Search Results (178)

To promote the large-scale utilization of construction and industrial solid waste in engineering, this study focuses on developing accurate prediction and optimization methods for the unconfined compressive strength (UCS) of composite recycled mortar. Innovatively incorporating three types of recycled powder (RP)—recycled clay brick powder (RCBS), recycled concrete powder (RCBP), and recycled gypsum powder (RCGP)—we systematically investigated the effects of RP type, replacement rate, and curing period on mortar UCS. The core objective and novelty lie in establishing and comparing three artificial intelligence models for high-precision UCS prediction. Furthermore, leveraging GA-BP’s functional extremum optimization theory, we determined the optimal UCS alongside its corresponding mix proportion and curing scheme, with experimental validation of the solution reliability. Key findings include the following: (1) Increasing total RP content significantly reduces mortar UCS; the maximum UCS is achieved with a 1:1 blend ratio of RCBP:RCGP, while a 20% RCBS replacement rate and extended curing periods markedly enhance strength. (2) Among the prediction models, GA-BP demonstrates superior performance, significantly outperforming BP models with both single and double hidden layer. (3) The functional extremum optimization results exhibit high consistency with experimental validation, showing a relative error below 10%, confirming the method’s effectiveness and engineering applicability. Full article

This study investigates the bond behavior of fabric-reinforced cementitious matrix (FRCM) composites with three common masonry substrates—solid clay bricks (SBs), perforated bricks (PBs), and concrete hollow blocks (HBs)—using knitted polyester grille (KPG) fabric. Through uniaxial tensile tests of the KPG fabric and FRCM system, along with single-lap and double-lap shear tests, the interfacial debonding modes, load-slip responses, and composite utilization ratio were evaluated. Key findings reveal that (i) SB and HB substrates predominantly exhibited fabric slippage (FS) or matrix–fabric (MF) debonding, while PB substrates consistently failed at the matrix–substrate (MS) interface, due to their smooth surface texture. (ii) Prism specimens with mortar joints showed enhanced interfacial friction, leading to higher load fluctuations compared to brick units. PB substrates demonstrated the lowest peak stress (69.64–74.33 MPa), while SB and HB achieved comparable peak stresses (133.91–155.95 MPa). (iii) The FRCM system only achieved a utilization rate of 12–30% in fabric and reinforcement systems. The debonding failure at the matrix–substrate interface is one of the reasons that cannot be ignored, and exploring methods to improve the bonding performance between the matrix–substrate interface is the next research direction. HB bricks have excellent bonding properties, and it is recommended to prioritize their use in retrofit applications, followed by SB bricks. These findings provide insights into optimizing the application of FRCM reinforcement systems in masonry structures. Full article

This study presents a comprehensive non-destructive evaluation of a broad range of construction materials using the impulse excitation of vibration (IEV) technique. Tested specimens included low- and normal-strength concrete, fiber-reinforced concrete (with basalt, polypropylene, and glass fibers), lime mortars (NHL-2 and -3.5), plaster, and clay bricks (light and dark). Compressive and flexural strength tests complemented dynamic resonance testing on the same samples to ensure full mechanical characterization. Flexural and torsional resonance frequencies were used to calculate dynamic elastic modulus, shear modulus, and Poisson’s ratio. Strong correlations were observed between dynamic elastic modulus and shear modulus, supporting the compatibility of dynamic results with the classical elasticity theory. Flexural frequencies were more sensitive to material differences than torsional ones. Fiber additives, particularly basalt and polypropylene, significantly improved dynamic stiffness, increasing the dynamic elastic modulus/compressive strength ratio by up to 23%. In contrast, normal-strength concrete exhibited limited stiffness improvement despite higher strength. These findings highlight the reliability of IEV in mechanical properties across diverse material types and provide comparative reference data for concrete and masonry applications. Full article

Historical masonry structures deteriorate over time, requiring restoration and strengthening. Hydraulic lime-based mortars (HLMs), due to their compatibility with historical materials, are commonly used for this purpose. This study examines the fire resistance of masonry walls constructed with HLMs. Masonry prisms with clay bricks were prepared using HLMs in accordance with material testing standards. Specimens were subjected to high temperatures ranging from 200 °C to 800 °C, followed by flexural–compression tests for mortar and compression tests for masonry prisms. A total of 20 masonry prism specimens, 15 brick specimens, and 15 mortar specimens were tested, including reference specimens at room temperature. Experimental results indicate that masonry prisms, clay bricks, and HLMs progressively lose their mechanical properties as temperature increases. The elastic modulus of masonry prisms was evaluated according to relevant standards, and Finite Element Analysis (FEA) was conducted to validate temperature-dependent material properties. The stress–strain response of M15 HLM masonry prisms was determined, addressing the absence of such data in EN 1996-1-2. Additionally, compression test results were compared with digital image correlation (DIC) analyses to enhance measurement accuracy. This study provides critical insights into the thermal performance of masonry walls with HLMs, contributing to the development of fire-resistant restoration materials. Full article

This study elucidates the photocatalytic NOx abatement efficacy of eco-efficient mortars incorporating construction waste-derived aggregates functionalized with nano-TiO₂. The research findings demonstrate a positive correlation between NOx abatement efficiency and nano-TiO₂ substitution ratio, with recycled glass sand (RG)-based panels exhibiting superior performance compared to standard sand and recycled clay brick sand (RCBS)-based counterparts. The employment of ultrasonic dispersion as a nano-TiO₂ incorporation method yields enhanced abatement efficiency relative to direct mixing, attributable to improved photocatalyst dispersion and surface area accessibility. The loading capacity of nano-TiO₂ on recycled aggregates is observed to be positively influenced by the concentration of nano-TiO₂ solution, with recycled clay brick sand demonstrating the highest loading capacity. RG-RCBS panels are shown to exhibit higher NOx abatement efficiency than standard sand (SS)-RCBS panels, with an optimal substitution ratio of 40% glass sand identified for maximizing abatement efficacy in RG-RCBS systems. A decline in NOx abatement efficiency is observed with increasing NOx flow rate and concentration, attributable to reduced pollutant residence time and excess pollutant load exceeding the panels’ processing capacity. Prolonged curing time also results in diminished abatement efficiency, due to microstructural alterations within the mortar matrix and the accumulation of photocatalytic reaction byproducts. Collectively, these findings underscore the potential of recycled aggregate-based mortars, in conjunction with nano-TiO₂, as a viable eco-efficient strategy for NOx abatement, highlighting the critical influence of material selection, photocatalyst loading, and operational parameters on system performance. Full article

Mortar is widely used in civil construction. The inclusion of expanded clay as a lightweight aggregate reduces the density of mortar, enabling lighter structural elements and potentially lowering material and energy requirements during construction. This research aims to produce lightweight mortars by partially replacing fine aggregate with proportions of expanded clay. Six mortar formulations were prepared with varying proportions of expanded clay. The constituent materials of the mixtures and the mortars were characterized according to regulatory prescriptions. The results indicated that the increase in the replacement of fine aggregate with expanded clay reduced the consistency and density of the mass in the fresh state. No significant differences were observed in water absorption by immersion among the mortars in the hardened state. Regarding mechanical tests, most mortars’ tensile strength in bending remained stable. On the other hand, compressive strength decreased. The tensile adhesion was also reduced with the incorporation of expanded clay. After exposure to sodium sulfate solution, all tensile strength results in bending improved. The coefficient of the constructive quality indicated that the ideal replacement formulation is 20% expanded clay. These mortars represent a viable technical alternative, complying with current standards and contributing more efficiently and sustainably to civil construction. Full article

The construction industry’s escalating environmental footprint, coupled with the underutilization of construction waste streams, necessitates innovative approaches to sustainable material design. This study investigates the dual functionality of recycled clay brick powder (RCBP) as both a supplementary cementitious material (SCM) and an alkali–silica reaction (ASR) inhibitor in hybrid mortar systems incorporating recycled glass (RG) and recycled clay brick (RCB) aggregates. Leveraging the pozzolanic activity of RCBP’s residual aluminosilicate phases, the research quantifies its influence on mortar durability and mechanical performance under varying substitution scenarios. Experimental findings reveal a nonlinear relationship between RCBP dosage and mortar properties. A 30% cement replacement with RCBP yields a 28-day activity index of 96.95%, confirming significant pozzolanic contributions. Critically, RCBP substitution ≥20% effectively mitigates ASRs induced by RG aggregates, with optimal suppression observed at 25% replacement. This threshold aligns with microstructural analyses showing RCBP’s Al³⁺ ions preferentially reacting with alkali hydroxides to form non-expansive gels, reducing pore solution pH and silica dissolution rates. Mechanical characterization reveals trade-offs between workability and strength development. Increasing RCBP substitution decreases mortar consistency and fluidity, which is more pronounced in RG-RCBS blends due to glass aggregates’ smooth texture. Compressively, both SS-RCBS and RG-RCBS mortars exhibit strength reduction with higher RCBP content, yet all specimens show accelerated compressive strength gain relative to flexural strength over curing time. Notably, 28-day water absorption increases with RCBP substitution, correlating with microstructural porosity modifications. These findings position recycled construction wastes and glass as valuable resources in circular economy frameworks, offering municipalities a pathway to meet recycled content mandates without sacrificing structural integrity. The study underscores the importance of waste synergy in advancing sustainable mortar technology, with implications for net-zero building practices and industrial waste valorization. Full article

Global cement manufacturing generated 1.6 billion metric tons of CO₂ in 2022 and relies heavily on non-renewable raw materials. Utilizing agro-industrial waste as supplementary cementitious material (SCM) can help mitigate the demand for these resources. SCMs have been integrated into cement production to deliver both technical and environmental benefits to mortars and concrete. This study examines mortar blends containing blast furnace slag (BFS), Brazilian calcined clay (BCC), and bamboo leaf ash (BLA). While BFS and BCC are already established in the cement industry, recent research has highlighted BLA as a promising pozzolanic material. The SCMs were characterized, and mortars were produced to assess their flexural and compressive strength, as well as durability indicators such as electrical resistivity, chloride diffusion, migration coefficient, and carbonation resistance. The findings reveal significant performance enhancements. Partial cement replacement (20% and 40%) maintained the strength of both binary and ternary mortars, demonstrating statistical equivalence to the reference mortar (p > 0.05). It also contributed to an improved pore structure, reducing the migration coefficient by up to four times in the 20BLA20BCC mix (which replaces 20% of cement with BLA and 20% with BCC) compared to the reference mix. Chemically, the SCMs enhanced the chloride-binding capacity of the cementitious matrix by up to seven times in the case of the 20BCC mortar, thereby improving its durability. Therefore, all tested compositions—binary and ternary—showed mechanical and durability advantages over the reference while also contributing to the reduction in environmental impacts associated with the cement industry. Full article

The challenge of thermally upgrading traditional stone masonry buildings is addressed through the analysis of a representative example typical of regional rural architecture in central Poland, constructed using soft silica limestone and clay mortar. These buildings, which form an important part of the local cultural heritage, are increasingly becoming the subject of interdisciplinary research and conservation initiatives. This study presents a detailed characterization of the materials and architectural features specific to this building typology. Thermal transmittance calculations were performed and analyzed, with the use of THERM 7.6.1.0 software enabling precise modeling of the wall’s heterogeneous structure. The physical and thermal properties of natural materials—particularly soft silica limestone and clay—were taken into account. The analysis included evaluation of the heat transfer coefficient, temperature distribution, and heat flux density for a reference wall model, as well as for variants with both internal and external insulation layers. The study explores thermal comfort and energy performance within the broader context of preserving and reusing historic rural buildings. Furthermore, the findings are discussed in relation to current European energy efficiency regulations and heritage protection frameworks. The scientific value of this work lies in its context-specific, material-sensitive methodology and in providing practical insight into balancing energy retrofitting with architectural conservation. Full article

The elastic modulus is one of the fundamental parameters controlling the mechanical behaviour of concrete. In this study, the Movable Cellular Automata (MCA) method is applied to predict the Young’s modulus of concrete based on the properties of its components. Each automaton represents one component: cement paste, fine aggregate, or coarse aggregate. A parametric sensitivity analysis was performed using Grey System Theory (GST) on hypothetical concrete modeled with the MCA method. The analysis showed that the coarse aggregate type, coarse aggregate-to-total aggregate ratio, and water-to-cement ratio have the greatest impact on the Young’s modulus. To test the effectiveness of the MCA method in modelling concrete, results of numerical simulations were compared with experimental data available in the literature. The first numerical simulations were conducted for mortars containing cement paste and sand as well as for concretes produced by adding granite to them. Two approaches were used to perform the simulations; in the first approach, a sample contained automata representing cement paste, sand, and granite, while in the second the automata represented mortar and granite. High consistency was achieved, with results from both approaches differing by only 0.6%. Subsequent simulations focused on concretes with different water-to-cement ratios (0.45, 0.55, and 0.65), the origin of the basaltic aggregate, and various aggregate contents (60%, 54%, 48%, and 42%). Results showed high agreement between simulations and experimental data, confirmed by a high coefficient of determination R² of 0.84 and mean squared error of 2.43 GPa². Finally, simulations were performed for lightweight expanded clay aggregate concrete, resulting in an R² of 0.86 and mean squared error of 0.81 GPa², which demonstrates the effectiveness of the MCA method in predicting the static elastic modulus of concrete. Full article

The use of recycled burnt clay brick sand (RBS) and recycled concrete sand (RCS) in historical lime-based repair mortars can reduce the environmental impact caused by construction and demolition waste disposal. This study examined the use of fine recycled concrete and recycled brick aggregates for the production of historical repair mortars using hydraulic lime binder and the influence of the resulting mortars on the performance of historical buildings in reduced scale walls (stacks). Natural-river-sand mortar (NSM) was used as control. Results showed that the recycled-burnt-brick-sand mortar (RBSM) performed better in terms of strength compared to the recycled-concrete sand (RCSM) and the NSM mortars. At the age of 7 and 28 days, the flexural strength of the RBSM and the RCSM was 131% and 44%, respectively, and 300% and 68% above that of the control mortar. The 45-day flexural strength of the NSM and RCSM was similar whilst the RBSM mortar’s strength was 177% higher. The compressive strength followed similar trend. On the other hand, the strength and modulus of elasticity of the stacks were found to be largely influenced by the strength of the brick units. Full article

This work explores issues related to traditional heritage, its evolution, and its transmission within construction practices. It focuses on a case study concerning the reintroduction in Tamentit, an oasis in southwestern Algeria, of a nearly forgotten construction technique: the use of a local stone known as “Agharf”, composed of saline pebbles, bound or assembled with a clay mortar enriched with salt, allowing the construction of robust structures adapted to their environment. Traditionally used in certain specific areas of the Sahara, it was notably employed in isolated regions such as Siwa in Egypt. After a long period of disuse, this technique is experiencing a renewed interest and appears to be gradually reintegrating into the local practices of artisans. This raises several questions: What justifies the return of this technique? What role does contemporary society assign to it, and what actions are being taken to ensure its sustainability? Fieldwork, consisting of on-site observations and semi-structured interviews with artisans and master artisans, the ma‘alem, was conducted to analyze their perception of this heritage, to understand the tangible and intangible aspects of the construction process, and to explore the challenges related to its transmission. The interviews reveal that, despite the challenges and reservations expressed by the community, the Agharf remains for the artisans a symbol of identity and craftsmanship, far from being a lost intangible heritage. The conditions and benefits of its use are also discussed. Full article

With the increasing demand for lithium resources and the enhancement of global environmental awareness, how to efficiently and environmentally develop clay-type lithium resources is of great strategic significance for future development. Clay-type lithium slag (LS) is a byproduct resulting from the extraction of lithium from clay-type lithium ores. Its primary chemical constituents include SiO₂ and Al₂O₃, and it exhibits potential pozzolanic properties. Clay-type lithium ore is of low grade, so a large amount of clay-type LS is produced during its production. In this study, calcined clay-type LS, limestone powder (LP), and cement clinker were used as the main raw materials to prepare low-carbon LC³ cementitious materials. The study focused on the effect of clay-type LS and LP on the new mixing properties, mechanical properties, hydration kinetics, and microstructure formation and transformation of the cementitious materials. The findings revealed that incorporating clay-type LS and LP significantly raised the standard consistency water demand of cement and reduced the setting time of the binding material. While clay-type LS and LP initially weakened the mechanical performance of the cement mortar, it enhanced these properties in the later stages. The compressive strength of LC-10 and LC-20 at 180 days exceeded that of the reference by 3.7% and 1.1%, respectively. In addition, the number of micropores between 3 and 20 nm in LC³ cement increased significantly. It showed that the addition of clay-type LS and LP could optimize the pore structure to some extent. According to research, the optimal content of clay-type LS and LP should not exceed 30%. This method not only consumes the solid waste of clay-type LS, but also facilitates the green and low-carbon transformation of the cement industry. Full article

Recent studies have shown the viability of low-grade calcined clays as a partial substitute for cement in construction applications. However, there is limited information about the performance of low-grade calcined clay in withstanding chloride-rich environments. This paper investigates the durability performance of mortar prepared by partially substituting cement with low-grade calcined clay. Naturally occurring clay having a kaolinite content of 17% was calcined at 900 °C, blended and used to prepare composite cement samples containing up to 40% by weight low-grade calcined clay. Durability studies were conducted using the rapid chloride penetration test (RCPT), freeze and thaw, sorptivity, permeable porosity, ultrasonic pulse velocity (UPV), and autogenous shrinkage. The incorporation of calcined clay resulted in significant improvements in durability properties, including reductions in sorptivity, permeable porosity, and chloride ion penetration. Additionally, enhanced freeze–thaw resistance was observed, indicating the ability of calcined clays to mitigate deterioration under harsh environmental conditions. These improvements in durability translate to extended service life and reduced maintenance requirements for concrete structures. Full article

This paper reviews the performance of low-grade calcined clay as a partial substitute for Portland cement in concrete, emphasizing its potential to enhance sustainability in construction. Thermal treatment of naturally occurring clays at optimal temperatures produces amorphous siliceous materials with pozzolanic properties. Clays with substantial kaolinite content exhibit significant pozzolanic reactivity when calcined at temperatures between 700 and 850 °C, with effective firing possible up to 1000 °C. Research shows that replacing Portland cement with calcined clays improves the mechanical and durability properties of concrete, with replacement levels ranging from 10% to 60%, depending on factors such as chemical composition, mineralogy, and reactivity. This paper synthesizes recent findings on low-grade calcined clays with 60–80% purity, which are more abundant, cost-effective, and easier to produce, particularly in developing regions lacking the resources and technology to process high-purity clays (>95% purity). Key aspects explored include calcination methods, optimal firing temperatures, and their effects on particle size distribution and pozzolanic activity. This study also examines the impact of low-grade calcined clay on fresh and hardened concrete and the durability properties of concrete and mortar. By providing a comprehensive analysis, this review highlights the potential of low-grade calcined clays to contribute to more sustainable and durable concrete production, emphasizing the need to optimize calcination processes and fully harness their pozzolanic properties. Full article