Construction and Demolition Wastes (CDW) serves as an effective filler for highway subgrades, demonstrating commendable performance characteristics. The efficient utilization of CDW not only contributes to environmental sustainability but also yields significant economic benefits. This study employs discrete element simulation to develop a triaxial sample model comprising particles with four distinct levels of sphericity. By varying the combinations of sphericity, brickconcrete ratio, and void ratio, triaxial simulation tests are conducted, and the critical state soil mechanics framework is applied to fit the critical state line (CSL) of the samples. The results indicate that sphericity, brick-concrete ratio, and void ratio substantially influence the macroscopic mechanical properties of CDW. Notably, as sphericity increases, the peak deviatoric stress of the samples decreases, and significant volume deformation occurs. The slope of the CSL in the q-p ' plane diminishes, while the slopes of both forms of the CSL in the e-log p ' plane increase. Furthermore, a decrease in the brick-concrete ratio enhances the anti-deformation and compressive capacities of the samples. As the brick-concrete ratio decreases, both the slopes and intercepts of the CSL in the e-log p ' plane exhibit an upward trend. Conversely, an increase in the void ratio leads to a reduction in the overall strength and anti-deformation capacity of the specimens, an increase in the compressibility of the specimen volume, an elevation of the CSL slope on the q-p ' plane, and a gradual increase in both the slope and intercept of the semilogarithmic form of the CSL on the e-log p ' plane, as well as a gradual increase in the slope of the power-law form of the CSL.

Sustainability is defined as the process of developing and responsibly sustaining a healthy built environment based on resource-efficient and ecological principles. When it comes to sustainability, earthen construction is a good choice because of its minimal carbon impact and lower operating expenses. This study investigates the cost comparison between Alker and a reinforced concrete office with a dimension of 6 x 6 m. Alker is a stabilised form of earthen building. Based on the dry weight of the soil, it contains 10% gypsum, 2% lime, and 20%-22% water. Shredded plastic waste (SPW) was added to Alker to improve its properties with the addition of the environmental effect of plastic waste. The results showed that the office built with reinforced concrete had a total cost of Turkish Lira;119 348.57 (6630), whereas the building built with Alker materials had a total cost of Turkish Lira;103 474.19 (5748). Therefore, offices built with Alker's added SPW are 13% cheaper than offices built with reinforced concrete. Alker modified with shredded plastic waste has been demonstrated to be a sustainable building material with enhanced properties.

Recycling paper sludge waste (PSW) into inexpensive sheets for applications in household interiors, construction, and footwear is a sustainable approach to resource utilisation and pollution reduction. A flexible recycled sheet (FRS) in board form was developed using cellulosic-based PSW from the paper industry and a styrene-butadiene rubber (SBR) binder. Various SBR concentrations were tested to determine the optimal amount for superior mechanical properties. The produced FRS was characterised using Fourier transform infrared spectroscopy, thermogravimetric analysis, high-resolution scanning electron microscopy, and energy-dispersive X-ray spectroscopy. FRS made with 1000 g of PSW:300 ml of SBR exhibited enhanced mechanical properties, including tensile strength (62.32 +/- 0.51 MPa), elongation at break (51.99 +/- 0.94%), tearing strength (17.76 +/- 0.45 N/mm), and flexibility (6.98 +/- 0.24%). A biodegradation study, conducted per ASTM D 5988-03, assessed environmental impact by measuring carbon-to-CO2 conversion in soil over 90 days. All FRS samples showed similar degradation within the first 30 days, with FRS 5 degrading significantly faster thereafter due to its higher cellulose and hemicellulose content. This highlights the potential of PSW-based FRS as an environmentally friendly and mechanically robust material for diverse applications.

Calcium carbide slag (CCS), phosphogypsum (PG), and red mud (RM), three types of industrial solid wastes, were employed to improve tunnel muck for assessing the feasibility of their reuse. A series of indoor tests were conducted to investigate the effects of their contents on the physical and mechanical properties of the improved tunnel muck. Microscopic tests were also conducted to reveal the improvement and interaction mechanisms involved. Results indicate that the incorporation of CCS, PG, and RM can significantly improve and enhance the physical and mechanical properties of tunnel muck. The improved tunnel muck containing 2% PG and 6% RM shows higher early strengths as CCS content exceeds 4%. However, after curing for more than 14 days, the unconfined compressive strength (UCS) of the tunnel muck with 4% PG and 4% RM is the maximum regardless of the CCS content. Microscopic analysis shows that reactive substances in industrial solid waste react chemically with soil components, exchanging ions and forming cementitious products such as calcium hydroxide, calcium silicate hydrate (C-S-H), calcium aluminosilicate hydrate (C-A-S-H), and ettringite (AFt). They bind, fill, and encapsulate soil particles, compacting the soil and significantly enhancing the physical and mechanical properties of tunnel muck. Moreover, there is a notable mutual synergy between PG and RM, primarily attributed to their acid-base neutralization and the complementary action of reactive ions. The improved tunnel muck containing 4% CCS, 4% PG, and 4% RM demonstrates the highest enhancement efficiency.

Hazardous alkylphenol wastes (HAPW) are a class of organic semisolid waste characterized by large production, complex composition and difficulties associated with recycling. Their generation and disposal lead to significantly environmental issues, including water and soil pollution, and present a substantial industrial challenge. To address these issues, a sustainable, low-carbon strategy for the high-value utilization of HAPW has been proposed. We take HAPW as a compatibilizer in the production of epoxy asphalt for road construction materials. Experimental results show that the HAPW-based epoxy asphalt containing 19.5 wt% HAPW exhibited optimal mechanical properties (tensile strength: 4.16 MPa; elongation at break: 164.92 %), exceeding industrial standards and outperforming epoxy asphalt produced using commercial cardanol through conventional processes. With a detailed molecular dynamics simulation, it is found that the HAPW plays two key roles in enhancing the interactions between epoxy resins and asphalt: (i) HAPW generates numerous hydrogen bonds with both asphalt and epoxy resin phases, strengthening noncovalent interactions and improving interfacial miscibility between the two phases. (ii) HAPW could react with the epoxy resin through the phenolic hydroxyl group, which further improves the interactions between epoxy resin and asphalt. This approach facilitates the treatment of hazardous organic waste in an environmentally sustainable and low-carbon way, enabling the recovery and repurposing of organic waste into high-valued products. Consequently, it promotes the resource utilization of industrial wastes while simultaneously contributing to a reduction in carbon emissions.

Geosynthetics have increasingly been used in geotechnical engineering applications due to their numerous benefits, including the cost-effectiveness, reliability and contribution to sustainability. When employed in transport infrastructure projects, geosynthetics may perform a variety of functions, leading to increased stability and longevity of the system. This paper describes a laboratory study carried out using a large-scale direct shear test apparatus to characterise the direct shear behaviour of the interfaces between a recycled construction and demolition (C&D) material and two geosynthetics (a geogrid and a geocomposite) subjected to cyclic normal loading. The direct shear tests were performed under a constant shear displacement rate, while the normal loading varied cyclically at predefined frequency and amplitude values. Direct shear tests under static normal loading were also performed for comparison purposes. Test results have shown that the interface shear strength and dilation behaviour tend to decrease under cyclic normal loading and are influenced by the applied frequency and amplitude. The peak and large displacement shear strengths of the interface with the geogrid exceeded those reached when the geocomposite was used, which may be attributed to more effective interlocking of the aggregates within the geogrid apertures.

There has been a growing concern on the health effect of edible plants growing near/on/within the vicinity of dumpsites. This study investigated two edible vegetables: Amarathus hybridus and Talinum triangulare (Jacq) grown in the vicinity of a major informal dumpsite of electronic waste in Nigeria. The levels of polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and heavy metal concentrations in the vegetables were measured. The health risks of consuming the vegetables were assessed using the hazard index (HI), lifetime cancer risk (LCR), estimated daily intake (EDI), and hazard quotient (HQ). Using the Ames Salmonella fluctuation test on Salmonella typhimurium (TA100 and TA98) and the SOS chromo test on Escherichia coli (PQ37), the mutagenicity and genotoxicity of the vegetables were evaluated. The two vegetables have elevated levels of heavy metals, PBDEs, PCBs, and hazardous PAHs. Compared to A. hybridus, , T. triangulare was more contaminated. The amounts of organic constituents and heavy metals in the vegetables correlated favorably. The levels of the HQ, HI, and LCR were above the suggested guideline values, indicating a significant risk of both carcinogenic and non-carcinogenic consequences, particularly in children. The two vegetables were mutagenic even at 50 % concentration in the Ames test. This was corroborated with SOS-chromo test results showing that the two vegetables were indeed genotoxic. This study demonstrated the harmful effects of growing food crops close to dumpsites; therefore, sufficient measures should be implemented to stop farmers and individuals from utilizing dirt from dumps as fertilizer or from planting in soil that has been used as a dump in the past or present.

This paper utilizes industrial wastes, including slag powder, desulfurized gypsum, fly ash, and construction waste, to solidify municipal sludge and develop a new type of landfill cover material. To investigate the durability of solidified sludge under wet-dry cycles, this study systematically analyzes its mechanical properties-such as volume shrinkage rate, unconfined compressive strength, and permeability coefficient-along with microstructural characteristics like pore structure, micro-morphology, and hydration products. In addition, the impermeability of the solidified sludge cover under varying rainfall conditions was assessed using rainfall simulation tests. After 20 wet-dry cycles, the solidified sludge samples exhibited volume shrinkage between 0.56% and 0.85%, unconfined compressive strength from 1.31 to 4.55 MPa, and permeability coefficients ranging from 9.51 x 10- 8 to 5.68 x 10- 7 cm/s. Portions of the gelatinous hydration products in the solidified sludge experienced discrete damage, leading to an increase in microporous volume. However, the overall structural integrity of the solidified sludge was maintained. The 3-layer landfill cover system was constructed using engineering soil, coarse construction waste aggregate, and solidified sludge and resisted strong precipitation. The 40 cm thick solidified sludge acted as an impermeable layer and yielded a good water-blocking effect. This study provides data support the application and technical advancement of solidified sludge as a landfill cover material.

This paper aimed to investigate the feasibility of partially or completely replacing natural aggregates with recycled aggregates from construction and demolition wastes for low-carbon-emission use as coarse-grained embankment fill materials. The laboratory specimens were prepared by blending natural and recycled aggregates at varying proportions, and a series of laboratory repeated load triaxial compression tests were carried out to study the effects of material index properties and dynamic stress states on the resilient modulus and permanent strain characteristics. Based on the experimental results and by considering the main influencing parameters of the resilient modulus and permanent deformation, an artificial neural network (ANN) prediction model with optimal architecture was developed and optimized by the particle swarm optimization (PSO) algorithm, and its performance and accuracy were verified by supplementary analyses. A shakedown state classification method was proposed based on the unsupervised clustering algorithm, and a prediction model of critical dynamic stress was established based on the machine learning (ML) method and the shakedown state classification results. The research results indicate that the stress state has a greater influence on the resilient modulus and permanent deformation characteristics than other factors, and the shear stress ratio has a significant effect on the shakedown state. The resilient modulus and critical dynamic stress of such specimens vary linearly with confining pressure. The improved PSO-ANN prediction model exhibits high prediction accuracy and robustness, superior to several other commonly used ML regression prediction algorithms. The resilient modulus and critical dynamic stress prediction methods based on ML algorithms can provide technical guidance and theoretical basis for the design and in-service maintenance of similar unbound granular materials.

The utilization of industrial wastes as feedstock for binders in soil stabilization is a promising approach toward environmental consequences; however, the optimization of chemical compositions and gradation are commonly disregarded especially for binders derived from multiple industrial wastes. This study presents a novel framework for designing multiple industrial waste blends (MIWB) consisting of ground blast furnace slag (GB), fly ash (FA), silica fume (SF), and calcium carbide residue (CR) and assesses its feasibility and performance in soil stabilization. The concept of three chemical moduli (TCM) and the strength activity index (SAI) are applied to control chemical composition, and Dinger-Funk particle size distribution is adopted to attain optimal gradation. A case study exemplifies sediment stabilization utilizing MIWB designed, and sodium hydroxide (NH), sodium metasilicate nonahydrate (NS), sodium sulfate (SS), and aluminum sulfate (AS) are used as chemical additives, the mechanical and microstructural studies by Atterberg limits, compaction, unconfined compressive strength, onedimensional consolidation, cyclic wetting-drying, X-ray diffraction, scanning electron microscopy and nuclear magnetic resonance tests are comprehensively examined. The outcomes demonstrate that: (i) MIWB is more efficient than ordinary Portland cement (OPC) in enhancing the compressibility and durability of stabilized sediment, and the optimal mix design of the composite binder was 14.25, 47.5, 9.5, 23.75, and 5 wt% of GB, FA, SF, CR, and AS respectively. (ii) The sulfate additives can dramatically improve the strength development of designed MIWB stabilized sediment than that of alkaline additives, (iii) The C-S-H, C-A-S-H, and AFt crystals are identified as the primary reaction products, arising from pozzolanic reactions between active phases present in the industrial waste. (iv)The pore volume of stabilized samples is reduced due to the excellent filling and cementation effects, contributing to higher mechanical properties. In particular, MIWB has been applied and proven effective in engineering practice.