.5% lime + 1.5% cement Chitosan Type 2: Clay + 0.2% chitosan + 2.5% lime + 2.5% cement Force–time curves were generated for each sample, and their maximum compressive loads were recorded as follows: Simple: 16.06 KN Chitosan 0.2: 12.74 KN Chitosan 0.4: 6.75 KN Chitosan Type 1: 35.46 KN Chitosan Type 2: 21.60 KN According to European Standards, a minimum compressive strength of 5 N/mm² (12.5 KN) is required for construction materials, while EC5 (masonry structures) recommends at least 10 N/mm² (25 KN). Based on these criteria, only the Chitosan Type 1 sample met the EC5 threshold, while Chitosan Type 2, Chitosan 0.2, and the control sample met the basic European standard. Chitosan 0.4 failed to meet either requirement. These results highlight the substantial improvement in compressive strength provided by chitosan, particularly when combined with lime and cement. These findings clearly demonstrate that the integration of small amounts of chitosan with mineral stabilizers can substantially enhance the mechanical strength of traditional clay-based adobe, potentially making it suitable for structural use in sustainable construction. Analysis of bending Strength Results of Adobe Samples The bending (flexural) strength test was conducted in accordance with ASTM C348, which specifies procedures for testing hydraulic-cement mortars. All specimens were prepared with dimensions of 4 × 4 × 16 cm³ using fine-grained clay soil. In line with European practice, the testing procedure also adhered to the principles outlined in Eurocode 6 – Design of Masonry Structures (EN 1996-1-1) and the associated standards for material testing and characterization. Five types of samples were examined, each incorporating different stabilizing additives or treatment methods. Simple: Made solely from clay, used as reference. Chitosan 0.2: Clay blended with 0.2% chitosan biopolymer. Chitosan 0.4: Contained 0.4% chitosan biopolymer. Chitosan Type 1: Included 0.2% chitosan, 1.5% lime, and 1.5% cement. Chitosan Type 2: Included 0.2% chitosan, 2.5% lime, and 2.5% cement. According to the Force vs. Time graph, the peak bending forces recorded were: Simple: 1.59 KN Chitosan 0.2: 0.95 KN Chitosan 0.4: 0.99 KN Chitosan Type 1: 2.11 KN Chitosan Type 2: 1.63 KN Among the tested samples, Chitosan Type 1 exhibited the highest bending strength, demonstrating the most effective enhancement when combining chitosan with moderate lime and cement content. Although Chitosan Type 2 had a higher percentage of lime and cement, its performance was slightly lower, possibly due to factors like increased porosity or uneven distribution. The results confirm that even small amounts of chitosan can improve the mechanical properties of adobe, with optimal results achieved through balanced combinations with mineral additives. Mechanical Evaluation of Adobe Walls Reinforced with Chitosan, Lime, and Cement (Software-Based Simulation) Five adobe wall types were digitally modelled and analysed using AI-based structural simulation software. Each wall was formulated using different combinations of fine-grained clay, chitosan, lime, and cement, with dimensions of 4 meters in length, 3 meters in height, and 0.5 meters in thickness. The mechanical evaluation, including compressive strength and flexural behaviour, was conducted computationally and not through physical laboratory testing. Simulation results indicated that the Simple wall (clay only) failed to meet minimum strength criteria, while all chitosan-reinforced variants surpassed both compressive and flexural performance thresholds. Among them, the Chitosan Type 2 wall demonstrated the highest compressive strength at 48.03 KN, making it the most suitable for load-bearing applications. On the other hand, the Chitosan Type 1 wall showed superior flexural resistance, highlighting its potential for withstanding lateral forces, such as those from wind or seismic activity. Notably, the Chitosan 0.4 wall containing no added cement or lime achieved a favourable balance between structural performance and environmental sustainability. These findings suggest that even small additions of the biopolymer chitosan, particularly when used in combination with mineral stabilizers, can significantly improve the structural integrity of traditional adobe constructions. Table 4 Summary of Structural and Practical Performance of Adobe Wall Types Criteria Best Performing Wall Type Compressive Strength Chitosan Type 2 Flexural Resistance Chitosan Type 1 Cost-Effectiveness Chitosan 0.4 Sustainability Chitosan 0.2 / Chitosan 0.4 (less cement) Not Recommended Simple (Control) Conclusion This research demonstrates the significant potential of bio-friendly materials, specifically chitosan, as effective stabilizers and strength enhancers for traditional adobe structures. The experimental results clearly highlight that the incorporation of chitosan, particularly in combination with lime and cement, substantially improves both compressive and flexural strengths of adobe constructions. Among the tested compositions, Chitosan Type 2 showed the highest compressive strength, making it ideal for load-bearing applications, while Chitosan Type 1 provided superior flexural resistance, enhancing resilience to seismic and lateral forces. Moreover, the use of chitosan alone, even at minimal concentrations, notably increased mechanical properties, proving its viability as an eco-friendly stabilizer. Given its biodegradability, non-toxicity, and minimal energy consumption during production, chitosan stands out as a sustainable alternative to traditional stabilizing materials. Future research should explore optimizing the proportions and methods of incorporating chitosan into larger-scale adobe structures, potentially paving the way for broader application in sustainable, resilient, and environmentally responsible construction practices. Declarations Funding: This research was supported by a doctoral scholarship from the Fundação para a Ciência e a Tecnologia (FCT), Portugal [Grant Number: https://doi.org/10.54499/2023.01551.BD. Competing Interests: The authors have no conflicts of interest to declare that are relevant to the content of this article. References K. Behramani, S.V.S. Moghadam. (2012). 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Progress in Polymer Science, 8(4), 373–468. K. Adibkia, M.R. Siahi Shadbad, A. Nokhodchi, A. Javadzedeh, M. Barzegar-Jalali, J. Barar, G. Mohammadi, Y. Omidi. (2007). Piroxicam nanoparticles for ocular delivery: Physicochemical characterization and implementation in endotoxin-induced uveitis. Journal of Drug Targeting, 15(6), 407–416. G.C. Barrere, C.E. Barber, M.J. Daniels. (1986). Molecular cloning of genes involved in the production of the extracellular polysaccharide xanthan by Xanthomonas campestris pv. campestris. International Journal of Biological Macromolecules, 8, 372–374. Y.J. Chang, S. Lee, M.A. Yoo, H.G. Lee. (2006). Structural and biological characterization of sulfated-derivatized oat beta-glucan. Journal of Agricultural and Food Chemistry, 54(11), 3815–3818. R. Bazargan Lari. (2011). Preparation of chitosan from shrimp shells for the adsorption of heavy metal ions from aqueous solutions using chitosan and hydroxyapatite (Ph.D. dissertation, Shiraz University, Department of Materials Engineering). E.B. Denkbas, R.M. Ottenbrite. (2006). Perspectives on: Chitosan drug delivery systems based on their geometries. Journal of Bioactive and Compatible Polymers, 21(4), 351–368. M. Rinaudo. (2006). Chitin and chitosan: Properties and applications. Progress in Polymer Science, 31(7), 603–632. M. Kumar. (2000). A review of chitin and chitosan applications. Reactive and Functional Polymers, 46(1), 1–27. U.T. Bezerra, R.M. Ferreira, J.P. Castro-Gomes. (2011). The effect of latex and chitosan biopolymer on concrete properties and performance. Key Engineering Materials, 466, 37–46. M.A. Ashraf, M.J. Maah, I. Yusoff. (2012). Polyvinyl acetate (PVA) as fill material for land reclamation. Chiang Mai Journal of Science, 39(4), 693–711. M.W. Wan, I.G. Petrisor, H.T. Lai, D. Kim, T.F. Yen. (2004). Copper adsorption through chitosan immobilized on sand to demonstrate the feasibility for in situ soil decontamination. Carbohydrate Polymers, 55(3), 249–254. Tables Tables 1 and 3 are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files Tables.docx 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. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6939709","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":488400019,"identity":"867dff06-e10b-4d2a-81c3-878f858f70e6","order_by":0,"name":"Mehdi 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06:03:41","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":506044,"visible":true,"origin":"","legend":"","description":"","filename":"Tables.docx","url":"https://assets-eu.researchsquare.com/files/rs-6939709/v1/644029fa4238c3ad8bc296ef.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Improving the adobe structures by bio friendly materials","fulltext":[{"header":"Statement of the problem","content":"\u003cp\u003e\u003c/p\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eAdobe, a sustainable, inexpensive, and environmentally friendly material, is used in approximately 30% of the world's housing [1] and constitutes 10% of UNESCO's registered heritage sites [2].\u003c/p\u003e\u003cp\u003eThese structures are highly vulnerable to earthquake and other damaging agents, including moisture. Therefore, special attention must be given to preserving such historical structures and retrofitting of existing buildings in use, which can lead to the survival of such historically valuable structures and to make affordable rural housing available.\u003c/p\u003e\u003cp\u003eSome of the advantages of using adobe for construction are low environmental pollution, affordability, thermal storage. Adobe production requires only 1% of the energy needed to produce Portland bricks or cements. Another advantage of adobe is the rapid drying of the mortar [3]. Other advantages include easy and inexpensive production, having acoustic properties, and since it is made of soil it can be returned to nature and is recyclable [4]. Strengthening adobe and adobe structures dates back as early as the construction of these buildings. Some of the organic materials used in strengthening the adobe and adobe structures are animal blood, animal dung, animal fat, straw and animal fibers such as goat hair [5][6][7]. Minerals that are used extensively include sand, plaster, limestone, and cement [8].\u003c/p\u003e\u003cp\u003eOf course, the use of these materials is entirely experimental and has achieved satisfactory results. With the advancement of science and technology, especially in the past few decades, the performance of these materials has been scientifically investigated and experimented. Novel methods for strengthening adobe have been proposed, for example, developing and using synthetic nano materials to optimize the adobe [9][10][11], such as composites [12], and synthetic fibers, as polypropylene [13]. Concerning the use of modern materials, it has been stated in the tenth article of the 1962 Charter, Venice that: \"In cases where it is acknowledged that previous techniques are unsuitable, retrofitting operations can be carried out using the most modern tools and techniques. It is obvious that the merits of these devices and techniques must be established through science and experience” [1].\u003c/p\u003e\u003cp\u003eEarthquake is one of the factors that has caused the destruction and erosion of adobe masonry throughout history. It creates vibrations on the body of the structure and due to these vibrations, the walls move and bow. Extremely 4 heavy adobe buildings with low resistance and fragile behaviors have gone through significant damage and have taken thousands of lives. According to reports on the January 2001 El Salvador earthquake, about 200,000 adobe structures were damaged and led to 1100 casualties [14]. The behavior of adobe walls during earthquakes is subject to various conditions. The common pattern of the destruction of adobe walls during an earthquake begins with the formation of vertical cracks in the place where the walls and the ceiling meet and expands rapidly until the walls are separated from the ceiling, after this separation, the front wall collapses and then the ceiling falls. Considering this structural behaviour, soil can be strengthened by mechanical, physical, and chemical means [15].\u003c/p\u003e\u003cp\u003e\u003cb\u003eState of the art of biopolymer\u003c/b\u003e\u003c/p\u003e\u003cp\u003eBiopolymers are organic polymers synthesized by biological organisms and formed through the bonding of monomer units. The application of biopolymers in geotechnical engineering is not considered entirely novel, as organic polymers such as natural bitumen has been used in ancient civilizations. In ancient China, for instance, a slurry with high strength and durability was produced by combining a type of sticky rice with sugarcane, lime, and river sand [16].\u003c/p\u003e\u003cp\u003eAmong the three most common types of biopolymers—polynucleotides (such as RNA and DNA), polypeptides (composed of amino acids), and polysaccharides—polysaccharides have the most widespread use in civil engineering projects [17].\u003c/p\u003e\u003cp\u003ePolysaccharides are carbohydrate-based polymer chains formed by the linkage of monosaccharide units. These compounds are abundant in nature and serve as structural and skeletal components in living organisms (e.g., cellulose and pectin in plants, and chitin in animals), as well as energy storage materials (e.g., starch in plants and glycogen in animals). The properties of biopolymers have led to their extensive use in the food industry, agriculture, and therapeutic applications [18].\u003c/p\u003e\u003c/div\u003e"},{"header":"Biopolymers in Geotechnical Engineering","content":"\u003cp\u003eWhen mixed with soil, biopolymers act as a binding agent, leading to improved soil strength, enhanced erosion resistance, and reduced permeability [19]. The use of biopolymers for soil improvement offers several advantages over other modern ground improvement techniques, such as microbial injection. For instance, this method does not require the injection of microbes and nutrients, nor time for microbial cultivation and precipitation processes. Moreover, it can be effectively applied to fine-grained soils, including clayey soils.\u003c/p\u003e\u003cp\u003eIn addition, biopolymers are readily found in nature, and many of them are known to be non-toxic and even edible. As such, they can be considered environmentally friendly materials for soil improvement. In recent years, several polysaccharide-based biopolymers have been evaluated for use in geotechnical engineering, and the properties of some of these are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cb\u003eChitosan\u003c/b\u003e\u003c/p\u003e\u003cp\u003eChitosan is a biopolymer derived from chitin, which is primarily obtained from the hard exoskeletons of marine organisms. To extract chitin, the shells or carapaces of marine animals are first separated and subjected to deproteinization using a 5% (by weight) sodium hydroxide solution. This is followed by demineralization in a 2% (by weight) hydrochloric acid solution to remove the mineral content. If the resulting product has a degree of deacetylation less than 50%, the substance is referred to as chitin. However, if the degree of deacetylation exceeds 50%, the resulting material is known as chitosan [24].\u003c/p\u003e\u003cp\u003eThe process for producing chitin and some of its derivatives from the hard exoskeletons of marine animals is illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003eChitosan has two major advantages over chitin. First, chitin is only soluble in toxic solvents such as lithium chloride and dimethyl acetamide, whereas chitosan is soluble in mild acidic solutions, such as acetic acid. The second advantage is that chitosan contains a greater number of free amino groups compared to chitin.\u003c/p\u003e\u003cp\u003eIn addition to these benefits, it is important to note that chitin rarely exists in pure form; rather, it is typically found in combination with substances such as calcium carbonate, proteins, and other organic materials.\u003c/p\u003e\u003cp\u003eChitosan, as a biocompatible and biodegradable biopolymer, has been widely applied in various fields, including the food industry, agriculture, cosmetics, and medicine (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\u003cdiv class=\"gridtable\"\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\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\u003eApplication of chitosan in various fields [26–27].\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eApplication area\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eChemical composition\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCosmetics\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMaintaining skin moisture\u003c/p\u003e\u003cp\u003eAcne treatment\u003c/p\u003e\u003cp\u003eImproving hair softness\u003c/p\u003e\u003cp\u003eReducing static electricity in hair\u003c/p\u003e\u003cp\u003eOral and dental care (toothpaste, chewing gum)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMedicine\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSurgical suture\u003c/p\u003e\u003cp\u003eDental implants\u003c/p\u003e\u003cp\u003eArtificial skin\u003c/p\u003e\u003cp\u003eBone reconstruction\u003c/p\u003e\u003cp\u003eLens manufacturing in ophthalmology\u003c/p\u003e\u003cp\u003eTime-controlled drug release in the human body\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFood industry\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCholesterol reducer\u003c/p\u003e\u003cp\u003ePreservatives\u003c/p\u003e\u003cp\u003eThickeners and stabilizers for sauces\u003c/p\u003e\u003cp\u003eAntibacterial agents\u003c/p\u003e\u003cp\u003eCoating for fruits\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e\u003cp\u003e\u003cb\u003eApplications of Chitosan in Civil Engineering\u003c/b\u003e\u003c/p\u003e\u003cp\u003eChitosan has been utilized in a variety of applications in the field of civil engineering. Biopolymers such as xanthan gum and chitosan are widely used as viscosity-modifying additives in cement-based materials. The modification of cementitious material properties is also possible specially through nanotechnology, including the production of nanoparticles such as nano chitosan and nanocellulose.\u003c/p\u003e\u003cp\u003eAlthough the use of chitosan in high-performance superplasticizers offers structural and environmental benefits, but achieving the desired properties requires chemical modification of chitosan’s molecular structure. This, in turn, necessitates the development of an efficient and cost-effective method for its chemical modification. Recent studies demonstrate the benefits of chitosan in enhancing the compressive and tensile strength of concrete [28].\u003c/p\u003e\u003cp\u003eChitosan delays the hydration of cement, thereby extending the initial setting time of concrete, and functions effectively as a plasticizer. Moreover, chitosan has been widely used in the treatment of industrial wastewater. Chitin and chitosan have shown high efficiency in treating effluents from oil refineries [29]. Chitosan has also been employed to remove heavy metals from water and soil. It is capable of disinfecting groundwater contaminated with copper and phosphorus ions. Additionally, sand particles coated with chitosan have been used for the purification of contaminated groundwater [30].\u003c/p\u003e\u003cp\u003e\u003cb\u003eSoil Classification Tests\u003c/b\u003e\u003c/p\u003e\u003cp\u003eSoil classification tests were conducted in accordance with ASTM standards and with reference to the Eurocode 7 (EN 1997-2) guidelines for geotechnical investigations and testing.\u003c/p\u003e\u003cp\u003eGiven the fine-grained nature of most of the soil, the Particle Size Distribution Test was carried out in two stages. In the first stage, a sieve analysis was performed following ASTM D421-85, and in the second stage, a hydrometer analysis was conducted according to ASTM D422-63. These procedures ensured accurate grain size classification in compliance with both American and European geotechnical standards.\u003c/p\u003e\u003cp\u003e\u003cb\u003eAtterberg Limits Test\u003c/b\u003e\u003c/p\u003e\u003cp\u003eFollowing the grain size distribution test, the Atterberg limits of the soil were determined to evaluate its consistency and plasticity. Accordingly, the liquid limit (LL) and plastic limit (PL) tests were conducted on the portion of soil passing through Sieve No. 40, in accordance with ASTM D4318-00. These procedures were also aligned with the recommendations of Eurocode 7 – Geotechnical Design, Part 2: Ground Investigation and Testing (EN 1997-2), which emphasizes the determination of index properties for soil classification. The results of these tests are presented in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cb\u003eThe compressive strength test\u003c/b\u003e\u003c/p\u003e\u003cp\u003eCompressive strength tests were conducted on adobe specimens in accordance with ASTM C349 standards. Each specimen was prepared as a 50 × 50 × 50 mm cube using fine-grained clay. Additionally, the testing procedures were aligned with the guidelines of Eurocode 6 – Design of Masonry Structures (EN 1996-1-1) and its related provisions for material characterization, ensuring compliance with both American and European standards for masonry and earthen materials.\u003c/p\u003e\u003cp\u003eThe initial phase of the study investigated the inclusion of various fibers such as straw, rice husk, and other polymers. Among these, only straw showed promising results and was retained for further evaluation. A total of 18 different adobe compositions were tested, incorporating varying proportions of clay, cement, lime, straw, and chitosan. These compositions were produced in multiple shapes and sizes, and for each composition, five or more specimens were fabricated to ensure result reliability. Based on the performance outcomes, five optimized mixtures were selected for detailed compressive strength testing.\u003c/p\u003e\u003cp\u003eThe final five compositions tested for compressive strength were as follows:\u003c/p\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eSimple (Control): Clay only\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eChitosan 0.2: Clay + 0.2% chitosan (no other additives)\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eChitosan 0.4: Clay + 0.4% chitosan (no other additives)\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eChitosan Type 1: Clay + 0.2% chitosan + 1.5% lime + 1.5% cement\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eChitosan Type 2: Clay + 0.2% chitosan + 2.5% lime + 2.5% cement\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003cp\u003eForce–time curves were generated for each sample, and their maximum compressive loads were recorded as follows:\u003c/p\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eSimple: 16.06 KN\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eChitosan 0.2: 12.74 KN\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eChitosan 0.4: 6.75 KN\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eChitosan Type 1: 35.46 KN\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eChitosan Type 2: 21.60 KN\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003cp\u003eAccording to European Standards, a minimum compressive strength of 5 N/mm² (12.5 KN) is required for construction materials, while EC5 (masonry structures) recommends at least 10 N/mm² (25 KN). Based on these criteria, only the Chitosan Type 1 sample met the EC5 threshold, while Chitosan Type 2, Chitosan 0.2, and the control sample met the basic European standard. Chitosan 0.4 failed to meet either requirement.\u003c/p\u003e\u003cp\u003eThese results highlight the substantial improvement in compressive strength provided by chitosan, particularly when combined with lime and cement.\u003c/p\u003e\u003cp\u003eThese findings clearly demonstrate that the integration of small amounts of chitosan with mineral stabilizers can substantially enhance the mechanical strength of traditional clay-based adobe, potentially making it suitable for structural use in sustainable construction.\u003c/p\u003e\u003cp\u003e\u003cb\u003eAnalysis of bending Strength Results of Adobe Samples\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe bending (flexural) strength test was conducted in accordance with ASTM C348, which specifies procedures for testing hydraulic-cement mortars. All specimens were prepared with dimensions of 4 × 4 × 16 cm³ using fine-grained clay soil. In line with European practice, the testing procedure also adhered to the principles outlined in Eurocode 6 – Design of Masonry Structures (EN 1996-1-1) and the associated standards for material testing and characterization. Five types of samples were examined, each incorporating different stabilizing additives or treatment methods.\u003c/p\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eSimple: Made solely from clay, used as reference.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eChitosan 0.2: Clay blended with 0.2% chitosan biopolymer.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eChitosan 0.4: Contained 0.4% chitosan biopolymer.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eChitosan Type 1: Included 0.2% chitosan, 1.5% lime, and 1.5% cement.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eChitosan Type 2: Included 0.2% chitosan, 2.5% lime, and 2.5% cement.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003cp\u003eAccording to the Force vs. Time graph, the peak bending forces recorded were:\u003c/p\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eSimple: 1.59 KN\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eChitosan 0.2: 0.95 KN\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eChitosan 0.4: 0.99 KN\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eChitosan Type 1: 2.11 KN\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eChitosan Type 2: 1.63 KN\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003cp\u003eAmong the tested samples, Chitosan Type 1 exhibited the highest bending strength, demonstrating the most effective enhancement when combining chitosan with moderate lime and cement content.\u003c/p\u003e\u003cp\u003eAlthough Chitosan Type 2 had a higher percentage of lime and cement, its performance was slightly lower, possibly due to factors like increased porosity or uneven distribution.\u003c/p\u003e\u003cp\u003eThe results confirm that even small amounts of chitosan can improve the mechanical properties of adobe, with optimal results achieved through balanced combinations with mineral additives.\u003c/p\u003e\u003cp\u003e\u003cb\u003eMechanical Evaluation of Adobe Walls Reinforced with Chitosan, Lime, and Cement\u003c/b\u003e \u003cb\u003e(Software-Based Simulation)\u003c/b\u003e\u003c/p\u003e\u003cp\u003eFive adobe wall types were digitally modelled and analysed using AI-based structural simulation software. Each wall was formulated using different combinations of fine-grained clay, chitosan, lime, and cement, with dimensions of 4 meters in length, 3 meters in height, and 0.5 meters in thickness. The mechanical evaluation, including compressive strength and flexural behaviour, was conducted computationally and not through physical laboratory testing.\u003c/p\u003e\u003cp\u003eSimulation results indicated that the Simple wall (clay only) failed to meet minimum strength criteria, while all chitosan-reinforced variants surpassed both compressive and flexural performance thresholds. Among them, the Chitosan Type 2 wall demonstrated the highest compressive strength at 48.03 KN, making it the most suitable for load-bearing applications. On the other hand, the Chitosan Type 1 wall showed superior flexural resistance, highlighting its potential for withstanding lateral forces, such as those from wind or seismic activity.\u003c/p\u003e\u003cp\u003eNotably, the Chitosan 0.4 wall containing no added cement or lime achieved a favourable balance between structural performance and environmental sustainability. These findings suggest that even small additions of the biopolymer chitosan, particularly when used in combination with mineral stabilizers, can significantly improve the structural integrity of traditional adobe constructions.\u003c/p\u003e\u003cdiv class=\"gridtable\"\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\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eSummary of Structural and Practical Performance of Adobe Wall Types\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCriteria\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eBest Performing Wall Type\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCompressive Strength\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eChitosan Type 2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFlexural Resistance\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eChitosan Type 1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCost-Effectiveness\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eChitosan 0.4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSustainability\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eChitosan 0.2 / Chitosan 0.4 (less cement)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNot Recommended\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSimple (Control)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis research demonstrates the significant potential of bio-friendly materials, specifically chitosan, as effective stabilizers and strength enhancers for traditional adobe structures. The experimental results clearly highlight that the incorporation of chitosan, particularly in combination with lime and cement, substantially improves both compressive and flexural strengths of adobe constructions. Among the tested compositions, Chitosan Type 2 showed the highest compressive strength, making it ideal for load-bearing applications, while Chitosan Type 1 provided superior flexural resistance, enhancing resilience to seismic and lateral forces.\u003c/p\u003e\u003cp\u003eMoreover, the use of chitosan alone, even at minimal concentrations, notably increased mechanical properties, proving its viability as an eco-friendly stabilizer. Given its biodegradability, non-toxicity, and minimal energy consumption during production, chitosan stands out as a sustainable alternative to traditional stabilizing materials. Future research should explore optimizing the proportions and methods of incorporating chitosan into larger-scale adobe structures, potentially paving the way for broader application in sustainable, resilient, and environmentally responsible construction practices.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e This research was supported by a doctoral scholarship from the Funda\u0026ccedil;\u0026atilde;o para a Ci\u0026ecirc;ncia e a Tecnologia (FCT), Portugal [Grant Number: https://doi.org/10.54499/2023.01551.BD.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eCompeting Interests:\u003c/strong\u003e The authors have no conflicts of interest to declare that are relevant to the content of this article.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eK. Behramani, S.V.S. Moghadam. (2012). Earthquake resistant adobe buildings. City Identity.\u003c/li\u003e\n\u003cli\u003eO. Dom\u0026iacute;nguez, A. Garc\u0026iacute;a Hermida, C. Ad\u0026aacute;n. (2014). Stratigraphic analysis of earthen architecture.\u003c/li\u003e\n\u003cli\u003eF. Vise, S. Khoodabandeh, N., Hakaki-Fard, H. V. Tahmasebi. (2009). Providing Appropriate Techniques for the Use of Region Materials. Housing and Village Environment.\u003c/li\u003e\n\u003cli\u003eM. Esmaeili, A. V. Qala-e-Kindi. (2012). The effect of palm and limestone as a stabilizing agent on mechanical properties of adobe. Housing and Village Environment.\u003c/li\u003e\n\u003cli\u003eJ. Warren. (2008). Cultural Institute of Ikomos Iran.\u003c/li\u003e\n\u003cli\u003eY. Wang, J. Liang, X. Zhang, Y. Zhang, Y. Gao. (2015). Review of raw-soil structure in China. China Civil Engineering Journal, 48, 98\u0026ndash;107.\u003c/li\u003e\n\u003cli\u003eR. Sengupta. (1971). Influence of certain Harappan architectural features on some texts of early-historic period. Indian Journal of History of Science, 6.\u003c/li\u003e\n\u003cli\u003eJ. Clifton. (2022). Preservation of historic adobe structures: A status report. SERBIULA (Sistema Libr. 2.0).\u003c/li\u003e\n\u003cli\u003eR.V. Razani, M. Mottahedzadeh, A. V. Razani. (2014). Feasibility Study on Structural Improvement of Buildings Using Nanotechnology. First National Conference on Civil Engineering and Sustainable Development, Tehran.\u003c/li\u003e\n\u003cli\u003eM. Jodat. (2013). Architecture and Sustainable Design. Iran Architecture Quarterly, 14.\u003c/li\u003e\n\u003cli\u003eM. Haghpanah, F. Saghaei, F. Dehghani. (2003). New Structures in Smart Buildings with Sustainable Architecture Approach. National Conference on Sustainable Architecture and Urban Development, Tehran.\u003c/li\u003e\n\u003cli\u003eA. Charleston. (2010). Seismic design for architects. Tehran University.\u003c/li\u003e\n\u003cli\u003eE. Şeng\u0026uuml;n, B. Alam, İ.\u0026Ouml;. Yaman. (2016). Effect of Synthetic Fibers on Energy Absorption Capacity of Normal and High-Performance Concrete. https://hdl.handle.net/11511/79081\u003c/li\u003e\n\u003cli\u003eS.G. Kou, L.M. Peters, M.R. Mucalo. (2021). Chitosan: A review of sources and preparation methods. International Journal of Biological Macromolecules, 169, 85\u0026ndash;94. https://doi.org/10.1016/j.ijbiomac.2020.12.005\u003c/li\u003e\n\u003cli\u003eM. Eslami. (2009). Review of the latest scientific achievements in the field of conservation and restoration of earth materials. Two Special Chapters in Restoration of Cultural Heritage, Isfahan.\u003c/li\u003e\n\u003cli\u003eF. Yang, B. Zhang, C. Pan, Y. Zeng. (2009). Traditional mortar represented by sticky rice lime mortar\u0026mdash;One of the great inventions in ancient China. Science China Series E: Technological Sciences, 52(6), 1641\u0026ndash;1647.\u003c/li\u003e\n\u003cli\u003eS. Kalia, L. Averous. (2011). 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Preparation of chitosan from shrimp shells for the adsorption of heavy metal ions from aqueous solutions using chitosan and hydroxyapatite (Ph.D. dissertation, Shiraz University, Department of Materials Engineering).\u003c/li\u003e\n\u003cli\u003eE.B. Denkbas, R.M. Ottenbrite. (2006). Perspectives on: Chitosan drug delivery systems based on their geometries. Journal of Bioactive and Compatible Polymers, 21(4), 351\u0026ndash;368.\u003c/li\u003e\n\u003cli\u003eM. Rinaudo. (2006). Chitin and chitosan: Properties and applications. Progress in Polymer Science, 31(7), 603\u0026ndash;632.\u003c/li\u003e\n\u003cli\u003eM. Kumar. (2000). A review of chitin and chitosan applications. Reactive and Functional Polymers, 46(1), 1\u0026ndash;27.\u003c/li\u003e\n\u003cli\u003eU.T. Bezerra, R.M. Ferreira, J.P. Castro-Gomes. (2011). The effect of latex and chitosan biopolymer on concrete properties and performance. Key Engineering Materials, 466, 37\u0026ndash;46.\u003c/li\u003e\n\u003cli\u003eM.A. Ashraf, M.J. Maah, I. Yusoff. (2012). Polyvinyl acetate (PVA) as fill material for land reclamation. Chiang Mai Journal of Science, 39(4), 693\u0026ndash;711.\u003c/li\u003e\n\u003cli\u003eM.W. Wan, I.G. Petrisor, H.T. Lai, D. Kim, T.F. Yen. (2004). Copper adsorption through chitosan immobilized on sand to demonstrate the feasibility for in situ soil decontamination. Carbohydrate Polymers, 55(3), 249\u0026ndash;254.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 1 and 3 are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Soil treatment, chitosan biopolymer, green technology, Adobe architecture","lastPublishedDoi":"10.21203/rs.3.rs-6939709/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6939709/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAdobe, a sustainable, inexpensive, and environmentally friendly material, is used in approximately 30% of the world's housing and constitutes 10% of UNESCO's registered heritage sites. However, the long-standing challenge of strengthening clay materials and adobe structures has led to the exploration of various techniques, including the addition of strengthening agents.\u003c/p\u003e\u003cp\u003eThis research investigates the potential of climate-compatible biopolymers as an alternative to traditional soil stabilizers, aiming to develop an eco-friendlier approach to reinforcing earth and adobe structures. Specifically, we explore novel biological technologies for strengthening clay and adobe, comparing their performance against traditional stabilizers.\u003c/p\u003e\u003cp\u003eOur study involves creating various sample combinations using traditional additives like cement, lime, and sand, alongside the bio-friendly material chitosan, at different percentages. These samples undergo laboratory testing to provide a robust and scientific comparison of their properties. Notably, the production of these samples requires minimal energy, suggesting a potentially low embodied energy and reduced greenhouse gas emissions for the final product.\u003c/p\u003e\u003cp\u003ePreliminary mechanical tests, including bending and compressive strength analyses, indicate significant improvements in samples incorporating chitosan.\u003c/p\u003e","manuscriptTitle":"Improving the adobe structures by bio friendly materials","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-23 05:55:36","doi":"10.21203/rs.3.rs-6939709/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":"78181d6d-be12-4268-9a24-8bdb0c7a5236","owner":[],"postedDate":"July 23rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-11-19T16:38:10+00:00","versionOfRecord":[],"versionCreatedAt":"2025-07-23 05:55:36","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6939709","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6939709","identity":"rs-6939709","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}