Search Results (177)

Sheep wool is a low-value agricultural by-product with potential to contribute to more sustainable cementitious materials. This study investigates Segureña sheep wool fibres as reinforcement in cement mortars, comparing washed wool (W) and cement-encapsulated wool (E) at the same oven-dry raw wool dosages (0.5, 1.0, and 3.0 g per batch), and benchmarking against polypropylene (PP) fibres. Flexural and compressive strength were evaluated at 1, 7, and 28 days, whereas apparent density, water absorption, and thermal conductivity were assessed at 28 days. An intermediate dosage (1.0 g per batch) provided the most favourable mechanical response, while the highest dosage (3.0 g per batch) reduced performance, plausibly due to dispersion limitations and void formation. At 28 days, W-1 reached 9.65 ± 0.50 MPa in flexure (very close to PP-1) and 59.70 ± 1.05 MPa in compression, exceeding PP-1 in compression. Wool incorporation also reduced apparent density and yielded an observed reduction in thermal conductivity of up to ~18% at the highest dosage (single specimen per series). Overall, optimally dosed washed wool can deliver competitive mechanical performance while improving thermal behaviour, supporting circular-economy valorisation of waste wool in eco-mortars. Full article

This work contributes to reinforcing cork-based mortar, with the potential of developing a new eco-friendly lightweight mortar for specific structural applications. Thirteen lightweight mortars were produced by adding cork aggregates (CAs) at fractions of 0.30%, 0.60%, and 0.90% of mortar weight. For each level of CA content, three volume fractions of polyethylene fibers (PFs) were added: 0.25%, 0.50%, and 0.75%. The results indicate that lightening mortar with CA considerably reduces its workability, density, mechanical strengths, and thermal conductivity, as well as increasing its porosity. However, adding PFs to the matrix significantly improves the mortar’s flexural strength by up to 26% and reduces its cracking and brittleness. The 28-day compressive strengths of all mortars remain higher than 15 MPa and can be used in the production of structural elements, according to the RILEM recommendations. The thermal conductivity and dry density decreased, respectively, from 1.73 W/m·K and 2050 kg/m³ for the control mixture to 0.73 W/m·K and 1583 kg/m³ for mortar with 0.90% CA and 0.75% PF. The combination of up to 0.90% CA with 0.75% PF demonstrates satisfactory mechanical and thermal properties and is strongly recommended for use in construction across numerous types of mortar, such as screed mortar for repair and flooring. Full article

The disposal of industrial waste poses a significant environmental challenge, often leading to pollution and degradation of surrounding and terrestrial ecosystems. This study investigates the sustainable valorization of such wastes through the development of one-part geopolymer mortars. Solid sodium silicate was employed as a dry alkali activator for binary blends comprising ground granulated blast-furnace slag (GGBS), clay brick powder (CBP), steel slag (SS), and fly ash (FA), with all mixtures cured under ambient conditions. The mortars were evaluated in terms of fresh properties (flow and setting time) and hardened characteristics, including compressive strength, density, water absorption, and porosity. Durability performance was assessed through mass loss, visual degradation, and compressive strength retention following exposure to acidic (H₂SO₄, HCl) and sulfate environments. Microstructural characterization using XRD, SEM, and FTIR provided insight into the mechanisms of gel formation and degradation in aggressive media. The results revealed that incorporating 5% FA into GGBS-based mortars enhanced 28-day compressive strength by 21.7% compared with the control mix. The inclusion of industrial by-products promoted the formation of C–S–H and C–(A)–S–H gels, contributing to a denser and more refined microstructure. Overall, the findings demonstrate that one-part geopolymer mortars offer a promising, eco-efficient, and durable alternative to traditional cementitious systems, while also addressing safety and handling concerns associated with liquid alkaline activators used in conventional two-part geopolymer formulations. Full article

The re-valorisation of oyster-shell waste offers a sustainable pathway for producing eco-efficient construction materials. This study investigates the physical, mechanical, and durability performance of natural hydraulic lime (NHL) mortars incorporating oyster shells (OSs), applied to solid bricks representative of historical masonry. Two formulations were developed: one with 24% replacement of NHL by oyster-shell powder (OSP, <150 µm) and another with 30% substitution of sand by oyster-shell aggregate (OSA, 0–4 mm), both compared with a control mortar. Mortars were tested in standard molds and directly applied to bricks, including under accelerated aging conditions (temperature and humidity cycles). Results revealed that shell-incorporated mortars applied to bricks exhibited higher bulk density and compressive strength, and lower porosity, capillary water absorption, and water vapor permeability, compared with mold-cast samples. The performance for the shell-based mortars highlights the substrate–mortar interaction, consistent with the behavior of traditional lime-based systems, and the microscope characterization (poro-Hg and X-ray tomography). Shell-incorporated mortars retained stable properties after aging, with variations below 10% compared to unaged mortars. These findings demonstrate the feasibility of oyster shells as partial replacements for lime and sand, confirming its potential as an eco-efficient strategy for sustainable mortars in conserving and rehabilitating historic masonry buildings. Full article

In the background of sustainable development in the construction industry, recycled cement mortar (RCM) has emerged as a research hotspot due to its eco-friendly features, where mechanical properties serve as critical indicators for evaluating its engineering applicability. This study proposes an artificial neural network (ANN) model optimized by intelligent algorithms, including the GWO (grey wolf optimizer), PSO (particle swarm optimization), and a GA (genetic algorithm), to predict the compressive strength of recycled mortar. By integrating experimental and prediction data, we establish a comprehensive database with eight input variables, including the water–cement ratio (W/C), cement–sand ratio (C/S), fly ash content (FA), aggregate replacement rate (ARR), and curing age. The predictive performance of neural network models with different database sizes (database 1: experimental data of RCM; database 2: experimental data of RCM and ordinary mortar; database 3: model prediction data of RCM, experimental data of RCM, and ordinary mortar) is analyzed. The results show that the intelligent optimization algorithms significantly enhance the predictive performance of the ANN model. Among them, the PSO-ANN model demonstrates optimal performance, with R² = 0.92, MSE = 0.007, and MAE = 0.0632, followed by the GA-ANN model and the GWO-ANN model. SHAP analysis reveals that the W/C, C/S, and curing age are the key variables influencing the compression strength. Furthermore, the size of the dataset does not significantly influence the computation time for the above models but is primarily governed by the complexity of the optimization algorithms. This study provides an efficient data-driven method for the mix design of RCM and a theoretical support for its engineering applications. Full article

In this work, a complex and eco-friendly biomass raffinose monomer-modified polycarboxylate superplasticizer (RAF-PCE) was designed and synthesized via the free radical polymerization technique to simultaneously improve paste fluidity and delay fluidity loss in concrete applications. The adsorption, fluidity, and early hydration behaviors of cementitious systems after the introduction of RAF-PCE have been systematically investigated. Experimental results demonstrate that the hydroxy group in raffinose promotes the adsorption of RAF-PCE on the cement particles, thereby elevating the dispersion characteristic of cement paste through electrostatic repulsion, enabling excellent initial fluidity (310 mm). Additionally, its steric hindrance effect has also been identified to play a role in improving paste fluidity and reducing the slump loss of cement slurry. Detailed analyses unveil that RAF-PCE can reduce the concentration of free Ca²⁺ in the pore solution through complexation with Ca²⁺, which prevents the early precipitation of hydration products and realizes a delayed effect on cement hydration, ultimately evolving into a homogeneous and compact microstructure for superior compressive tensile strength of the cement mortar. The 28-day compressive strength of cement incorporating RAF-PCE reached 79.2 MPa, representing a 5.5% enhancement over conventional PCE systems. Our work provides novel insights into the promotion of innovative and green development in the concrete industry by utilizing renewable biomass resources for high-performance materials. Full article

This study investigates the potential of producing zero-clinker, alkali-activated binders and concrete entirely from industrial by-products—ladle furnace slag (LFS), coal ash (CA), and cement kiln dust (CKD). The incorporation of CKD enhanced the workability and compressive strength properties of the alkali-activated mixtures, with the highest mechanical properties at 20% CKD addition. XRD, FTIR, and SEM analyses confirmed the formation of hydrocalumite, indicating improved hydration and microstructural densification. Mortar and concrete produced using the eco-cement reached 28-day strengths of 34.5 MPa and 32.6 MPa, corresponding to concrete class C20/25. These findings demonstrate the feasibility of manufacturing 100% waste-based construction materials suitable for sustainable, non-reinforced applications. Full article

This study investigates a comprehensive study on the mechanical and microstructural behavior of cementitious mortars modified with a combination of internal carbonation (via solid CO₂), calcined clay as a ceramic pozzolanic additive, and bio-based sheep wool fibers. The investigation aimed to explore sustainable routes for enhancing mortar performance while reducing the environmental impact of cement production. A series of mortars incorporating various combinations of dry ice, calcined clay, and wool fibers was prepared and tested to evaluate compressive and flexural strength, porosity, pore size distribution, phase composition, and microstructural morphology. Results demonstrated that internal carbonation significantly promoted matrix densification and compressive strength, increasing fc by approximately 8% compared to the reference. The addition of calcined clay further improved microstructural compactness, reducing total pore volume by 12%, while the incorporation of wool fibers enhanced post-cracking toughness by over 40% despite a 15–30% decrease in compressive strength. SEM and TGA confirmed the formation of calcite and reduced portlandite content, consistent with carbonation and pozzolanic reactions. The findings underscore the potential and limitations of multicomponent eco-modified cement mortars. Optimizing the balance between internal carbonation, pozzolanic reaction, and fiber stability is a key to developing next-generation low-carbon composites suitable for durable and resilient construction applications. Full article

Using almond shell biomass ash (ABA) as a potassium alkaline source and rice husk ash (RHA) as a soluble silica source to produce blast furnace slag (BFS)-based alkali-activated mortars offers a sustainable alternative to commercial activators. However, some thermal treatment is often needed to enhance ash dissolution, potentially increasing the CO₂ footprint. In this study, we evaluated how a low-CO₂-footprint thermal treatment for dissolving ABA, as well as RHA combined with ABA, affects the strength performance of binary (ABA/BFS) and ternary (RHA/ABA/BFS) alkali-activated mortars. This thermal treatment involved mixing the biomasses with hot water (85 °C) in a thermally insulated bottle (TIB). The binary alkali-activated mortar, cured for 7 days in a thermal bath at 65 °C, achieved 58.0 MPa in compressive strength, applying 1-h dissolution of ABA in a TIB. Additionally, the previous dissolution of RHA in conjunction with ABA for ternary alkali-activated mortar, cured also for 7 days in a thermal bath at 65 °C, resulted in mortars with a higher compressive strength, achieving 64.7 MPa. With the prior biomass dissolution method, the binary and ternary alkali-activated mortars cured at room temperature (20 °C) showed compressive strengths of 54.7 and 67.0 MPa after 28 curing days, respectively. Moreover, after 135 curing days, these mortars reached a compressive strength of 61.4 and 71.9 MPa, respectively. The BFS-alkali-activated binders with ABA and ABA plus RHA cut CO₂ emissions by 86.8% and 85.7% compared to the OPC-based binder, respectively. Full article

Newly developed polymer-based grinding chemicals demonstrate superior dispersion, grinding, and strength outcomes compared to traditional amine-based additives. This study provides a comprehensive analysis of the mechanisms underlying the improved performance of polymers in the grinding process. It examines the influence of polymer-based grinding aids (A1-A2-A3) on the hydrophobicity and rheological behavior of CEM I 42.5 R Portland cement. A systematic analysis was conducted using six different grinding aids, comprising three synthesized polycarboxylate ether (PCE)-based polymers and three commercial amine group products. Key properties, including surface tension, hydrophobicity (water contact angle, WCA), slump flow, FT-IR, and rheological parameters, were evaluated. Among the compounds tested, the A2 polymer exhibited the most favorable performance, achieving a high contact angle (131.7°), low surface tension (56.7 dyn/cm), and enhanced mortar fluidity (25 cm slump flow). FT-IR spectroscopy confirmed strong interactions between A2 and cement particles, particularly in the CH₃ bonding regions. Rheological analyses further revealed that A2—2.5 g significantly decreased viscosity and improved shear stress response, indicating superior dispersion and water reduction capability. The findings highlight A2 as a promising eco-efficient additive for enhancing the efficiency, performance, and workability of cementitious systems through polymer-based grinding technology. Full article

The growing demand for eco-efficient construction materials has driven the development of low-clinker cement systems incorporating recycled mineral additives. Finely ground brick powder represents one of such materials with high pozzolanic potential. This article presents an experimental study on the effect of partially replacing slag cement CEM III and ordinary rapid-hardening cement CEM I with brick powder waste of different chemical compositions and fineness levels (63, 32, and 15 µm) on the physical and mechanical properties of blended cement mortars. Compressive and flexural strengths were determined at 2, 7, and 28 days, along with the strength activity index (SAI). Additionally, the setting times and standard consistency were investigated, with the latter showing a correlation with the workability of fresh mortars. Comprehensive microstructural analysis (TGA, SEM, EDX) confirmed the pozzolanic activity of the brick powder, which was manifested by the formation of C-S-H and C-A-S-H phases. The highest strength characteristics were achieved with a 15% replacement of cement by brick powder with a fineness of 32 μm and an increased SiO₂ content (63.06%). Comparative analysis with fly ash- and silica fume-modified mortars revealed that brick powder exhibits comparable performance, confirming its suitability as an active mineral additive. Full article

Artificial aggregates (AAs) are man-made construction materials, and their properties greatly depend on their manufacturing process (e.g., granulation and hardening) and the raw materials used. The conducted research aimed to determine the most advantageous composition of artificial aggregates prepared based on three wastes simultaneously: municipal waste incineration ash (MWIA), sediment from the bottom of a water reservoir (SBWR), recycled cement mortar (RCM)- which was the main waste. A production process of such aggregates was also developed, with the setting of the hardening temperature (20 °C, 200 °C, 400 °C). The X-ray diffractometry (XRD), differential thermal analysis (DTA), and thermogravimetry analysis (TGA) were used to characterize the waste. Then, the properties of cementitious composites prepared with artificial aggregate with the best strength parameters of 0–100% of the natural aggregate were determined. Carbon footprint calculations were performed for the production of artificial aggregate, depending on its composition and for cementitious composites. Full article

The conversion of rough marble blocks into building products is environmentally intensive in terms of energy and water consumption and the generation of solid fragments and marble sludge (MS). This LCA study evaluates the environmental impact of two marble processing plants (for sawing and cutting) with respect to alternative scenarios of MS management including its (a) land disposal (baseline scenario—BS), (b) land disposal after filter pressing (current scenario—CS) and (c) partial valorization in cement mortars associated with the application of solar energy (eco-friendly scenario—ES). In this context, a “gate-to-gate” methodology is applied, while three main steps are considered: the sawing and cutting of marble blocks (main process) and the MS disposal and reuse. The LCA results indicate that terrestrial acidification (TAP), freshwater eutrophication (FEP), climate change and ozone depletion decreased by 10.8 to 37.1% by the adaptation of the BS and by 18 to 38.2% by the adaptation of the ES. At the same time, cumulative energy demand increases by 25.3% and 28.9%, respectively. The contribution analysis showed that the main process has the dominant effect on the examined categories. The contribution of the disposal step on TAP and FEP decreased by 61.6% and 47.9% via the application of the valorization technique. Full article

Cold-bonded (CB) fly ash aggregate, an eco-friendly material derived from industrial by-products, is used to fully replace natural coarse aggregate in producing lightweight concrete (LWC-CB). This study systematically investigates the post-high-temperature mechanical properties and damage mechanisms of LWC-CB. Specimens exposed to ambient temperature (10 °C) and elevated temperatures (200 °C, 400 °C, 600 °C) underwent cubic compression tests, with surface deformation monitored via digital image correlation (DIC). Experimental results indicate that the strength retention of LWC-CB is approximately 6% superior to ordinary concrete below 500 °C, beyond which its performance converges. Damage analysis reveals a transition in failure mode: at ambient temperature, shear failure is governed by the low intrinsic strength of CB aggregates, while after high-temperature exposure, damage localizes within the mortar and the interfacial transition zone (ITZ) due to mortar micro-cracking and thermal mismatch. To elucidate these mechanisms, a three-dimensional mesoscale model was developed and validated, effectively characterizing the internal multiphase structure at room temperature. Furthermore, a homogenization model was established to analyze the macroscopic thermo-mechanical response. The numerical simulations show strong agreement with experimental data, with a maximum deviation of 15% at 10 °C and 3% after high-temperature exposure, confirming the model’s accuracy in capturing the performance evolution of LWC-CB. Full article

This study presents a comprehensive strategy for mitigating drying shrinkage of alkali-activated slag mortar (AASM) with the high-dosage incorporation of waste concrete powder (WCP). Response surface methodology (RSM) coupled with microstructural analysis is used to investigate the synergistic effects of WCP particle size (R), activator modulus (AM), activator content (AC), and water to solid ratio (W/S) on shrinkage behavior and matrix development. The optimized mix—WCP-R = 33.6 µm, AM = 1.23, AC = 6.03%. and W/S = 0.49—exhibits a 120-day drying shrinkage of only 1450.1 µε, significantly lower than that of conventional AASM. Microstructural observations reveal that coarser WCP particles act predominantly as fillers, enhancing stability, whereas finer particles promote gel formation but increase shrinkage. A high AM (1.6) refines the pore structure by reducing large pores (>0.05 µm), while a low W/S (0.46) decreases total porosity to 7.67%, collectively restricting moisture transport. The coexistence of C-(A)-S-H gel and hydrotalcite improves matrix integrity. Notably, this optimized HWAASM achieves a substantially reduced carbon footprint of 180 kg CO₂-eq/t, underscoring its significant environmental advantage. The findings advance the understanding of shrinkage mechanisms in high-WCP-AASM and offer an eco-friendly route for valorizing construction waste and developing low-carbon building materials. Full article