Search Results (586)

The main objective of this study was to evaluate the long-term mechanical performance and shrinkage behavior of ultrahigh-performance concrete (UHPC) in which the granulated ground blast-furnace slag (GGBFS), used as part of the binder, is replaced partially or fully with ferronickel slag (FNS). The aim was to identify potential strength reduction and expansion problems associated with the use of FNS powder. For steam-cured UHPC, the compressive strength of the FNS100 (124.8 MPa) was comparable to that of the control case (FNS0, 125.1 MPa), and the tensile strength showed only a 0.3 MPa difference. Under constant-temperature and constant-humidity conditions, all mixtures satisfied the design strength standard of 120 MPa by the end of the curing period. Considering constant-temperature and constant-humidity conditions, shrinkage evaluation revealed that the FNS100_NON_AD (no shrinkage-reducing and expansive agents) exhibited 3.8 times greater shrinkage compared to FNS0, while other mixtures remained within a narrow range. These results indicate that shrinkage was governed more by the presence and type of admixtures than by the FNS replacement rate itself. This study demonstrated that FNS has sufficient potential for use as a binder in UHPC and encourages further research to optimize admixture use for long-term durability and shrinkage control. Full article

One-part geopolymers (OPG) offer a low-carbon alternative to Portland cement, yet mix design remains largely empirical. This study couples machine learning with SHAP (Shapley Additive Explanations) to quantify how mix and curing factors govern performance in Ca-containing OPG. We trained six regressors—Random Forest, ExtraTrees, SVR, Ridge, KNN, and XGBoost—on a compiled dataset and selected XGBoost as the primary model based on prediction accuracy. Models were built separately for four targets: compressive strength at 3, 7, 14, and 28 days. SHAP analysis reveals four dominant variables across targets—Slag, Na₂O, Ms, and the water-to-binder ratio (w/b)—while the sand-to-binder ratio (s/b), temperature, and humidity are secondary within the tested ranges. Strength evolution follows a reaction–densification logic: at 3 days, Slag dominates as Ca accelerates C–(N)–A–S–H formation; at 7–14 days, Na₂O leads as alkalinity/soluble silicate controls dissolution–gelation; by 28 days, Slag and Na₂O jointly set the strength ceiling, with w/b continuously regulating porosity. Interactions are strongest for Slag × Na₂O (Ca–alkalinity synergy). These results provide actionable guidance: prioritize Slag and Na₂O while controlling w/b for strength. The XGBoost+SHAP workflow offers transparent, data-driven decision support for OPG mix optimization and can be extended with broader datasets and formal validation to enhance generalization. Full article

Conventional ridging and mulching machines struggle to perform effectively in yellow sand substrates due to their loose texture, high collapsibility, and strong fluidity, which compromise ridge stability and operational quality. To address these challenges, this study proposes the development of an integrated rotary tillage, ridging, and film-mulching machine specifically designed to meet the agronomic requirements of tomato cultivation in greenhouse environments with yellow sand substrate. Based on theoretical analysis and parameter calculations, a soil transportation model was established, and the key structural parameters—such as blade arrangement and helical shaft geometry—were determined. A discrete element method (DEM) simulation was employed to construct a contact model for the yellow sand–slag mixed substrate. A combination of single-factor experiments and Box–Behnken response surface methodology was used to investigate the effects of forward speed, shaft rotational speed, and tillage depth on ridge stability and operational performance. The simulation results indicated that a forward speed of 0.82 m·s⁻¹, shaft speed of 260 rpm, and tillage depth of 150 mm yielded the highest ridge stability, with an average of 95.7%. Field trials demonstrated that the ridge top width, base width, height, and spacing were 598.6 mm, 802.3 mm, 202.4 mm, and 1002.8 mm, respectively, with an average ridge stability of 94.3%, differing by only 1.4 percentage points from the simulated results. However, a quantitative traction/energy comparison with conventional equipment was not collected in this study, and we report this as a limitation. The energy consumption is estimated based on power usage and effective field capacity (EFC) under similar operating conditions. Soil firmness reached 152.1 kPa, fully satisfying the agronomic requirements for tomato cultivation. The proposed machine significantly improves operational adaptability and ridge stability in yellow sand substrate conditions, providing robust equipment support for efficient greenhouse farming. Full article

Alkali-activated materials (AAMs) offer a promising low-carbon alternative to Portland cement, but their development has been dominated by fly ash and slag, whose availability is increasingly limited. This research explores waste brick powder (WBP) and metakaolin residue (RN), two abundant yet underutilized by-products, as blended precursors for sustainable binder design. The novelty lies in demonstrating how complementary chemistry between crystalline-rich WBP and amorphous RN can overcome the drawbacks of single-precursor systems while valorizing construction and industrial residues. Pastes were prepared with varying WBP/RN ratios, activated with alkaline solutions, and characterized by Vicat setting tests, isothermal calorimetry, XRD with Rietveld refinement, MIP, SEM, and mechanical testing. Carbon footprint analysis was performed to evaluate environmental performance. Results show that WBP reacts very rapidly, causing flash setting and limited long-term strength, whereas the incorporation of 30–50% RN extends setting times, sustains dissolution, and increases amorphous gel formation. These changes refine the formed reaction products, leading to compressive strengths up to 39 MPa and flexural strengths of 8 MPa at 90 days. The carbon footprint of all blends remained 392–408 kg CO₂e/m³, thus providing about a 60% improvement compared to conventional Portland cement paste. The study establishes clear design rules for waste-derived blended precursors and highlights their potential as circular, low-carbon binders. Full article

Exposure of individuals to electromagnetic fields in a wide area of daily life necessitated making spaces-structures healthier against electromagnetic fields. In this study, waste copper slag and carbon fibers were added to the cement mortar in different proportions with substitutes and additives. Physical, mechanical, electromagnetic shielding and microstructure studies were carried out on the produced composite mortars at different ages. It was determined that the mechanical strengths of composite mortars were superior to those of reference mortar samples. It was observed that electromagnetic shielding effectiveness was more positive with copper slag and especially carbon fiber additions. The highest electromagnetic shielding values were obtained in mortars containing 50% copper slag and 0.5% carbon fiber. Additionally, it was determined that copper slag, stored as an environmental waste, could be suitable for use in cementitious mortar systems. These composites offer promise for sustainable building designs in terms of both environmental performance and structural material stability. Full article

Foundry slag has different characteristics from blast furnace slag, such as its high SiO₂ content and low basicity (CaO/SiO₂ < 1), which prevent it from being used as a cementitious component. Lime slurry is a waste product with a high CaO content and can be used to increase the basicity of the mixture. The aim of this study is to obtain new supplementary, eco-cementitious material composed of foundry slag and lime sludge. The compositions were designed with binary basicity (molar ratio of CaO/SiO₂) ranging from 1.0 to 1.4. Clinker was replaced with the proposed material in the range of 6–34 wt% and the performance of the different cement compositions was tested. The results showed that replacing 20 wt% of clinker with the new eco-cementitious material with binary basicity of 1.2 resulted in cement with the same mechanical strength as the reference cement. The new material reacted with free CaO to generate additional calcium silicate hydrate. The initial setting time of the cement containing the new eco-cementitious material was 240 min, acting as hydration reaction retardant. The technical feature of the new eco-cementitious material allows the use of both wastes in cement composition, contributing to the requirements of circular economy. Full article

Balancing stress wave attenuation with structural integrity is recognized as a critical challenge for protective materials in underground defense systems. A novel high-titanium slag (HTS) concrete featuring multiscale pores is proposed to address this dilemma. Large-particle porous HTS aggregates are embedded into cement mortar, enabling mechanical robustness comparable to conventional concrete alongside significant stress wave dissipation. Wave scattering and gas–solid interfacial reflections are induced by the multiscale pore architecture, effectively attenuating energy propagation. A dense interface transition zone between HTS aggregates and the cement mortar is confirmed through microscopic characterization, ensuring structural coherence. Wave attenuation is revealed by Split Hopkinson Pressure Bar tests to primarily originate from pore-driven reflections rather than impedance mismatch. A groundbreaking strategy is offered for designing blast-resistant materials that harmonize dynamic energy dissipation with structural durability, advancing the development of resilient underground infrastructure. Full article

This study investigates how short- and long-term aging affect the microwave self-healing of steel slag asphalt mixtures (SSAMs). Binder-level healing was tested using a dynamic shear rheometer (DSR), and mixture-level crack behavior was analyzed using beam bending tests (BBTs) and digital image correlation (DIC). Aging clearly reduced self-healing, with long-term aging causing the largest decline. Among the mixtures, OGFC-13 was most sensitive, while SMA-13 was least affected. Aging increased stiffness, reduced crack resistance, and shortened crack initiation time, leading to lower healing efficiency under microwave treatment. After heating, cracks propagated faster, indicating increased brittleness. These results quantify the impact of aging on performance and highlight the limitations of microwave repair, providing guidance for maintenance strategies and mixture design to improve long-term pavement performance. Full article

Biomass combustion for the production of electricity and heat remains one of the most widespread renewable energy technologies. Biomass is commonly utilized in fluidized bed combustion systems. Over the years, numerous issues related to the preparation and combustion of biomass in fluidized beds have been identified, including fouling and slagging, which involve the formation of deposits. These phenomena can be mitigated through various methods, including design modifications to boilers, the application of additives, and the careful selection and classification of fuel. Several fuel indices have been proposed to predict the behavior of fuels in terms of their tendency to cause fouling and slagging. Most of these indices were developed for fossil fuels, and the discrepancies between them suggest that although these indices are widely applied, their applicability to agricultural residues, such as straw, remains uncertain. Researchers working in this field emphasize the need for further research, particularly focusing on the comparison of developed indices with the results of biomass combustion at both laboratory and industrial scales. In this study, ten assortments of straw sourced from Poland were selected, and chemical composition analyses were conducted to determine selected fuel indices. The analyzed straw samples were then combusted in a 100 kWₜₕ laboratory-scale circulating fluidized bed unit. Using a specialized austenitic steel probe, the growth rate of the deposit was measured. The collected deposit masses for each straw type were then compared with the calculated fuel indices. The best correlation between the interpretation of the index values and the deposit mass on the probe was observed for the Rs index. However, due to the low sulfur content of straw, Rs numerical interpretation was not adequate. Overall, the indices indicating both good correlation coefficients and an appropriate numerical interpretation for fouling tendency were B/A, Fu, and Cl. Full article

Rapid population growth and accelerating urbanization are intensifying the demand for construction materials, particularly concrete, which is predominantly produced with Portland cement and natural aggregates. This reliance imposes substantial environmental burdens through resource depletion and greenhouse gas emissions. Within the framework of sustainable construction, recycled aggregates and industrial by-products such as fly ash, slags, crushed glass, and other secondary raw materials have emerged as viable substitutes in concrete production. At the same time, three-dimensional concrete printing (3DCP) offers opportunities to optimize material use and minimize waste, yet it requires tailored mix designs with controlled rheological and mechanical performance. This review synthesizes current knowledge on the use of recycled construction and demolition waste, industrial by-products, and geopolymers in concrete mixtures for 3D printing applications. Particular attention is given to pozzolanic activity, particle size effects, mechanical strength, rheology, thermal conductivity, and fire resistance of recycled-based composites. The environmental assessment is considered through life-cycle analysis (LCA), emphasizing carbon footprint reduction strategies enabled by recycled constituents and low-clinker formulations. The analysis demonstrates that recycled-based 3D printable concretes can maintain or enhance structural performance while mix-level (cradle-to-gate, A1–A3) LCAs of printable mixes report CO₂ reductions typically in the range of ~20–50% depending on clinker substitution and recycled constituents—with up to ~48% for fine recycled aggregates when accompanied by cement reduction and up to ~62% for mixes with recycled concrete powder, subject to preserved printability. This work highlights both opportunities and challenges, outlining pathways for advancing durable, energy-efficient, and environmentally responsible 3D-printed construction materials. Full article

Municipal solid waste (MSW) disposal is one of the areas of sustainability development of modern countries including the Republic of Kazakhstan. Annually, more than 4 million tons of MSW are generated, and this amount continues to grow. Additionally, approximately 120 million tons of waste have already accumulated in landfills across the country. It is essential to select an MSW disposal technology that is environmentally friendly, minimizes the generation of more hazardous waste, and maximizes energy efficiency. Ideally, the technology should not only reduce energy consumption but also generate energy and valuable by-products that have market demand. The aim of this study is to conduct experimental research to evaluate the efficiency and environmental impact of incinerating both unsorted and sorted municipal solid waste. As a result of the experiment, the volumes of flue gases and the concentrations of harmful substances produced by the combustion of both unsorted and sorted waste were determined. Additionally, an analysis of the slag and ash generated from the combustion of sorted MSW was conducted. The obtained results enable the development of a waste-free technological scheme for a plant designed for the complete utilization of municipal solid waste. Full article

The escalating accumulation of industrial solid wastes (e.g., copper slag: CS, ground-granulated blast furnace slag: GGBS) and carbon-intensive cement production has intensified environmental challenges, driving the demand for sustainable construction materials that synergize waste valorization with carbon sequestration. This study investigates the evaluation of the compressive strength, mineralogical evolution, and real-time CO₂ capture of the alkali-activated geopolymer composite materials by optimizing the mixed design of precursor materials (CS/GGBS ratio: 7/3) with MgO (0–10%) and coconut shell (CSB), peanut shell (PSB), and durian shell biochar (DSB) (0–3%). Results reveal that the 5% MgO addition achieves an 89.5% early-age compressive strength increase versus the MgO-free specimen. The compressive strength of the geopolymer composite could be further increased by a 1.5% dosage of DSB with an average pore size of 8.98 nm. In addition, the incorporation of an appropriate amount of porous biochar could not only enhance the CO₂ capture capacity of the geopolymer composite, but also further improve the CO₂ mineralization efficiency. The optimal formulation (5% MgO + 1.5% DSB) could mineralize 40.2 kg CO₂ per ton of solid waste at least. This work highlights a sustainable strategy for synchronizing industrial solid waste valorization with carbon-negative construction providing scalable CO₂ sequestration solutions. Full article

Nanostructural optimization is key to enhancing the performance of low-carbon cements. Supersulfated cement (SSC) is an eco-friendly, low-carbon cement primarily composed of blast furnace slag and calcium sulfate. This study investigates the effects of two types of crystalline anhydrite on the hydration degree and strength of SSC. The experiment used III ${\mathrm{C}\mathrm{a}\mathrm{S}\mathrm{O}}_4$ (high solubility) and II-U ${\mathrm{C}\mathrm{a}\mathrm{S}\mathrm{O}}_4$ (low solubility) as sulfate activators, evaluating the mechanical properties of anhydrite produced at different calcination temperatures through an analysis of pore structure, phase composition, reaction degree of mineral powder, and hydration heat. The results indicate that II-U anhydrite enhances slag hydration, reduces pore size, and significantly improves the compressive strength of SSC. This improvement is attributed to its impact on slag hydration: it reduces gypsum consumption rate, delays ettringite formation, promotes gel product formation, decreases the volume ratio of ettringite to calcium silicate hydrate (C-S-H) gel, fills pores, and decreases porosity. This study reveals the influence of calcined dihydrate gypsum phase changes on the macroscopic properties of SSC and the microstructure of hydration, elucidating the hydration mechanism of anhydrite-based SSC. This work provides a nanomaterial-based strategy for SSC design via crystal phase engineering. Full article

The construction industry is a major contributor to global environmental impacts, particularly through the production and use of cement-based materials. In response to this challenge, this study provides a comprehensive synthesis of recent advances in the integration of Life-Cycle Assessment (LCA) and Artificial Neural Networks (ANNs) for optimizing cementitious composites containing Supplementary Cementitious Materials (SCMs). A total of 14 case studies specifically addressing this topic were identified, reviewed, and analyzed, spanning various binder compositions, ANN architectures, and LCA frameworks. The findings highlight how hybrid ANN–LCA systems can accurately predict mechanical performance while minimizing environmental burdens, supporting the formulation of low-carbon, high-performance cementitious composites. The diverse SCMs explored, including fly ash, slag, silica fume, waste glass powder, and rice husk ash, demonstrate significant potential for reducing CO₂ emissions, energy consumption, and raw material depletion. Furthermore, the systematic comparative matrix developed in this work offers a valuable reference for researchers and practitioners aiming to implement intelligent, eco-efficient mix designs. Overall, this study contributes to advancing digital sustainability tools and reinforces the viability of ANN–LCA integration as a scalable decision-support framework for green construction practices. Full article

Phosphogypsum represents a gypsum-based solid waste originating from phosphoric acid production, which can be exploited for road filling after cement modification. This study delved into the composition design of high-volume phosphogypsum road base materials, aiming to ascertain their feasibility for subgrade filling, and refine the mix ratio. The main content of phosphogypsum was set at three high-proportion intervals of 86%, 88% and 90%, while the total content of inorganic curing agent was fixed at 0.5% of the total material. Within such a total amount, the proportion of bentonite was preserved at 20%, whereas the proportion of waterproofing agent was configured at three gradients of 20%, 25% and 30%, with the remaining part supplemented by powdered sodium silicate. Merged with trace amounts of inorganic curing agents, particularly the waterproofing agent component, the composite cementitious system comprising cement and ground granulated blast-furnace slag (GGBS) was leveraged to augment the key road performance and water stability of high-volume phosphogypsum-based materials. Material strengths were observed to be distinguishable under an array of phosphogypsum contents, which could be explained by the varying proportions of cement, GGBS and waterproofing agent. The test samples and microscopic products were dissected via XRD and SEM, demonstrating that the hydration products of the materials were predominantly C-S-H gel and ettringite crystals. Full article