Search Results (78)

This study investigates the combined use of fly ash (FA) and plastic waste (PW) as partial replacements for cement and coarse aggregates in the production of paver blocks. Experimental mixes were developed with a substitution level of FA (10% to 30%) and PW (3% to 15%). The performance of the modified concrete block was evaluated in terms of compressive strength (CS), flexural strength (FS), ultrasonic pulse velocity (UPV), water absorption (WA), Cantabro abrasion resistance (CAR), and rapid chloride permeability test (RCPT). Experimental results revealed that the optimal mixture, containing 25% FA and 12% PW (M4), exhibited superior performance. Compared with the control mix, the 56-day compressive and flexural strengths increased by 14.1% and 15.3%, respectively. The UPV value increased to 5.1 km/s, indicating improved concrete quality and matrix densification. Durability performance was significantly enhanced, with water absorption reduced by 25.4%, Cantabro abrasion mass loss decreased by 23.7%, and chloride ion penetrability reduced by 50.0% at 56 days. Statistical analysis using two-way ANOVA confirmed that FA and PW contents significantly influenced paver block performance (p < 0.05). The economic assessment further demonstrated cost savings of up to 3.0% compared with conventional concrete paver blocks. The study demonstrates that FA and PW can be effectively valorized in paver block production, offering both economic and environmental benefits. This green approach supports sustainable construction practices and promotes efficient waste management. Full article

Waste plastic aggregate (WPA) is a promising recycled material for asphalt mixtures, but its polymeric surface can weaken binder adhesion and increase moisture-related damage, even in SBS-modified systems. Therefore, a clear need exists to identify anti-stripping agents that are compatible with WPA, rather than simply increasing WPA content in asphalt mixtures. This study evaluates the interfacial and mixture-scale performance of SBS-modified asphalt mixtures containing two WPA types, namely coarse WPA and fine WPA, treated with three liquid anti-stripping agents: amine-based agent (AS-Am), organosilane coupling-type adhesion promoter (AS-OS), and ester/surfactant-based wetting agent (AS-Es). The novelty of this study lies in selecting the anti-stripping system based on WPA–binder adhesion compatibility and validating it through moisture, rutting, rheological, and fracture performance. Binder bond strength, tensile bond strength, shear bond strength, indirect tensile strength/tensile strength ratio (ITS/TSR), Hamburg wheel tracking (HWT), multiple stress creep recovery (MSCR), and semi-circular bending (SCB) tests were conducted. AS-OS showed the best overall performance. It increased binder bond strength (BBS) by 52.8% for coarse WPA and 61.5% for fine WPA, while the optimum 0.5% dosage improved tensile bond strength by 81.0% and 97.2%, respectively. AS-OS also increased shear strength by 58.8–68.3% and improved TSR to 89.0% and 86.2%. In HWT, C-OS and F-OS reduced final rut depth by 44.0% and 45.8%, respectively. SCB results further showed higher fracture work, especially for F-OS. The findings indicate that proper anti-stripping chemistry is essential for durable WPA–SBS asphalt mixtures. Full article

Against the background of the global “dual carbon” strategic goal, low-carbon upgrading of road engineering and efficient recycling of waste plastics have become critical approaches to relieve the shortage of natural aggregates and control plastic pollution. Most existing studies only focus on the optimization of single mechanical indicators, while lacking collaborative analysis of mechanical performances and carbon reduction benefits, meaning they cannot provide sufficient scientific support for the design of low-carbon and sustainable road materials. In this study, recycled plastic aggregate (PA) was used to partially replace natural coarse aggregate, and its influence on the mechanical characteristics of cement-stabilized macadam (CSM) was systematically investigated. Combined with life cycle assessment (LCA), the carbon emission reduction potential was quantitatively evaluated, aiming to improve the toughness of road base materials and promote low-carbon sustainable development. The results demonstrate that when the PA content increases from 0% to 20%, the mechanical strength of CSM gradually decreases, while the toughness presents a steady upward trend, and the maximum carbon emission reduction rate reaches 50.8%. The optimal toughness improvement of 28.39% is obtained at the PA content of 16%. This study clarifies the internal correlation between mechanical behaviors and low-carbon benefits of recycled plastic aggregate, provides reliable technical support for the high-value utilization of waste plastics and the optimization of sustainable road materials, and offers important references for the green and low-carbon transformation of transportation infrastructure. Full article

The increasing amount of recycled plastic waste and the extensive use of construction materials both contribute significantly to CO₂ emissions, a major global concern. This study investigates the use of recycled plastic waste (PW) as a partial replacement for natural 4/10 mm coarse aggregates in concrete mix design, aiming to promote sustainable construction practices. Concrete mixes were prepared with varying levels of plastic replacement—0%, 15%, 30%, 45%, and 60% by volume—and evaluated for workability, compressive strength, tensile strength, water absorption, and microstructural properties. Results indicated that replacing aggregates with PW increased slump values, suggesting improved workability, particularly at 30–45% replacement. However, both compressive and tensile strengths exhibited a declining trend as the replacement level increased. The standard strength was maintained only at 15% replacement, achieving 35.3 MPa at 56 days compared to 37.3 MPa for the control mix. Durability tests showed reduced water absorption at low replacement levels but significant porosity and microcracking at higher percentages. Scanning Electron Microscopy (SEM) revealed weak interfacial transition zones (ITZs) between plastic waste and cement paste, with bonding weakening and micro voids increasing as replacement levels rose. A simplified life cycle assessment (LCA) suggests that while CO₂ emissions remain largely unchanged due to cement dominance, incorporating recycled plastic waste provides sustainability benefits through resource conservation and waste diversion rather than direct carbon reduction. These findings highlight that limited aggregate replacement with plastic waste can be practical, cost-efficient, and environmentally advantageous. This research underscores the potential of recycled plastics in sustainable construction, contributing to waste management and reducing reliance on natural aggregates. Full article

To address the dual challenges of improving precast cable trench joint performance and promoting solid waste recycling for carbon neutrality, this study developed a jute fiber-reinforced recycled aggregate concrete (JFRAC) and established a complete technical chain via experiments and numerical simulations. Compressive strength tests were conducted on JFRAC with varying jute fiber volume content and recycled coarse aggregate (RCA) replacement ratio to obtain their influence on the stress–strain relationship. A modified Concrete Damaged Plasticity (CDP) model was proposed by introducing correction coefficients for compressive strength and elastic modulus, achieving over 95% agreement with experimental data. Finite element simulations of cable trench joints showed that JFRAC outperforms C30 concrete, with the same compressive strength, in ultimate bearing capacity (↑4.17%), peak displacement (↑18.78%), and ductility (↑14.66%). JFRAC provides substantial environmental and economic advantages by reducing carbon emissions by 2.29% and saving costs of CNY 62.43 per meter of precast cable trench. Parametric studies indicated bolt grade and number are the primary performance influencers. Bolt grade’s impact diminishes as it increases from 8.8 to 10.9, while bolt number linearly enhances load-bearing capacity. This study provides a feasible path for JFRAC to replace conventional concrete in cable trenches, realizing both economic and environmental benefits. Full article

To promote the resource utilization of high-titanium blast furnace slag (HTBFS) and advance the development of lightweight prefabricated structures, this study developed a lightweight HTBFS concrete composite beam (HTC composite beam) by replacing natural gravel and sand in concrete with HTBFS coarse and fine aggregates, and incorporating fly ash ceramsite to reduce self-weight. Symmetrically two-point bending tests were conducted on five HTC composite beams with different reinforcement ratios and precast heights, one Integrally cast HTC beam, and one ordinary concrete composite beam. The failure modes, load-carrying capacities, and deformation characteristics were evaluated. The loading process was also simulated using Abaqus, and the numerical results were compared with experimental data for validation. The results indicate that HTC composite beams satisfy the plane-section assumption; increasing the reinforcement ratio improves the load-carrying capacity, and the precast height has positive effect of HTC composite beams’ load-carrying. Compared with the ordinary concrete composite beam, the HTC composite beam exhibited a 12.30% higher load-carrying capacity, smaller deflection, and better deformation capacity. Multiple energy-based indices demonstrated that HTC composite beams possess favorable post-cracking plastic deformation capacity and stiffness retention. The difference between the finite element simulations and experimental results was less than 5%, confirming both the reliability of the numerical model and the accuracy of the experimental data. An economic analysis revealed that this structural system has significant potential for carbon reduction and cost savings, with an overall saving of approximately 141,000–500,000 CNY. These findings provide theoretical and engineering support for the application of HTC composite beams in prefabricated construction and have positive implications for reducing project costs and promoting the industrialization and low-carbon development of prefabricated buildings. Full article

The increasing global production of plastic (P) waste presents a critical environmental challenge, while the construction industry’s demand for sustainable materials continues to grow. The building industry’s reliance on natural aggregates, a contributor to environmental degradation, requires sustainable alternatives. Utilizing plastic waste as a partial aggregate substitute in concrete offers dual advantages: preserving limited resources and redirecting waste from landfills. This research uses advanced machine learning (ML) to forecast the mechanical properties of P waste concrete. Random Forest (RF) and eXtreme Gradient Boosting (XGBoost) models with particle swarm optimization (PSO) were developed to predict compressive and tensile strengths of P waste concrete. A comprehensive dataset comprising 196 datapoints for compressive strength (CS) and 100 datapoints for tensile strength (TS) of P waste concrete was collected from the literature. The input parameters encompassed the plastic (P), cement (C), water-to-cement ratio (W/C), coarse aggregate (CA), fine aggregate (FA), and curing age (Age), while the outputs were CS and TS of P waste concrete. The constructed models were assessed utilizing various statistical metrics. The findings indicate that coefficient of determination of both XGBoost (CS, R² = 0.9911, and TS, R² = 0.9947) and RF (CS, R² = 0.9757, and TS, R² = 0.9737) models performed well, with XGBoost indicating better performance with fewer prediction errors. SHAP analysis emphasizes the substantial effect of P waste on concrete strength properties followed by C and Age. Furthermore, GUIs for predicting TS and CS of concrete containing P waste utilizing both RF and XGBoost models were developed. Overall, this study not only achieves superior accuracy through hybrid PSO-ML models but also contributes to sustainable construction materials and computational material science, offering a data-driven framework for optimizing mix designs that incorporate plastic waste, which can accelerate its adoption in eco-friendly engineering applications. Full article

This study examines the effectiveness of pervious concrete pavements as a sustainable and cost-effective stormwater management technique, particularly by incorporating locally sourced recycled materials into their design. It evaluates the stormwater treatment potential of three pervious concrete pavement types incorporating recycled plastic, glass, and crushed concrete aggregates, with six design variations produced using 25% and 50% replacements of coarse aggregates from these materials. The key properties of pervious concrete, namely compressive strength, porosity, unit weight, and infiltration, and key water quality indicators, namely pH, electrical conductivity (EC), total suspended solids (TSS), colour, turbidity, chemical oxygen demand (COD), nitrate (NO₃⁻), and orthophosphate (PO₄³⁻), were analysed. Results indicated an overall improvement in the quality of the stormwater runoff passed through all pervious concrete pavements irrespective of composition. Notable reductions in turbidity, TSS, colour, COD, PO₄³⁻, and NO₃⁻ underscored the effectiveness of pervious concrete containing waste materials in the treatment of stormwater runoff. Pervious concrete pavements with 25% recycled concrete exhibited optimal performance in reducing TSS, COD, and PO₄³⁻ levels, while the 50% recycled concrete variant excelled in diminishing turbidity. However, the study found that the use of recycled materials in pervious concrete pavements affects properties like compressive strength and infiltration rate differently. While incorporating 25% and 50% recycled concrete aggregates did not significantly reduce compressive strength, the effectiveness of stormwater treatment varied based on the mix design and type of recycled material used. Thus, this study highlights the potential of utilizing recycled waste materials in pervious concrete pavements for sustainable stormwater management. Full article

Numerical simulations, unlike experimental studies, eliminate material and setup costs while significantly reducing testing time. In this study, a random distribution program for steel-recycled polyethylene terephthalate hybrid fiber recycled concrete (SRPRAC) was developed in Python (3.11), enabling direct generation in Abaqus. Mesoscopic simulation parameters were calibrated through debugging and sensitivity analysis. The simulations examined the compressive failure mode of SRPRAC and the influence of different factors. Results indicate that larger recycled coarse aggregate particle sizes intensify tensile and compressive damage in the interfacial transition zone between the coarse aggregate and mortar. Loading rate strongly affects outcomes, while smaller mesh sizes yield more stable results. Stronger boundary constraints at the top and bottom surfaces lead to higher peak stress, peak strain, and residual stress. Failure was mainly distributed within the specimen, forming a distinct X-shaped damage zone. Increasing fiber content reduced the equivalent plastic strain area above the compressive failure threshold, though the effect diminished beyond 1% total fiber volume. During initial loading, steel fibers carried higher tensile stresses, whereas recycled polyethylene terephthalate fibers (rPETF) contributed less. After peak load, tensile stress in rPETF increased significantly, complementing the gradual stress increase in steel fibers. The mesoscopic model effectively captured the stress–strain damage behavior of SRPRAC under compression. Full article

Recycled coarse aggregates (RCA) offer an alternative to natural coarse aggregates in concrete production, reducing natural aggregate extraction and landfill burdens and potentially lowering embodied energy and CO₂ emissions. This study leverages machine learning algorithms to predict the dynamic yield stress (DYS) and plastic viscosity (PV) of RCA concrete (RCAC). A database of 380 RCAC mixtures, incorporating 11 input features, was analyzed using six machine learning models: Artificial Neural Network (ANN), Decision Tree (DT), Random Forest (RF), Extreme Gradient Boosting (XGBoost), Light Gradient Boosting Machine (LightGBM), and Support Vector Machine (SVM). The model performance was compared, followed by sensitivity analyses to identify critical factors influencing DYS and PV. For DYS, the DT model demonstrated the highest predictive performance (testing R²/RMSE/MAE = 0.95/18.25/13.99; others: 0.90–0.93/12.14–26.10/15.40–19.50) due to its robustness on smaller datasets. The XGBoost model led for PV (testing R²/RMSE/MAE = 0.93/7.06/4.58; others: 0.82–0.89/8.69–11.20/6.06–7.51) owing to its sequential residual minimization that captures nonlinear interactions. Sensitivity analyses revealed that polycarboxylate superplasticizer content and water-to-binder ratio significantly influence DYS, while cement content and saturated-surface-dried water absorption of RCA (i.e., measured with open pores filled and the aggregate surface dry) dominate PV. The time-dependent role in affecting PV was also highlighted. By optimizing and comparing different machine learning algorithms, this study advances predictive methodologies for the rheological properties of RCAC, addressing the underexplored use of machine learning for RCAC rheology (DYS and PV) and the limitations of traditional empirical rheology methods, thereby promoting the efficient use of recycled materials in sustainable concrete design. Full article

Due to the shortage of construction aggregates, carbonate rock aggregates—including mainly limestone aggregates—have long been used in structural concrete in many countries worldwide. On the other hand, earlier tests on the shear fracture toughness of concretes with limestone aggregates were very limited and were even abandoned for many years. For the above reasons, in this paper, completely new fracture toughness tests were performed according to the mode II fracture for limestone concretes with different grain size distributions. Two types of aggregate grain were used, i.e., two with maximum grain sizes of 8 mm (M1 series concrete) and 16 mm (M2 series concrete). During the experiments, the critical stress-intensity factor (K_IIc) and critical unit work of failure (J_IIc) were determined. Based on the conducted studies, it was found that higher values of fracture mechanics parameters were noted as the grain sizes of the aggregate used increased. The increases in the analyzed fracture mechanics parameters were noticeably greater in the M2 series concrete compared to the results for the M1 series concrete, specifically by 27% for K_IIc and 35% for J_IIc. In addition to macroscopic tests, detailed microstructural analyses of the ITZ area between the coarse aggregate grains and the cement matrix were conducted. Based on the captured images, it was determined that, in the M1 series concrete, the contacts between the aggregate grains and the cement paste exhibit a loose structure with visible microcracks. In contrast, the M2 series concrete showed no visible damages within the ITZ area itself nor at their displacement at a distance of approximately a few μm away from this area. This microstructure of both materials resulted in the M1 series concrete being more prone to rapid and sudden fracture propagation, leading to its brittle behavior during the fracture process. In contrast, the large, well-developed limestone aggregate grains in the M2 series concrete facilitated improved stress transfer beyond the ITZ area into the cement matrix, preserving the continuity of the material structure and consequently leading to quasi-plastic behavior of the concrete during the fracture process. The novelty and utilitarianism of the research undertaken result from the fact that exploring the properties of concretes with limestone aggregates using mode II fracture is an important aspect of evaluating the durability and safety of concrete structures subjected mainly to shear forces. Full article

The growing disposal of used tyres and plastic waste in landfills poses a significant environmental challenge. This study investigates the potential of utilizing used tyre rubber and macro-synthetic fibres (MSFs) made from recycled plastics in fibre-reinforced rubberized concrete (RuFRC). Various percentages of tyre rubber shreds were used to replace coarse aggregates, calculated as 10%, 20%, and 30% of the volume of fine aggregates; fibre dosages (0%, 0.25%, 0.5%, 0.75%, and 1% by volume) were incorporated into the mix, and a series of physical, mechanical, and durability properties were evaluated. The results show that, as the fibre and rubber content increased, the slump of RuFRC decreased, with the lowest value obtained for concrete with 1% fibre and 30% rubber. The density of RuFRC decreases as the rubber percentage increases due to air voids and increased porosity caused by the rubber. The strength properties of RuFRC were found to decline with the increase in the rubber content, with mixes containing 30% rubber exhibiting reductions of about 60% in compressive strength, 27% in tensile strength, and 13% in flexural strength compared to the control specimen. Durability testing revealed that an increased rubber content led to higher water absorption, water penetration, and chloride ion permeability, with 30% rubber showing the highest values. However, lower rubber content (10%) and higher fibre dosages improved the durability characteristics, with water absorption reduced by up to 5% and shrinkage strains lowered by about 7%, indicating better compaction and bonding. These results indicate that RuFRC with moderate rubber and higher fibre content offers a promising balance between sustainability and performance. Full article

The increasing demand for sustainable construction materials has driven research into low-carbon geopolymers that mitigate both cement-related emissions and plastic and glass waste accumulation. This study explores the development of geopolymer concrete incorporating fly ash (FA), slag (S), and FA + S blends, with 10% recycled crushed glass (RCG) and recycled plastic waste (RPW) as partial coarse aggregate replacements. Compressive strength testing revealed that FA + S-based geopolymers (25FA + S) with 100% ordinary Portland cement (OPC) replacement achieved a 7-day strength of 24.6 MPa, representing a 98% improvement over control specimens. Slag-based geopolymers demonstrated water absorption properties comparable to OPC, indicating enhanced durability. Microstructural analyses using SEM, XRD, and EDS confirmed the formation of a dense aluminosilicate matrix, with slag promoting FA reactivity and reinforcing interfacial transition zone (ITZ). These effects contributed to superior mechanical performance and water resistance. Despite minor shrinkage-induced cracking, full OPC replacement with S or FA + S geopolymers outperformed control specimens, consistently exceeding the target strength of 15 MPa required for low-impact, single-story housing applications within seven days. These findings underscore the potential of geopolymer systems for rapid and sustainable construction, offering an effective solution for reducing carbon footprints and repurposing industrial waste. Full article

This study underscores the importance of sustainable practices by exploring the utilization of recycled plastic within the global construction industry. Plastic recycling has emerged as a crucial strategy that aligns with environmental, social, and economic sustainability indicators. Currently, substantial volumes of plastic waste are either deposited in landfills or incinerated, neglecting the potential to harness its embodied energy and the energy consumed for producing virgin materials. A key advantage of plastic lies in its promising mechanical properties. Concrete mix design is fundamental to a wide range of construction applications, including brick walls, reinforced concrete slabs, and concrete pavements. Despite the adoption of recycled plastic in construction materials in various countries, its widespread implementation remains limited. This is primarily due to the scarcity of experimental research in this area and the absence of a robust waste management system. This research specifically investigates the reuse of two common types of plastic waste: polyethylene terephthalate (PET) and high-density polyethylene (HDPE) to mitigate plastic waste accumulation in landfills and enhance the performance of construction materials. The study investigates the use of recycled HDPE and PET as a replacement for coarse aggregates in concrete pavement mixtures. While recycled PET is more prevalent in concrete applications, recycled HDPE has demonstrated exceptional efficiency and durability. The recycling method used in this research is the mechanical recycling method due to its superior effectiveness in comparison with other methodologies. This research assesses the performance of recycled PET and HDPE in concrete pavement, aiming to diminish non-renewable energy consumption by 15–20%, curtail the carbon footprint by 15–30%, and decrease plastic waste in landfills by 20–30% compared to conventional concrete. Full article

This study investigates the use of demolition waste as recycled coarse aggregates (RCAs) to replace natural coarse aggregates (NCAs), and the use of ground granulated blast slag (GGBS) and limestone filler (LF) as a supplementary cementitious material, in self-compacting concrete (SCC), with proportions of 150 kg/m³ for GGBS and 180 kg/m³ for LF. Various SCC mixtures were prepared with RCA proportions of 0, 25, 50, 75, and 100%, while maintaining fixed dosages of LF and GGBS. Initially, RCA was incorporated in a dry state, followed by a water dosage adjustment for mixtures containing 100% RCA, equivalent to 20 min of RCA absorption. The experimental investigation evaluated the evolution of flow properties through tests such as slump flow, flow time (T500), L-box, sieve stability, fresh density, and air content. The static yield stress and plastic viscosity were also calculated using mathematical models. Additionally, hardened properties, including short-term and long-term compressive strength and capillary water absorption, were assessed. An environmental impact analysis of using demolition waste was conducted, revealing that a total NCA replacement with RCA is viable for both fresh and hardened states, provided that the RCA water absorption is managed and a reactive mineral additive is incorporated. For a 50% replacement of natural aggregates with recycled aggregates, this approach significantly reduces environmental impacts, lowering fossil fuel consumption by up to 35% and greenhouse gas emissions by up to 32%. Full article