Bio-Based Building Materials - Proceedings of ICBBM 2025

Polyurethane foams (PUF) are well-known materials in building construction. Innovative biobased polyurethane foams (BPUF) offer competitive alternatives to fossil-based formulations with the ongoing research driven by environmental and health concerns.In this paper, a comparison between an off-the-shelf fossil-based PUF and a custom-made BPUF was conducted. BPUF is based on a chemical formulation that replaces up to 70% of the main fossil-based reactants—polyol and isocyanate—with non-fossil alternatives. Both foams were embedded in the cavity of load-bearing composite masonry units as their insulation layer and binding agent.It was observed that while the density of fossil-based PUF inside the block completely changed from free-foamed declared values, the density of BPUF instead remained consistent to declared values. BPUF has also more (but smaller) number of pores than PUF detected by the microscope. Both types of foam samples were extracted from the block cavities and via dynamic scanning calorimetry (DSC) they were not undergoing any post-curing effects within the temperature working range of interest (10 °C−40 °C) hence they both perform at their best. The combination of such analyses with the results obtained from dynamic mechanical analyzer (DMA) shows that a carefully manufactured, custom-made mid density BPUF can outperform, in average, the mechanical properties of an all-purpose fossil-based PUF in both shear and tensile mode. The latter are stresses applied to the foam when the area of the block is either partially or fully loaded in compression mode. BPUF reached averages of E’ of 33.4 MPa (30 times higher than PUF) at 10 °C and 29.23 MPa (43.62 times over PUF) at 40 °C. In shear mode averages of G’ of 9.27 MPa (12.19 times higher than PUF) at 10 °C and 8.12 MPa (18.45 times higher than PUF) at 40 °C. Furthermore, both types of foam reached the lowest values of elastic modules in tensile and shear mode at their respective glass transition temperature measured by the DSC.

With the increasing demand for sustainable and eco-friendly materials in the twenty-first century, identifying locally sourced substitutes for cement has become crucial for reducing CO2 emissions, minimizing environmental impact, and advancing the principles of circular economy in civil engineering. This study investigates the chemical properties and heavy metals content of biomass ashes derived from agricultural residues in the Vojvodina region of Serbia. The chemical properties of the ashes were analyzed to assess their potential for pozzolanic activity, a key characteristic for their use as supplementary cementitious materials (SCM). Results indicated that several biomass ashes exhibited a favorable chemical composition for pozzolanic reactions, suggesting their potential use in cement-based composites. However, high alkali content was detected, raising concerns about the risk of alkali-silica reaction (ASR) in the hardened cement-based composites. Experimental testing of the ASR mechanism revealed that the expansion due to the reaction between alkalis in the ashes and reactive aggregates remained within acceptable limits. A catalog has been developed to assist potential users in evaluating the biomass ashes for practical applications, featuring comprehensive data on their physical and chemical properties, heavy metal content, alkali-silica reaction (ASR) potential, and environmental impact. This resource provides essential information for assessing their suitability in cement-based composites and other construction materials. These findings underscore the potential of utilizing biomass ashes as a sustainable alternative in cement production, supporting waste valorization, conserving natural resources, and advancing eco-friendly practices in construction, in line with the principles of circular economy and sustainable development.

Fresh properties of calcined and uncalcined laterite based-geopolymer binders means calcined and uncalcined laterite based-geopolymer binders which are just mixed and are about to place in the forms. Properties of fresh calcined and uncalcined laterite based-geopolymer binder controls long term behavior of the calcined and uncalcined laterite based-geopolymer binders. Properties of fresh calcined and uncalcined laterite based-geopolymer binders include workability, air content, temperature and setting time i.e. initial and final setting time etc. This paper presents the review of literature on the fresh properties of materials obtained from alkali activated laterite. The outcomes from this study revealed that calcium–silicate–hydrate (C–S–H), iron–calcium–aluminium–silicate–hydrate (Fe– C(A)SH) and stabilized precursors i.e. laterite and pozzolans had initial setting time of 50, 38, 30, and 53 mins, respectively, while the final setting time were 69, 50, 47, and 70 mins, respectively. This review also demonstrated that there is lack of study on fresh properties such as workability, air content, temperature etc. on calcined and uncalcined laterite based-geopolymer binders. It was also found that calcined and uncalcined laterite based-geopolymer binders have shorter initial and final setting time compared to Portland cement.

The Architecture, Engineering, Construction, and Operations (AECO) sector significantly contributes to global energy consumption and CO2 emissions. In response, the search for more efficient and environmentally friendly materials has intensified. Mycelium, a biological material, has gained significant attention as a circular and low-carbon solution. However, industrial secrecy often restricts the full disclosure of production processes, complicating the replication and comparison of scientific methods. This study sought to address this challenge by developing an experimental protocol and documenting the complete process for cultivating mycelium blocks using coffee husks, an abundant Brazilian agricultural residue. The method consists of five main stages: (1) preparation of the coffee husk residues, (2) inoculation with the Pleurotus ostreatus fungus, (3) colonization in reusable molds, (4) dehydration to halt fungal growth, and (5) evaluation of the blocks’ physical properties. The results demonstrated that blocks made from coffee husks exhibited low density (237.91 kg/m3) and low thermal conductivity (0.07 ± 0.88 W/m∙K.), making them a promising alternative for sustainable thermal insulation in construction. This study contributes to the development of environmentally sustainable building materials with reduced environmental impact and improved energy efficiency. It addresses the growing need for innovative solutions in the construction sector, with relevance to the Brazilian context.

Hemp concrete, the most widely researched bio-aggregate concrete made from hemp shiv and lime, is highly valued in the building envelope for its negative carbon balance, thermal-acoustic insulation, and moisture regulation properties. However, its weak strength and vulnerability limit wider application and make it prone to damage, prompting research to improve its durability and strength without compromising hygrothermal performance and sustainability. This study evaluated the effect of hydroxypropyl methylcellulose (HPMC) on lime-hemp composites, examining their impact on thermal-mechanical and water absorption properties. At the same time, the phase composition of the matrix was studied using Thermogravimetric (TG). Results show that with 0.5–5% dosage, HPMC minimally impacts hemp concrete’s thermal performance but significantly enhances strength and reduces capillary water absorption. Especially adding 5% of HPMC boosts compressive strength by 89%, reduces water absorption by around 21%, and slightly increases thermal conductivity. These effects stem from fiber-bridging, pore-filling, carbonation promotion, and cellulose’s hydrophilic water retention.

The Mythic project addressed the increasing demand for sustainable construction materials by developing innovative insulation products using mycelium bio-composites (MBCs). Centred on circularity and environmental sustainability, the project advanced research across four themes: growth optimization, material properties, prototyping and design, and feasibility and upscaling.In growth optimization, the project enhanced MBC production efficiency while minimizing energy use. Steam pasteurization emerged as a scalable, energy-efficient alternative to sterilization, and reclaimed cellulose as an inoculant improved growth speed and substrate colonization, aligning with industrial production needs.Material properties focused on determining thermal conductivity, fire resistance, water repellence, and moisture behaviour. Thermal and fire performance matched industry standards, while coatings improved durability in humid conditions. Compression and conductivity tests confirmed MBCs’ suitability for insulation applications.Prototyping demonstrated MBCs’ versatility through modular room dividers, insulation panels, and architectural components. User acceptance studies highlighted positive responses to MBCs’ sustainability and biophilic qualities, though challenges like loose fibres and scalability required further refinement.The economic valuation analyses showed potential for cost reductions through process optimization. While lab-scale production costs are higher than conventional materials, scalability and the use of green energy and waste feedstocks could make MBCs cost-competitive. True pricing analysis emphasized their long-term market viability.The Mythic project established MBCs as a viable, sustainable alternative to traditional insulation materials, addressing challenges in scalability, performance, and market acceptance, and paving the way for future research and broader industry adoption.

Additives for mortars and concrete are mainly produced in America and Europe, making them costly and difficult to access for low-income countries. High added value and import costs create economic barriers, limiting local development of construction solutions. The production of stabilized mortar typically requires the use of two classes of additives: air-entraining agents and hydration inhibitors. Organic hydration-inhibiting additives, such as polysaccharides derived from plants like cassava and corn, are more accessible to developing countries. Moreover, their by-products can be more easily produced locally, making them a viable and sustainable alternative. Maltodextrin is a polysaccharide derived from starch hydrolysis, known for its retarding effect in cementitious matrices. However, its potential as an additive in stabilized mortars still requires further research. Thus, this study evaluates the use of maltodextrin as a retarder additive in Portland cement pastes for application in stabilized mortar. The effect of maltodextrin at addition levels of 1.0%, 1.5%, and 2.0%, used with and without an air-entraining admixture, was analyzed, and its effect was compared to that of an industrial inhibitor additive. The pastes were prepared with a water-to-cement ratio of 0.6 and stabilized for 0, 24, and 48 h. After this period the rheological parameters were evaluated by rotational rheometry. The results showed that increasing the maltodextrin content up to 1.0% reduced the yield stress and up to 1.5% for apparent viscosity. The pastes with the maltodextrin were stable compared to the reference sample; however, the inhibitor showed greater activity, especially when combined with the air-entraining additive.

The incorporation of microorganisms into cementitious matrices has been explored as a strategy to enhance the mechanical properties and durability of concrete. Under suitable conditions, microorganisms are capable of producing calcium carbonate, which leads to matrix densification and enables the self-healing of the material. This study investigates the effects of incorporating Bacillus sp. bacteria into cement paste as an admixture, aiming at future applications in concrete with bio-aggregates derived from biological waste. A paste composed by mass of 40% cement, 30% fly ash, and 30% metakaolin was used, with a water-to-binder ratio of 0.4. Initially, an analysis was conducted to determine the optimal bacterial content in the matrix through compressive strength tests on cement pastes with varying percentages (0%, 0.001%, 0.01%, 0.1%, and 0.5%) of bacterial dry mass in the mixing water. Additionally, mixtures were prepared with 1% calcium acetate and 1% calcium acetate combined with 1% nutrient broth to assess the bacteria’s survival capacity in the cementitious matrix and their ability to produce calcium carbonate. Rheological tests indicated lower viscosity for pastes with the addition of calcium carbonate and nutrient broth, suggesting improved workability. Compressive strength improved at intermediate bacterial concentrations (0.01% and 0.1%), while higher concentrations led to reduced performance. The presence of calcium acetate combined with nutrient broth improved compressive strength for all bacterial concentrations. The incorporation of organic components for the bacteria improved the studied properties, and an intermediate bacterial concentration proved to be the most suitable for incorporation into the cementitious matrix.

This study evaluates the feasibility of using plant-based polyurethane derived from castor oil as an elastomer in civil engineering structures, such as bridges, viaducts and precast structures, aiming to replace traditional materials like neoprene and steel bearings. The research focuses on assessing mechanical and durability properties of castor oil-based polyurethane, synthesized through mixing prepolymer (A) and a polyol (castor oil) (B), aligning with sustainable construction practices. Mechanical properties, such as Young’s modulus and shear modulus, were investigated through laboratory tests of three different component mixes of A and B, 1:1,5, 1:2,0 and 1:2,5, in mass. Additionally, tests were conducted with neoprene for direct comparison. The experimental results were compared to recognized standards, including ASTM, Eurocode, and Brazilian Standards (NBR). Ultimately, the study will determine whether this material can meet the demands and performance criteria for including load-bearing capacity and deformation tolerance set by the same codes. The results are promising, suggesting the potential for this material to be used in various structural applications.

The present study aims to evaluate the properties of a tile made from Copiúba waste (Goupia glabra Aubl) and vegetable polyurethane resin, with the effect of reducing waste from timber mills in the Amazon region, giving sawdust waste a viable and ecological destination. The initial tile density of 0.8 g/cm3 was used as parameters, with resin additions in a range of (15% to 30%) of the waste mass. The properties evaluated were: flexural strength, water absorption, swelling and permeability according to the prescriptions of ASTM-D1037 and NBR-13310/2005. The results demonstrate that tiles made with wood residue and vegetable resin suits to the normative parameters of tiles in terms of load capacity and water absorption, with performance proportional to the addition of resin to the mixture, thus making it viable to use this residue for production of ecological tiles.

Nowadays, the construction sector is responsible for a significant part of energy related global carbon emissions. In this context, the wood bio-concrete (WBC) emerges as an environmental-friendly alternative to conventional lightweight concrete by utilizing industry vegetal residues as aggregate, which enhance its energy efficiency. However, due to its organic content, the WBC has a high water absorption capacity that is detrimental to its physical-mechanical properties and durability. Researchers have tackled this issue by integrating a silane-siloxane-based water repellent into the cementitious matrix of the material, which, although mainly beneficial, directly affects the bio-concrete’s workability thus altering its hardened state properties. Therefore, this work aims to optimize the cementitious matrix of wood bio-concrete with incorporated silane regarding its bio-aggregate and superplasticizer proportions, seeking improvements in its workability, mechanical and physical properties. For this purpose, samples were produced in two types: one volumetrically composed of 45% bio-aggregate (WBC45), and the other with 35% of bio-aggregate (WBC35). Both samples had superplasticizer added as additive to the mixture in concentrations varying between 0%, 0.5% and 1.0%. In all mixtures, 2% of water repellent was incorporated. The experimental procedures included the following tests for the fresh and hardened states: flow table, incorporated air content, uniaxial compression, and capillary water absorption. As main results, the addition of 0.5% of superplasticizer resulted in improved rheological behavior for the WBC35 samples and enhanced physical-mechanical properties for the WBC45 samples.

Phase change materials (PCMs) can improve energy efficiency of buildings, reducing energy consumption and improving thermal comfort. PCMs have reportedly been contained by porous materials such as natural fiber textiles, which can be applied as reinforcement for cement matrices in building materials. This work aimed to investigate the effectiveness of different polymer coating treatments to coat jute textiles containing PCM, preventing leakage. Three treatments were studied: carboxylated styrene-butadiene rubber (XSBR); XSBR with 5% ZnO addition; carboxylated nitrile rubber (XNBR). In order to evaluate the effect of the treatments on jute’s mechanical properties, tensile and pullout tests at both solid and liquid state PCM conditions were performed, as well as and chemical characterization of the textiles. Results have shown that XNBR coating provided higher a tensile strength (77 MPa at both conditions) and a higher adhesion strength to a cement matrix (12.6 N and 15.7 N at liquid and solid PCM conditions, respectively) to jute yarns when compared to XSBR, while also effectively coating fibers with a thinner and lighter coating layer, demonstrating its potential for this application.

One of the primary challenges in achieving sustainable development is managing the waste generated by human activities, particularly from industrial processes. In this context, waste from the furniture industry can be repurposed into valuable products for building construction. However, there is a lack of previous research on the effects of air-entraining admixtures (AEAs) and water-retaining admixtures (WRAs) in cementitious matrices with furniture industry waste. To address this research gap, this work aimed to assess the technical feasibility of producing recycled masonry mortars by replacing Portland cement with wood ash and sewage treatment plant sludge, and incorporating varying dosages of AEAs and WRAs. The results showed that all mortars containing WRA maintained water retention levels above 95%, classifying them as materials with strong water retention. For mortars with lower ash content, air entrainment increased with AEA dosages values up to 0.002%, after which it stabilized, signaling a saturation point. Mortars with higher ash content exhibited a continuous increase in air entrainment as the AEA dosage increased. The combination of AEA, WRA, and different types of furniture industry waste appears to be a promising approach for producing recycled masonry mortars.

Energy consumption stands out as one of the factors responsible for the emission of greenhouse gases, through the use of non-renewable energy sources, generating serious impacts on the environment. Due to this reality, the issue of energy efficiency has gained ground, especially when it is related to civil construction. Thus, the application of insulating materials in constructions has been an intelligent strategy, which enables energy efficiency, reducing energy consumption. Phase Change Materials (PCM) promote the delay of heat propagation and thermal damping, which results in increased thermal comfort. Therefore, the incorporation of encapsulated PCM in a cement matrix has proven to be an efficient means. Thus, the theme of this work will be the review of the application of PCM in cement matrix, since the objective of this article is to discuss its potential incorporation, through a bibliographic review, considering its classification, form, application and potential difficulties for such incorporation .

The global reliance on Ordinary Portland Cement (OPC) has raised significant environmental concerns, with cement production contributing to 5–7% of global CO₂ emissions. Geopolymer concrete (GPC) has emerged as a promising sustainable alternative, leveraging industrial by-products like fly ash (FA) and ground granulated blast furnace slag (GGBFS) to mitigate the ecological footprint of traditional construction materials. This research focuses on the slump, slump retention, and durability performance of geopolymer concretes under chemical conditions, comparing three distinct mixes: a geopolymer concrete with 25% GGBFS and 75% FA (UoM), a 100% FA geopolymer mix (MU), and conventional OPC concrete. Durability tests included acid resistance, sulphate resistance, and supported by advanced microstructural analyses such as X-ray diffraction (XRD) and scanning electron microscopy (SEM/EDX). The findings demonstrate that geopolymer concretes exhibit enhanced resistance to chemical degradation, lower permeability, and reduced mass and strength loss compared to OPC based concrete. The slump retention values show that the geopolymer concrete can retain slump values for up to 40 minutes; this positions geopolymer concrete as a viable solution for sustainable construction in aggressive environments.

This study introduces a multicriteria assessment framework designed to accelerate the adoption of bio-based materials in the construction sector by systematically evaluating their value and impact compared to conventional materials. Bio-based materials, such as those derived from hemp, bamboo, and timber, offer considerable potential to contribute to a regenerative, net-zero built environment that enhances occupant health, supports local economies, and reduces environmental impacts. However, their adoption remains limited due to persistent barriers, including stakeholders’ resistance, insufficient market awareness, higher costs, and technical challenges.To address these issues, this research develops a streamlined assessment framework that evaluates the potentials and impacts of bio-based materials across five dimensions: human, social, natural, financial, and manufactured capital. The development methodology of the framework includes setting strategic objectives, defining key performance indicators (KPIs), and applying the framework to evaluate two bio-based construction systems developed by the SmartBioC research group - one fast-growing and one timber-bamboo - alongside a conventional system based on bricks and synthetic materials, as well as a system meeting Passivhaus energy standard. This comparative analysis employs a scoring mechanism to quantify and highlight the advantages and trade-offs of each system.Preliminary findings suggest that bio-based materials, particularly fast-growing ones, deliver broader and more balanced benefits across the five capitals compared to conventional construction materials. Future work will focus on refining the framework by incorporating stakeholder feedback to enhance its applicability and foster the broader integration of bio-based materials within the construction industry.

This study evaluates the potential of UK-grown hardwood and softwood fibres for thermal insulation to support locally sourced, low-carbon construction materials. A Multi-Criteria Decision-Making (MCDM) framework, incorporating availability, fibre length, fibre content, and dry wood density, identified birch, poplar, sycamore, ash, and alder as top hardwood candidates. Due to reduced ash availability caused by ash dieback disease, beech was substituted. Fibre characterisation revealed that poplar had the longest fibres among hardwoods, while sycamore ranked high for availability and fibre content on the MCDM but exhibited the shortest fibres. Sycamore’s shorter fibres and alder’s limited availability suggested a blended approach could optimise insulation properties. Beech fibres demonstrated favourable length but higher bulk density, warranting future comparisons of insulation products made from beech versus poplar fibres to assess the impact of bulk density on thermal performance. Among softwoods, Sitka spruce was identified as a strong alternative to larch, based on availability and fibre properties.

Building materials emit 250 million tons of CO2 annually, aggravating environmental impacts. Natural fiberboards offer a sustainable alternative. 100% coriander-based fiberboards are promising due to their lack of formaldehyde emissions. After harvest, coriander fruits undergo thermo-mechanical pressing and solvent extraction to extract vegetable oil. The resulting press cake is then mixed with extrusion-refined coriander straw, and thermopressed to obtain the coriander boards, proteins from the cake acting as a natural binder. A preliminary study optimized the hot pressing, and conditions to achieve flexural properties comparable to commercial medium density fiberboard (MDF) were identified. The present study compares the environmental performance of coriander fiberboard with commercial MDF using an attributional life cycle assessment. The functional unit is defined as the production of 1 m2 of coriander fiberboard, intended for use as a partition wall, following a cradle-to-gate approach in France. Data collection was based on experimental studies conducted at TRL 5 to 6. Results show that producing the MDF-like board from coriander has a greater advantage in terms of reducing CO₂ emissions compared to the production of conventional MDF. Furthermore, the cultivation and harvesting stage of coriander was identified as the primary contributor to pollution across several impact categories.

The concept of circularity has gained momentum in recent years to reduce the amount of waste generated by a construction project and the need for new materials. This paper explores the different circularity potentials of using 1 m2 of biobased insulation materials (BbIMs) with various origins (plants, animals, or recycled) and forms (loose fill, blocks or panels) along 100 years. The BbIMs under investigation are commercial insulations including straw, cork, wood fiber, wood wool, prairie grass, cellulose, cotton, sheep wool, and hemp. The circularity potentials of these insulations are evaluated by calculating the Material Circularity Indicator (MCI). The findings highlight varying circularity potential among the different BbIMs, with the MCI ranging from 0.18 to 0.9. Notably, cellulose insulation, both blown and in panel forms, achieved the highest circularity scores due to their significant content of recycled and renewable materials and efficient recycling processes at end-of-life (EoL). The results emphasize the importance of designing insulation solutions with closed-loop systems to promote circularity.

Biomaterials are an alternative to the reliance on non-renewable raw materials and have the potential to reduce emissions of CO2 during their transformation processes, aiming to decrease their overall carbon footprint. Different Life Cycle Assessment (LCA) methodologies have been applied to understand the impacts of incorporating these materials into the construction industry, but the varieties of LCA methods and the limited number of studies make the best methodology a challenge. For this purpose, a literature review was conducted using the Web of Science database, to search for scientific articles in English, combining different keywords in three groups with the use of logical operators AND and OR: (LCA OR Life Cycle Assessment) AND Bio-based materials AND Building, (LCA OR Life Cycle Assessment) AND bio-based materials AND Construction, Biogenic AND carbon AND building AND sector AND (LCA OR Life Cycle Assessment), between the years 2015 and 2024, applying the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 (PRISMA) methodology, with exclusion criteria: keywords, title, abstract, and duplicate articles. Furthermore, reports and policies were used as inclusion criteria. A case study on insulating components will be conducted to examine the values reported in Environmental Product Declarations (EPD). The results show that the lack of standardization in the scales of bio-based products can be one of the barriers faced in expanding the use of these products.

The excellent insulation properties and low carbon footprint of plant-based concretes make them increasingly popular in construction. To produce optimized building materials, it is crucial to better understand the interfacial transition zone (ITZ) between plant particles and cement paste, focusing on the reactions involved and the size of the affected surface. This research established a reliable visual test to observe the ITZ, allowing for the monitoring of its formation and development. Various combinations of plant particles and cement pastes were tested to compare the ITZ formation, including hemp and bamboo with Portland, Prompt, calcined clay limestone, and pozzolanic cements. A clear correlation was found between sugar concentration and ITZ size. Image analysis revealed that the ITZ results from physicochemical reactions, involving the extraction of free saccharide molecules from the plant particles and water absorption, followed by their release into the cement paste.

Microbially Induced Calcium Carbonate Precipitation (MICP) has recently emerged as an environmentally friendly technique with various applications, including water remediation, soil quality improvement, oil and gas engineering, and the repair and maintenance of cementitious construction materials. Although MICP has been observed in many groups of microorganisms, most research to date has focused primarily on bacteria, with other microbial representatives largely overlooked. This study, therefore, aims to investigate the potential of yeasts isolated from construction materials to produce CaCO₃, with the purpose of enhance the quality of demolition waste for future reuse. Using classical microbiological methods based on a selective medium supplemented with calcium acetate, three distinct colonies differing in color and morphology were selected and labeled as LCEQ1, LCEQ2, and LCEQ3. Each yeast isolate was then individually inoculated into 500 mL Erlenmeyer flasks containing 100 mL of a production medium optimized for CaCO₃ precipitation. All flasks were agitated at 150 rpm at 30 °C for 7 days, with a control flask without microbial inoculum maintained under identical conditions. After incubation, a white precipitate was visibly observed in all yeast-inoculated flasks, and FTIR analysis confirmed the presence of CaCO₃. No precipitate was observed in the control flask. The amount of calcium carbonate was measured through thermogravimetric analysis. Among the three isolates, yeast LCEQ2 demonstrated the highest acetate-to-carbonate conversion (56.3%), followed by LCEQ3 and LCEQ1. These findings suggest that concrete aggregates may serve as a promising source of yeasts capable of precipitating calcium carbonate.

Reinforced cement concrete (RCC) structures are prone to corrosion due to the formation of micropores during casting. These micropores develop by entrapping air during the mixing and casting of wet concrete, leading to irregularities in the concrete matrix. This inherent property of cementitious construction compromises the material’s integrity, reducing compressive strength and increasing water absorption, which shortens the service life of the structure. Corrosion is further exacerbated by exposure to moisture and aggressive environmental factors, which penetrate through these pores and cracks. Preventing corrosion in cementitious structures requires sealing the pores and improving the matrix’s durability. Microbially Induced Calcium Carbonate Precipitation (MICCP) has been proposed as a bio-inspired solution for self-healing cementitious materials. In this process, the bacteria mixed in concrete consume nutrients and precipitate calcium carbonate, effectively filling the pores and healing cracks. This microbial activity also creates a protective layer, reducing the ingress of harmful agents like water and chemicals, thereby mitigating corrosion risks. Monitoring the effectiveness of MICCP in preventing corrosion is critical.This study employs non-destructive (NDT) ultrasonic pulse transmission to monitor bacterial self-healing in real-time. The amplitude of the ultrasonic waves passing through the bacterially treated specimen increases as treatment progresses, indicating the gradual closure of pores and defects. The enhanced compressive strength observed in treated specimens over 28 days further confirms the effectiveness of bacterial healing. This non-destructive ultrasonic monitoring approach offers a reliable method for assessing and managing corrosion prevention in cementitious structures and further correlation studies helped to predict the internal health of civil structure non-destructively.

Microbial-induced calcium carbonate precipitation (MICCP) is a promising technique for self-healing concrete applications. Microbes, through different metabolic pathways, produce carbonate ions which then react with calcium ions (Ca2+) present in the surrounding environment and result in calcium carbonate (CaCO3) precipitation. The presence of bacterial cells with negatively charged cell walls provides nucleation sites that bind with positively charged Ca+2, allowing crystal growth and stabilization. However, this process heavily depends on bacterial viability and growth. Subsequently, direct use of the enzyme responsible for this activity known as EICP (Enzyme-induced carbonate precipitation) has emerged. This more controlled reaction allows for faster CaCO3 production. However, the absence of cell walls leads to the lack of nucleation sites necessary for growth and binding of crystals. To resolve this issue, the present research aims to use gelatin, a negatively charged biological hydrogel, to provide nucleation sites that enhance EICP. Different concentrations of Gelatin type B (isoelectric point: 4.7–5.3) were mixed with the enzyme urease (extracted from bean meal), urea and calcium acetate, and incubated for 24 hours at room temperature The resulting precipitates were characterized by X-ray diffraction and scanning electron microscopy to identify the mineral phases. The results indicate that an increase in the concentration of hydrogel leads to an increase in the formation of various polymorphs of calcium carbonate (i.e. vaterite, calcite, and aragonite) and interestingly, a decrease in the total amorphous phase. This implies that incorporating the hydrogel promotes crystalline phase production which can be beneficial for achieving more stability in self-healing applications.

In recent years, the scientific community has shown interest in developing self-healing cementitious matrices. To understand the current state of this topic, the objective was to carry out a systematic review of the literature (RSL) on self-healing concrete in Latin American databases. Given this, the work methodology consisted of an exhaustive search of articles published in the databases: Scielo, Latindex, Redalyc, and Dialnet, within the period 2018 to 2023. Through Google Scholar, 115 documents were identified and, after applying criteria exclusion, 13 scientific articles were selected. The results indicate that microorganisms, particularly Bacillus subtillis, are the most studied within a self-repairing cementitious matrix; however, the results are influenced by other variables, such as the amount of the microorganism, application method, type, and state of the cementitious matrix, among others. Therefore, it is necessary to carry out more experimental studies that allow a more precise understanding of the behavior of the existing variables within the development of a self-healing concrete.

Concrete, widely used in construction for its strength and affordability, faces susceptibility to cracking under tension, posing a risk to its internal structure. To mitigate this issue, several autogenous healing technologies have been developed, including the use of microencapsulated chemicals, engineered cementitious composites, and bacterial incorporation, all of which are effective for fresh concrete. However, healing sub-surface cracks in aged concrete remains a significant challenge. This study focuses on the development of an advanced delivery system that combines a hydrogel-assisted method with a vascularized approach to transport biological components into sub-surface cracks and facilitate healing through microbial-induced calcium carbonate precipitation (MICCP). In the present study, artificial cracks were introduced in cylindrical mortar specimens to simulate subsurface damage. Using micro-drilling, engineered channels - similar to arteries - were created to reach the crack network to create an interconnected vascular network. Two different hydrogels were used for bio-agent delivery in the vasculature network to create a self-repairing paradigm. After evaluating their transport properties, the most suitable hydrogel was selected for delivering a biological solution containing nutrients (yeast extract, urea), bacteria, and calcium acetate into the cracks. A systematic injection of the nutrient-rich biological solution and calcium source was then implemented to enhance microbial carbonate mineralization and promote crack healing. To quantify the calcium carbonate precipitation resulting from microbial activity, thermogravimetric analysis (TGA) was conducted at 7 days. Results indicated that the hydrogel-assisted approach shows promising potential in effectively delivering biological agents deep within concrete cracks, promoting self-healing through microbial-induced calcium carbonate precipitation.

Concrete degradation, caused by cracks and fissures, presents a significant sustainability challenge for the construction industry, with direct implications for maintenance costs and CO₂ emissions. This study aimed to develop porous capsules for self-healing concrete applications, employing volcanic aggregates as carrier agents due to their high porosity and mechanical stability. The capsules were produced through vacuum saturation using sodium silicate as a healing agent and coated with polyvinyl alcohol (PVA) as a barrier material to facilitate self-healing in cementitious materials. Capsules with diameters ranging from 2 to 8 mm were characterised through sphericity and circularity measurements, porosity testing, compressive strength analysis, and chemical composition determination using FTIR-ATR spectroscopy. Results showed efficient encapsulation, achieving saturations of up to 53.13%. The addition of 6% PVA coating increased capsule compressive strength from 2.15 to 2.47 MPa, ensuring their survival during the concrete mixing process. In conclusion, the developed capsules demonstrate potential for incorporation into concrete for self-healing applications, thereby extending the service life of structures while simultaneously reducing maintenance costs and CO₂ emissions associated with cement production.

The aim of this study is to provide a comprehensive analysis and characterization of various bio-based materials, aiming to explore their potential applications to incorporate them in construction materials. The materials investigated include rice husk, olive tree branches, olive pits, Posidonia oceanica, corn stalk, sunflower stalk, luffa, hemp stalk, and wheat straw. These materials were selected for their abundance and renewable nature, making them attractive candidates for sustainable building materials. A suite of analytical techniques was employed to thoroughly investigate the properties of these materials. X-ray fluorescence (XRF) was used to determine the elemental composition, Fourier-transform infrared spectroscopy (FTIR) provided insights into the functional groups and chemical bonds present, thermal gravimetric analysis (TGA) assessed the thermal stability and decomposition profiles, which is a valuable information that can be correlated with the fire reaction behaviour. Thermal conductivity and diffusivity measurements were conducted to evaluate the insulation properties, with some materials showing promise as effective thermal insulators. Particle analysis by means of image analysis using ImageJ software facilitated a quantitative assessment of particle sizes and distributions, further elucidating the physical characteristics of the materials. Scanning electron microscopy (SEM) observations allowed for detailed morphological analysis, highlighting the microstructural differences and similarities among the materials. Overall, the findings underscore the diverse properties of these bio-based materials, suggesting that specific materials or combinations thereof can be optimized for its application in the construction sector in different applications such as thermal insulation materials or pozzolanic additions. This study not only advances the understanding of the inherent properties of these renewable resources but also provides a foundation for developing sustainable building materials with enhanced performance characteristics.

Hemp-lime is a bio-based material with an embodied energy of around 300 to 800 MJ/m3 [1], compared to 2100 MJ/m3 for reinforced concrete [2] and roughly 3000 MJ/m3 for the main conventional insulating materials [3]. Its limitation lies in its mechanical properties, it is too weak to bear loads. Despite this, a significant body of research has yielded detailed results on various hemp-lime formulations, some of which include additives that enhance the mechanical properties.However, it remains challenging to find comprehensive studies that evaluate the effectiveness of the main additives employed in hemp-lime mixtures [4], such as gypsum, quicklime, pozzolana so that both carbonation and hydraulic setting are shown during the setting; and that compare such behaviour with that of mixes which employ hydraulic lime as the sole binding agent.By adopting a scientific approach grounded in physical and chemical methodologies, this study presents a characterization of four different mixtures, each incorporating two distinct hemp combinations composed of hurds and fibres. The study aims to assess carbonation levels over various periods using phenolphthalein as a pH indicator, as well as the mechanical properties of elasticity and compressive strength through a wide sampling campaign.The mixture exhibiting the best mechanical strength is the one containing hydraulic lime. Moreover, its carbonation is notably more pronounced compared to mixtures based on air lime, depending on the specific additive used. However, when examining the evolution of the modulus of elasticity over time, it is evident that the inclusion of quicklime and pozzolana (mixtures A and A’) achieves strength values comparable with those of hydraulic lime (mixtures D and D’). This improvement is also correlated with the depth of carbonation observed in various areas of the samples.This work suggests that improvements in the mechanical behaviour of hemp-lime could be achieved through specific additives, depending on the desired characteristics. Hemp-lime could evolve into a range of materials with distinct properties, which could be exploited in various construction applications.

This study investigates the durability of red ceramic blocks produced by two different methods: pressing and firing (BPQ) and extrusion, pressing and firing (BCEPQ). The blocks were manufactured in the municipality of Campos dos Goytacazes with the collaboration of Arte Cerâmica Sardinha, using an Eco Master 7000 Turbo II Press for the pressing stage. Mechanical and technological characterization tests were performed on BPQ and BCEPQ blocks, both with and without degradation process. The degradation process included chemical attack and wetting/drying cycles to simulate changes in the ceramic material. The study analyzed chemical attack durations of 168, 336, and 504 h, along with 100 wetting/drying cycles (totaling 2,400 h) The results showed that the drying and wetting cycles were significantly affected by the crack patterns formed during the block production due to shrinkage in the drying and firing stages. However, BCEPQ blocks demonstrated better performance in terms of mechanical strength and water absorption rate compared to BPQ blocks.

Mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) were employed to evaluate the influence of pig hair fibers on the gel pore volume and cement microstructure of concrete aged one year. Cubic concrete samples (15 cm per side) were subjected to three different external curing conditions. The samples were subsequently sectioned into three layers based on the moisture diffusion profile imposed during curing: layer A, exposed to the highest moisture gradient, and layers B and C, subjected to progressively lower moisture gradients. MIP results indicated an increase in gel pore volume (<25 nm) in layer A of the fiber-reinforced concrete compared to plain concrete cured for one year at 50% relative humidity (RH). Furthermore, a progressive increase in gel pore volume was observed in samples pre-saturated for 77 and 156 days before being cured at 50% RH for the remainder of the year. These findings demonstrate that internal curing of concrete can be effectively promoted using natural fibers.

This study examines the applicability of Washburn’s law for predicting capillary rise in vegetal concretes, with a focus on practical applications. The findings contribute to the groundwork for service life modeling of these materials. Initial results demonstrate a strong correlation between the capillary rise predicted by Washburn’s law and experimental observations across four mixes of hemp shiv and rapeseed straw, both with and without a viscosity-modifying agent. However, discrepancies emerged during later stages of the experiments, attributed to the finite dimensions of the samples and gravitational effects.

In the transition towards a circular economy, using waste and byproduct substances is gaining significant attention in construction materials for their potential to enhance sustainability. This study investigates the long-term properties of ternary grout systems incorporating wood-based biochar and coal fly ash as partial Portland cement (PC) replacements. Biochar, produced from wood biomass, was added in the 0–15% range, alongside a fixed 25% fly ash content. The research evaluated the workability of the grouts (via a mini-slump flow test) and mechanical properties (flexural and compressive strength) after 56- and 210 days of curing. Durability after exposure to 50 freeze-thaw cycles, and water absorption across five different mixes after 210 days of curing was also investigated. The results indicated that biochar additions up to 10% had a beneficial impact on flexural strength but led to a decline in compressive strength due to its high porosity. However, including 25% fly ash partially compensated for the loss in compressive strength due to pozzolanic reactivity, contributing to a denser matrix over time. Mixes containing biochar (up to 10%) demonstrated superior freeze-thaw resistance, exhibiting lower reductions in flexural strength after accelerated aging, compared to those with only fly ash. This synergy between biochar’s carbon sequestration potential and fly ash’s pozzolanic activity could maintain grout performance while reducing the environmental impact, owing to a reduction in PC usage by over 35%.

Aggressive agents can significantly affect the durability of reinforced concrete structures. To ensure long-term performance, these materials must retain their integrity under such conditions, serving as a protective barrier against substances that could induce the corrosion of embedded reinforcements. Corrosion arises from carbonation and the action of chloride ions, which can penetrate into concrete through convection and diffusion mechanisms. Opuntia Ficus-Indica (OPI) has been used as a bio-inhibitor that also reduces the chloride ion penetration into cement-based matrices. This extract works by chemically bonding with water molecules, aggressive agents, and pectins, effectively blocking the pores within the concrete structure and enhancing its resistance to degradation. In this study, a high-early strength Portland cement was used for mortar production, with a water-to-cement ratio (w/c) of 0.5. Eight different mixtures were prepared: a reference mixture, four mixtures where OPI mucilage partially replaced the mixing water at proportions of 4%, 6%, 8%, and 10%, two mixtures where powdered OPI extract partially replaced the cement at proportions of 1% and 2%, and one mixture incorporating a commercial corrosion inhibitor. This study evaluated the influence of OPI extract content on the compressive strength of these mixtures, as well as on the chloride ion migration in the studied mortars, in accordance with the NT BUILD 492 standard. Results show that the use of OPI can reduce the rate of chloride ingress into concrete acting as an additional barrier to protect the reinforcement.

To decrease the water absorption capacity of hemp fibers and increase the final mechanical properties of short hemp fiber-reinforced fly ash-based geopolymer mortars after exposure to 10 wet/dry cycles, two distinct fiber treatments were employed, i.e., fiber hornification (with 5, 10, or 15 cycles) and NaOH treatment (with 3%, 6%, or 9% of NaOH). Both treatments proved to increase the final mechanical properties of non-treated hemp fiber-reinforced geopolymers after exposure to 10 wet/dry cycles. After wet/dry cycles, when the geopolymers were reinforced with the hornificated fibers, the compressive strength increased up to 80%, flexural strength up to 22%, and energy absorption capacity up to 18% in comparison to the geopolymer reinforced with non-treated fibers. Similarly, the geopolymers reinforced with NaOH treated fibers, after being exposed to wet/dry cycles, resulted in a 49%, 25%, and 19% increase in compressive- and flexural strengths, and energy absorption capacity, respectively, compared to its counterpart reinforced with non-treated fibers.

This study evaluates bio-stabilised cob’s structural and thermal performance for sustainable buildings. Thirty-three cob mixes were analysed: subsoil, water, and natural fibres—hempshiv and barley straw—with fibre contents ranging from 1% to 10% and water contents ranging from 20% to 30% by volume. Unstabilised samples of subsoil and water served as baselines.X-ray diffraction revealed the subsoil contained 70% quartz, while the fibres were predominantly cellulose. Scanning electron microscopy showed the subsoil had a compact structure with 20.34% porosity, whereas hempshiv and barley straw were more porous, with 29.94% and 42.78%, respectively.Adding fibres significantly reduced thermal conductivity compared to unstabilised mixes. The lowest thermal conductivity was 0.132 W/m·K for a mix with 7% barley straw and 30% water, while the highest was 0.378 W/m·K for the unstabilised mix with 20% water. Higher densities correlated with higher thermal conductivity.Compressive strength decreased with increased fibre content, with hempshiv causing a smaller reduction than barley straw. The highest compressive strength was 1.719 MPa for a mix with 5% hempshiv and 25% water; the lowest was 0.785 MPa for a mix with 7% barley straw and 25% water. Volumetric shrinkage increased with higher fibre and lower water contents.The mix with 3% hempshiv and 30% water content demonstrated optimal performance: thermal conductivity of 0.163 W/m·K, compressive strength of 1.454 MPa, density of 1,676 kg/m3, and volumetric shrinkage of 16.4%.This research highlights the importance of analysing cob’s constituents to optimise its properties, supporting cob’s potential as a sustainable construction material for decarbonising the built environment.

Conceptualized, realized, monitored, recorded and deconstructed over eighteen months, the Raw Earth Sgraffito Pavilion, located in a semi-public Parisian courtyard, is a case study for the sourcing, performance and end-of-life for earth building materials. All the pavilion’s materials were mapped from source to site, then assessed for CO2 impact. The resulting map appears in the decorative sgraffito surface. For its duration, the pavilion was monitored for weathering and, in summer ‘24, for temperature and hygroscopic characteristics. Results demonstrate thermal lag and higher moisture levels around the structure and reveal micro-fluctuations that ratify passive strategies (such as shading, orientation, and night flush) for optimal performance. At end of life, the pavilion was deconstructed, its salvaged blocks reused for training, and fragmented earth plaster and mortar made into a slurry for other earthen building. Plywood used for seating and weather protection was repurposed by an artist for a new project.

The rapid growth of the construction sector has intensified the demand for building materials, increasing pressure on natural resources and exacerbating environmental challenges. The clay brick industry, characterized by high energy consumption, faces significant prodution costs due to the elevated firing temperatures required, alongside environmental concerns such as substantial carbon emissions. The partial substitution of clay with ashes emerges as an eco-friendly solution to reduce excessive energy consumption and mitigate the environmental impacts of brick manufacturing while valorizing industrial waste. This study aims to enhance the energy efficiency of fired clay brick production by utilizing co-products from the olive industry, specifically Olive Pomace Combustion Fly Ash (OPCFA). A 3% OPCFA content was incorporated into the clay matrix, followed by controlled drying and firing cycles, with firing temperatures progressively reduced from 850 ℃ to 750 ℃. The reduction in firing temperature resulted in increased porosity and improved thermal insulation properties while maintaining mechanical performance within construction standards. These enhancements are attributed to the fluxing oxides in the ash, which facilitate vitrification at lower temperatures.Microstructural analyses, including scanning electron microscopy and nitrogen porosimetry, confirmed the influence of reduced firing temperatures on pore structure and material performance. The findings demonstrate that incorporating OPCFA not only lowers firing temperatures and energy consumption but also enhances the thermal and mechanical properties of the bricks. This approach offers a sustainable and practical pathway to advancing the environmental and economic sustainability of brick manufacturing.

Bio-based materials, valued for their low environmental impact, sometimes exhibit a vulnerability to fire, which limits their use in construction. This study investigates the use of earth mortars to improve the fire resistance of bio-based earthen blocks masonry. The blocks were manufactured by extrusion earth using earth combined with sawdust. The earth mortars were formulated using an optimized mixture of silty-clay earth combined with silica-calcareous sand or fired brick waste. These were applied either as 10 mm thick bedding mortars on small wall samples composed of three blocks, or as 20 mm thick coatings on these wall samples. Three groups of wall samples were tested: uncoated walls, walls coated with the earth-sand mortar, and walls coated with the earth-brick waste mortar. The walls were subjected to a unidirectional heating cycle (10 ℃/min up to 800 ℃) to evaluate thermal stability and the capacity of the bedding and coating mortars to act as protective barriers. Thermocouples were used to monitor temperature evolution at different depths. After cooling, the uncoated walls showed vertical cracks and failure of the bedding mortars. For the coated walls, detachment was observed between the coating and the masonry, attributed to differences in the thermal expansion of the materials. The earth-sand coating showed cracks due to calcite decarbonation, reducing their efficiency. In contrast, the coating containing brick waste was free of cracks and showed better thermal stability. These results highlight the potential of earth-brick waste mortars to enhance the fire safety of bio-based earth masonry while providing a sustainable and innovative solution.

Nowadays, the construction sector has a strong negative impact on the environment. In order to reduce this impact, alternatives to conventional building materials should be found and used for sustainable construction. In this respect, earthen construction is a viable solution due to its low transformation process. Highly developed in Mayotte from the 1980s to the 2000s, the Compressed Earth Block (CEB) industry is now in decline on the island. Most of the current CEB production uses cement, manufactured off the island, as a hydraulic stabilizer, which has a significant environmental cost. In the literature, research has focused on the potential of bio-additives to improve some properties of earthen building materials, thus reducing the carbon footprint of the material. This study, conducted on Mayotte soil, considers the use of local bio-based and minimally processed by-products as bio-additives for CEB to improve their compressive strength. The effects of three bio-additives are studied for mass concentrations ranging from 1% to 20%. The results show that the bio-additives improve the compressive strength of CEB by up to 37%.

This study explores the application of Terra Rossa (reddish clay soil) from the Apulia region (Southern Italy) as a partial replacement for sand to produce one-part geopolymer mortars. Firstly, the work involved characterizing Terra Rossa (TR) using density measurements, granulometry, thermogravimetry analysis (TGA), scanning electron microscopy (SEM), and X-ray diffractometry (XRD) to assess the soil’s properties. Then, for designing geopolymer mortar mixtures, TR was used in two forms, “as received” and sieved to < 1.7 mm, and replaced 50% of the sand component in the mixture. The samples were cured under two conditions: room temperature for 28 days, and another process involving heat treatment at 70 °C for 24 h followed by room temperature curing for 27 days. Mechanical strength, workability (slump), water absorption, and microstructure of the produced geopolymer mortars were examined. The present research highlights the potential of TR as a sustainable and locally sourced feedstock for geopolymer materials synthesis, providing a basis for further exploration of its use in non-structural building and architectural applications and contributing to the advancement of greener construction practices.

The high energy consumption in buildings has become a global concern. Phase Change Materials (PCM) offer a potential solution for enhancing building energy efficiency, as they help stabilize indoor temperatures, thereby reducing the need for artificial heating, ventilation, and air conditioning systems. In this study, a bio-based PCM was impregnated into Rice Husk (RH) to produce bio-aggregates, which were then incorporated into lime-cement earth mortar. Due to its porous structure, RH is capable of absorbing and retaining PCM, acting as a carrier, resulting in the formation of shape-stabilized RH-PCM. The physical properties (including density and water absorption) of the bio-aggregate were assessed. RH-PCM was incorporated into the mortars at contents of 4% and 8% to assess its influence on the mechanical behaviour. Mixtures containing only RH (without PCM) were also evaluated for comparison. The study analysed both flexural and compressive strength. The results indicated that the incorporation of PCM into the RH reduced the water absorption of the bio-aggregate. Also, the bio-aggregates (both RH and RH-PCM) led to a reduction in compressive strength compared to the control mortar (without bio-aggregates). However, the inclusion of PCM into RH did not significantly impair the mechanical performance of the mixtures when compared to mortars containing only RH.

As the tide retreats, large quantities of seaweed are left stranded along the coastline, and the resulting accumulation of marine macroalgae presents a serious environmental concern. This study investigates the potential large-scale use of stranded macroalgae in building materials. Specifically, it explores the impact of incorporating seaweed at varying proportions in both lightweight and structural cob. A thorough analysis of earthen wall samples was performed to assess their compressive strength and hygrothermal properties. For lightweight earth, improvements were observed in thermal storage capacity and conductivity, without compromising compressive strength. The optimal seaweed content was found to be 20%, leading to a 26% reduction in thermal conductivity compared to traditional cob. The addition of algae significantly enhanced both the mechanical and hygrothermal performance of the cob, allowing for reduced wall thickness. These findings support the development of eco-friendly, sustainable, and energy-efficient building materials.

This study investigates two ultra-lightweight earth-based composites made from rapeseed straw (RS) and hemp shive (HS) granulates and a binder of raw-earth. An experimental campaign was conducted to evaluate their mechanical strength, hygric behavior, and durability under extreme variations of relative humidity. The raw materials were characterized: two types of raw-earth were analyzed for particle size distribution and mineralogical composition, together with the particle size distribution of plant granulates. Water absorbency of the granulates was measured across time scales from 1 min to 14 days. Several series of test blocks (10 $$\times $$ × 10 $$\times $$ × 10 $$cm^{3}$$ c m 3 ) with varying densities (250–350 $$kg/m^{3}$$ k g / m 3 ) and different water content in the slurry were hand-casted and systematically evaluated. The drying phase, undertaken under free but monitored temperature and relative humidity (T-RH) conditions and measured by weighing, reveals a longer drying time for rapeseed than for hemp based composites.In the first phase, blocks were prepared with varying water content, highlighting that a high water content increases by up to 50% the mechanical strength under uniaxial load. In the second phase, hygric regulation potential was assessed by exposing blocks to extreme relative humidity (RH) (from 20% to 90%) showing that both composites have excellent moisture buffering, with uptake of 14wt.% after 6 days. Finally, durability under repeated RH variations was evaluated using an environmental chamber. Blocks underwent several weeks of cyclic RH changes (20%–95%) before testing for mechanical strength. Slight strength loss were revealed for rapeseed composites. Additionally, earth binders with very high clay content (60% clay) were more susceptible to strength degradation than those with lower clay mineral content (30% clay). The findings highlight the potential of both these sustainable insulation materials for the building sector.

In the context of sustainable construction, the demand for low-carbon building materials has increased interest in raw earth due to its availability and ecological benefits. Bio-based additives such as cellulose fibers and starch are often introduced to enhance mechanical and durability properties, although their impact on hygrothermal performance requires further investigation. This study examined the hygrothermal and mechanical properties of three raw earth adobe brick formulations: a reference sample, one with cellulose fibers, and one with starch. Key properties, including water vapor permeability, thermal conductivity, volumetric heat capacity, moisture buffer value, and elastic modulus, were analyzed. Notably, moisture regulation and air permeability remained excellent across all formulations, with minimal impact from the bio-based additives. These findings underscore the potential of raw earth adobe bricks, with or without bio-based additives, as a viable low-carbon material for sustainable construction.

The evaluation of permanent deformation in soils used as pavement constituents or final layers of earthworks is essential for road and railway design when considering a mechanistic approach to structure design. However, due to environmental concerns, it is increasingly difficult to explore new soil deposits for such works, making the stabilization or reinforcement of materials a viable alternative. In this context, an exploratory assessment was conducted to evaluate the effect of adding piassava fibers to a clayey soil, with characteristics commonly found in subgrade soils in Brazil. Triaxial repeated load tests were performed to evaluate permanent deformation considering two pairs of deviatoric and confining stresses: (210, 70) and (450, 100) kPa, and 100,000 load cycles at a frequency of 5 Hz. The results show that the natural soil exhibits significant permanent deformation when subjected to the highest stress pair, and the simple addition of fibers leads to a significant reduction. With the addition of cement, the total permanent deformation becomes very low, making piassava fiber a promising material for reinforcing pavement or earthworks materials.

Stabilized 3D-printable earth-based building products can be developed by utilizing excavated soil containing non-expansive clays. Further reduction in embodied carbon and improvement in engineering properties can be attained by sequestering carbon dioxide in the 3D-printable materials via accelerated carbon curing (ACC). This research aims to utilize kaolinite-rich lateritic soil as a 25% and 50% replacement of natural sand in 3D-printable formulations and investigate the influence of ACC on compressive strength, shrinkage, and resistance to acid-induced degradation. A combination of Portland cement (OPC) and class F fly ash (FA) have been used as stabilizers, where FA is used to replace 30% of OPC. Experimental findings suggest that a combination of FA and clay (mainly kaolinite) in the used soil imparts improvement in thixotropy by 18–30% and enhances flow retention compared to the control (without soil or FA). Furthermore, the structural build-up after extrusion is enhanced due to the flocculation of clay at rest. As a result, OPC-FA-soil mixes demonstrated substantially better buildability, evident from a printed height of 1.20 m compared to 0.48–0.54 m for OPC-sand (CC0) and OPC-FA-sand (CF30) mixes. The wet compressive strength of the 3D-printed materials is enhanced by 29–47% due to CO2 curing, depending on the loading direction, ascribed to the matrix densification by calcium carbonate crystals Carbon sequestration mitigates the loss in strength and mass of 3D-printed materials by 20–45% after exposure to sulfuric acid (pH of 0.5) for 56 days. This is attributed to reduced porosity and better neutralization capacity of calcium carbonate in low pH environments. In summary, the technology presents a potential pathway to develop low-carbon, durable, and resilient 3D-printed stabilized earth constructions.

The valorization of Excavated Earth (ExE) in concrete production represents a significant opportunity for sustainable construction while aligning with circular economy principles. This review paper explores strategies to reduce Portland cement content in construction materials by incorporating natural fibers, and earthen materials, creating low-carbon, high-performance building products. Natural fibers, such as Miscanthus, Bamboo, and Coconut, offer renewable, CO₂-sequestering solutions. However, they require physical, chemical, or thermal treatments to address challenges such as water absorption and sugar leaching, enhancing their compatibility with concrete matrices. The present review extensively discusses the transition from conventional ordinary Portland cement concrete binders’s formulations to alternatives like bio-based fibers for low-carbon concrete using supplementary cementitious materials SCMs. The review also attempts to explore the importance of the biochemical composition of natural fibers on the performance of bio-based concrete systems. The treatment methods that enhance the behavior and lifetime of fibers are also discussed. Life cycle assessment (LCA) is emphasized as a critical tool for evaluating the environmental impacts of these matrices, optimizing CO₂ fixation, and assessing the recycling potential of end-of-life materials using representative indexes, mostly regarding Global Warming Potential (GWP). Critical questions include: Considering the objective of minimizing CO₂ emissions and the significant environmental impact revealed by life cycle assessment (LCA) for thermal treatments such as calcination for (SCMs) and heat processing for natural fibers, are there alternative methods that can achieve comparable performance with a lower carbon footprint? Research in this domain remains limited, and the review identifies significant gaps. It underscores the role of initiatives like the RECYBEX-3B project supported financially by the Ile-de-France (IdF) region and TRACTEBEL-ENGIE company, which aims to recycle excavated sludge into bio-fiber-reinforced concrete blocks. Finally, the findings propose actionable pathways to advance low-carbon construction technologies, fostering a balance between environmental sustainability and material performance.

To replace the traditional plasterboards used in buildings, earthen panels were developed to meet sustainable development challenges. These panels were designed to limit environmental impacts through several approaches targeting the different stages of a building’s life cycle: limiting embodied energy by using local resources, reducing energy consumption during construction by taking advantage of the hygrothermal properties of the earth, promoting the recyclability by avoiding the use of synthetic stabilizers. These panels are designed to be fixed to timber frames or to the inside of load-bearing walls. An initial laboratory study determined the quantities of components and the optimum implementation to meet the expected specifications. A local resource, Manech sheep’s wool as 20 mm fibre length was added at the rate of 1% by volume to limit the cracking of the panels under flexural stress, especially during handling. These fibres reduce panel brittleness, increase ductility. To avoid the use of synthetic binders, the compaction method is chosen. Full-size panels (60 × 60 cm) were produced in a factory and were characterised to validate their flexural strength, shock resistance and abrasion resistance. Flexural strength reached 0.74 MPa, impact depth 1.21 mm and abrasion coefficient 0.47 g/cm2. The feedback of the industrial scale highlights the challenges of large-scale homogenization and the complexity of achieving an aesthetically pleasing surface finish.

The use of waste materials in masonry mortars is relatively rare, as traditional formulations primarily rely on cement and lime as binders, which are not sustainable in the context of 21st-century sustainable development goals. This study investigates the effects of cement substitution with ceramic waste powder, biomass ash, and fly ash on the restrained shrinkage of masonry mortars. Eight different mortar mixtures were produced, varying the volume ratios of solid components (1:0.7:4.2 and 1:1:4) and cement replacement levels, which reached up to 50%. Compressive strength testing revealed that all mortar types met the requirements for masonry mortars used in structural applications (class M5). After 3 months of exposure to ambient temperature and humidity, specimens were visually inspected for shrinkage-induced cracks. The distribution and width of cracks were recorded, and the pull-off strength was subsequently measured. The results confirmed that both the component volume ratio and the level of cement replacement significantly influenced the appearance and propagation of cracks caused by plastic shrinkage. Notably, some of the supplementary cementitious material (SCM)-blended mortars demonstrated favorable performance, with no visible cracks after 3 months of exposure to shrinkage effects. This study highlights the potential of using waste-based SCMs to improve the shrinkage behavior of masonry mortars, contributing to more sustainable construction practices.

The high consumption of non-renewable resources coupled with the generation of solid waste has been contributing to the search for sustainable materials that can be used in civil construction. Brewer´s spent grain is a by-product generated from the beer production process, formed by the solid part obtained from the wort filtration, before boiling. It is the main by-product of the brewing process and is currently destined for animal feed. The declared beer production volume in Brazil reaches 15.3 billion liters, which represents approximately 3.06 million tons of spent grain. Coating mortars with spent grain in their composition emerge as an alternative to minimize the environmental impact associated with the presence of Portland cement and lime, while improving their hygrothermal properties. Due to its cellular structures, malt bagasse has a high water absorption capacity, which can be used to improve the water retention capacity of the mortar, working as a functional substitute for lime. Thus, this study proposes the development of a coating mortar containing malt bagasse as partial replacement of lime in cement:lime:sand matrices. Mortars with volume substitutions of lime by malt bagasse of 5, 10 and 15% were produced and tested in fresh and hardened state. Results indicate that the direct substitution of lime by malt bagasse led to a decrease in workability, an increase in entrapped air and a decrease in compressive strength. It was concluded that for the proper application of the material, the water absorption capacity of the bagasse must be taken into account during proportioning. The feasibility analysis of using spent grain for the production of cement composites represents an important step towards sustainability in civil construction, offering an innovative and environmentally responsible solution for the use of agro-industrial waste and the reduction of the environmental impact of the construction industry.

This paper reviews the microstructural properties of calcined and uncalcined laterite based-geopolymer binder systems. The properties such as X‐ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier‐Transform Infrared spectroscopy (FTIR), Differential scanning calorimetry coupled with thermogravimetric analysis (DSC/TG), 29Si and 27Al Magic Angle Spinning Nuclear Magnetic Resonance (29Si and 27Al MAS-NMR) spectroscopy, Energy-Dispersive Spectroscopy (EDS) and X-band electron paramagnetic resonance (EPR) spectroscopy are reviewed in this work. The microstructural properties depend on the precursors/ aluminosilicate or starting materials used i.e. laterite, the molar ratio (Si/Al), curing time, curing temperature, alkaline activator types, water content, and the chemical and mineralogical composition of the precursors/ aluminosilicate or starting materials used i.e. laterite. The outcomes from this study revealed the formation of fayalite (FeSiO4) as newly formed phase within the geopolymer samples. This review also demonstrated that there is lack of study in microstructural properties such as DSC/TG, EDS, EPR, 29Si and 27Al MAS-NMR spectroscopy etc. on calcined and uncalcined laterite based-geopolymer binders. XRD studies showed that the main products of alkali activation of the calcined laterite are quartz, ilmenite, hematite and maghemite. Examination of SEM analysis revealed that the geopolymer samples cured at 80 ℃ showed a heterogeneous compact and dense structure resulting from high polycondensation.

Microbial induced calcium carbonate precipitation (MICP) is a novel approach in the field of biocementation that is suitable for use in the construction industry. MICP has various applications which have already been well-researched, such as in soil improvement and self-healing concretes. This study shows an MICP surface treatment method to improve the properties of recycled aggregates. Due to the disadvantageous porosity properties of recycled aggregates, their use in recycled concrete is challenging. MICP treatment forms a calcium carbonate layer on the recycled aggregate’s surface to achieve a sealing effect. However, the MICP process also produces by-products such as ammonium salts which can affect the recycled aggregate concrete’s strength. The type of ammonium salt formed depends on the calcium source used during treatment. The calcium sources tested in the MICP process include: calcium chloride, calcium acetate, and calcium formate. Ammonium is known to decrease the compressive strength of concrete. To investigate this effect in recycled concrete in more detail, the ammonium content of the MICP-treated recycled aggregates was measured using eluate tests. Various rinsing strategies were carried out to examine the ammonium removed from the aggregates and the changes in the resulting compressive strength. The results show that both the ammonium concentration measured in the eluate and the calcium source used during treatment affect the mechanical properties of the concrete. Using an overhead shaker for rinsing was found to be highly effective in removing ammonium, resulting in an increase in the compressive strength of the recycled aggregate concrete.

The cement industry is highly polluting, contributing to the emission of toxic gases. Geopolymer mortar, made from materials rich in aluminum and silicon oxides, emerges as a sustainable alternative, with lower energy consumption and CO2 emissions, helping to reduce carbon footprint in construction industry. This study aims to investigate the influence of curing conditions on the properties of geopolymer mortar. Geopolymer mortar was prepared from metakaolin, as precursor, and sodium hydroxide and silicate, as chemical activators. The molar ratios of Na2O/SiO2, SiO2/Al2O3, Na2O/Al2O3 and H2O/Na2O used in the mixture were 0.26, 3.89, 1.03 and 9.02, respectively. The specimens were cured under two conditions and then subjected to compressive strength, at 3, 7 and 28 days, density, porosity and water absorption tests, at 28 days. Half of the geopolymer specimens were cured in the laboratory room, at ambient temperature of 27 ℃ and humidity of 89%, and the rest were cured in an oven, at 60 ℃ for 24 h, followed by curing in the laboratory room until the tests age. The findings revealed that thermal curing led to an increase in 3 and 7-days compressive strength, when compared with specimens cured at ambient temperature. However, specimens cured in ambient temperature (27 ℃) had the highest compressive strength with 41 MPa, at 28 days. In this study, the density, porosity and water absorption of the specimens cured by two methods were similar. This result demonstrates the effectiveness of curing geopolymer mortar at ambient temperature, highlighting its ability to provide better strength to geopolymer mortar at 28 days of curing.

The research investigated the influence of graphene oxide (GO) addition on cement composites carbonation. Mortar samples were manufactured with Brazilian Cement CP V-ARI, ratio 1:3, with contents of 0%, 0.03% and 0.05% of GO ratio relative to the cement mass. No dispersants were used so that there were no intervening factors in the results of the experiments. Tests were performed on water absorption by immersion, mechanical behavior under compression and tensile stress by splitting tensile test and accelerated carbonation. It was possible to verify that carbonation influences the mechanical behavior of the composites. The addition of 0.05% of GO reduced the compressive strength of the carbonated samples of the mortars subjected to accelerates carbonation when compared to the 0%GO and 0.03%GO samples. Mortars with 0.03%GO and 0.05%GO showed an increase in carbonation depth in relation to the reference. From the test results it can be concluded that the addition of 0.03%GO has the potential to capture CO2 for the production of unreinforced cementitious composites.

This paper investigates the potential of corn straw ash as a supplementary cementitious material (SCM), focusing on its contribution to sustainable civil construction. The ash was characterized using X-ray diffraction (XRD) and X-ray fluorescence (XRF) to analyze its chemical and mineralogical composition, as well as its pozzolanic potential. Mortars incorporating 35% replacement of cement by corn straw ash were compared to reference mortars, with compressive strength and microstructural analyses performed at 28 and 56 days to evaluate the progressive pozzolanic reaction. The results demonstrated that corn straw ash enhances the mechanical performance of mortars, attributed to its role in improving microstructural densification over time. This approach aligns with the principles of the circular economy by repurposing agro-industrial residues, reducing Portland cement usage, and mitigating environmental impacts. The findings highlight the practicality of integrating agricultural waste into cement matrices, supporting more sustainable and efficient construction practices. Beyond mechanical improvements, the research emphasizes the broader significance of using alternative materials to address key challenges in resource efficiency, waste management, and carbon emission reduction within the construction industry. By showcasing the technical and environmental benefits of corn straw ash, this preliminary study advances the development of innovative, sustainable strategies for transforming agricultural waste into valuable resources, offering practical insights into its application potential.

Sugarcane bagasse ash (SCBA) is an agro-industrial byproduct with potential for use as a supplementary cementitious material (SCM) due to its pozzolanic properties, primarily attributed to its high silica and alumina contents. To confirm this pozzolanic potential, the reactivity of the ash must be assessed. Over the years, various methods have been developed to evaluate the chemical activity of SCMs. Recently, the R3 test was proposed as a rapid, relevant, and reliable method for determining the reactivity of these materials. However, as a relatively new technique, data on its application remain limited, especially for biomass ashes. In this context, this study aimed to apply the R3 test to evaluate the reactivity of different SCBAs and correlate the results with the conventional performance index method. Eight ashes were produced under laboratory-controlled conditions, and six residual ashes were collected from a sugar-ethanol mill, totaling fourteen ashes with different carbon and quartz contents. As expected, ashes with higher content of amorphous silica demonstrated greater pozzolanic activity. Carbon-rich ashes exhibited good pozzolanicity according to both performance index and R3 tests, whereas quartz contamination negatively affected reactivity due to its inert nature. Both bound water content and heat release measured in the R3 test showed strong correlations with performance index results (R2 > 0.90), supporting the suitability of the R3 test for assessing SCBA reactivity and suggesting its potential applicability to other biomass ashes. Based on these correlations, minimum requirements for bound water content and heat release have been proposed to classify reactive materials effectively.

Confronting the construction industry’s immense environmental footprint, this study explores a novel pathway to sustainable building materials - transforming industrial byproducts into new binders. The feasibility of utilising wood-wool cement panel manufacturing waste as a partial replacement for conventional cement was investigated. The waste, containing partially hydrated cement dust and wood fibres, is generated during the sanding stage of wood-wool cement panel production - historically discarded but now repurposed as a resource. The binder’s mechanical compressive strength and environmental impact were evaluated by substituting varying amounts of waste with CEM II cement. The findings reveal that a binder with a compressive strength ranging from 4.4 to 34.7 MPa 1 year after making can be developed. The developed binder can be used differently; for example, the binders of CEM II substitution of 20% and lower can be used as self-bearing binders for biocomposite production, and binders with larger substitution rates can be used as low-strength load-bearing binders in applications like lightweight concrete blocks and reinforced concrete frames. Alternatively, all developed materials can be used as rendering material for the interior walls based on compressive strength (CS II-IV) according to EN 998-1. This material could be a cost-effective alternative to conventional building materials, either as a binder or a material itself.

This study investigates lightweight cement-based composites produced with coffee husk (Coffea arabica) residue as a bio-aggregate. The coffee husk was incorporated as a partial substitute (45% in volume) for fine aggregates. Fresh-state properties were analyzed through calorimetric studies, while hardened-state evaluations included mechanical, thermal, and microstructural analyses. Results showed that the lignocellulosic structure of coffee husk delayed cement hydration, which was mitigated by a washing treatment. This treatment significantly reduced extractive content (up to 82%), improving material compatibility with cement matrices. Despite this, the high shrinkage of coffee husk particles led to a weak interfacial adhesion, influencing mechanical properties. The inclusion of metakaolin and fly ash improved thermal performance and reduced clinker consumption. The composites achieved densities between 1281–1339 kg/m3, qualifying them as lightweight materials. Thermal conductivity values ranged from 0.25 to 0.79 W/(m·K), indicating improved insulation potential. Mechanical tests demonstrated compressive strengths of 1.8–2.2 MPa, comparable to other bio-aggregated composites. This research highlights the feasibility of using coffee husk as a sustainable, cost-effective material for lightweight construction applications.

This study explores the potential of stubble waste biochar as a sustainable resource for construction materials, addressing the environmental challenges posed by crop stubble burning. Converting stubble waste into biochar presents a dual opportunity to mitigate air pollution and reduce carbon emissions. This research focuses on the effect of biochar production temperature on its characteristics and cementitious properties. Biochar was produced at varying temperature ranges of 450 ℃ and 550 ℃ under constant pyrolysis conditions, with a residence time of 120 min and a heating rate of 10 ℃/min. A total of five mixes were prepared: one control mix and four biochar-modified mixes with 5% and 10% cement replacement using biochar produced at both temperatures. Comprehensive characterization reveals that higher production temperatures enhance biochar reactivity, increasing its alkalinity and functional group availability, which significantly improve its interaction with cementitious materials. Results indicate that the 550 ℃ biochar at 5% replacement achieved up to a 24.6% increase in compressive strength, a 12.3% improvement in flexural strength, and a 16.5% reduction in water absorption compared to the control mix. These findings demonstrate that biochar produced at 550 ℃ exhibits superior performance, enhancing mechanical properties and promoting better integration within the cement matrix. Additionally, the incorporation of biochar contributes to a reduction in the carbon footprint of construction materials by sequestering carbon and utilizing agricultural waste. The findings underscore the critical role of production temperature in determining biochar’s efficacy as a sustainable and performance-enhancing additive, paving the way for innovative, environmentally conscious construction practices. This work highlights the transformative potential of stubble waste biochar, offering a scalable solution to environmental challenges while advancing sustainable construction materials.

This study explores the incorporation of olive husk, a renewable byproduct of olive oil production, as a sustainable additive in bio-lightweight concrete. Addressing the limitations of raw olive husk in cement-based mortars, both treated and untreated olive husk were introduced at 15% by weight to evaluate their effects on physical, thermal, mechanical, and moisture absorption properties compared to a reference concrete. The results reveal that both treated and untreated olive husk reduce the bulk density of the bio-concrete, increasing porosity by 24% and 26%, respectively. This enhanced porosity significantly improves thermal insulation, with thermal conductivity values of 0.162 W/m·K for untreated samples and 0.692 W/m·K for treated samples. Sorption isotherms indicate that untreated olive husk-based concrete exhibits superior moisture absorption. In contrast, treated olive husk-based samples demonstrate more balanced moisture uptake, offering improved durability under fluctuating humidity conditions. As expected, the inclusion of olive husk results in a reduction in compressive strength, with untreated samples showing a more pronounced decline. Nevertheless, both treated and untreated olive husk maintain acceptable mechanical performance for non-load-bearing applications. Treated olive husk, however, achieves an optimal balance between thermal insulation and mechanical strength, positioning it as a more versatile solution for broader construction use. This research highlights the potential of olive husk, both treated and untreated, as an eco-friendly component in bio-lightweight concrete, contributing to the development of sustainable and thermally efficient building materials.

Biochar has emerged as a promising material for carbon sequestration and decarbonization efforts. By capturing atmospheric CO₂, biochar contributes to reducing greenhouse gas concentrations and enhancing environmental sustainability. Grout, essential in concrete structures, plays a significant role in determining the mechanical and durability properties of concrete. Understanding the impact of biochar on grout can lead to advancements in sustainable construction materials. This study evaluates the effect of incorporating biochar on the fresh and hardened properties of grout, such as flowability, consistency, and compressive strength at 1, 3, 7, and 28 days. Rheological assessments were conducted using tests such as the mini slump test, Lombardi plate test, and Marsh cone flow time, while compressive strength tests were performed to assess mechanical performance. The results indicate that biochar incorporation increases water demand, but this can be effectively mitigated with higher water-to-binder ratios and superplasticizer dosages. Optimized biochar mixes exhibited excellent flowability, with mini slump and Marsh cone values comparable to control mixes. In terms of compressive strength, mixes with moderate biochar replacement (2.5–5%) and proper adjustments in mix design achieved superior performance, with strengths exceeding 100 MPa at 28 days. These findings demonstrate that biochar can enhance grout sustainability without compromising mechanical or fresh properties, paving the way for greener construction materials.

Shrinkage-induced cracking in cementitious systems compromises their lifespan and durability. This study addresses concerns related to dimensional variations by examining the diffusion of cement alternatives, including olive waste ash (OWA)—derived from burning the olive oil extraction residue “pomace”— into mortar and cement paste. A comparative analysis is conducted to assess the impact of various OWA levels (0, 5, 10, 15, and 20%) on distinct volumetric stability parameters, namely chemical, drying, and autogenous shrinkage measured during 28 days. All mixtures are prepared using a water-to-cement ratio of 0.45 and a sand-to-cement ratio of 2 for mortar. The results reveal that OWA serves as a key element in reducing all length change parameters, owing to its content and interactions with other components within the matrix. Additionally, mortar specimens exhibit lower shrinkage values relative to paste specimens. Furthermore, the strong correlations between the shrinkage behavior of OWA-based paste and mortar demonstrate that paste performance reliably predicts mortar performance. This paper endeavors to provide valuable insights into the similarities and differences in shrinkage performance of paste and mortar across various OWA levels, optimizing its usage for better sustainable applications.