Search Results (100)

The study investigates the potential of enhancing gypsum board properties through the integration of hemp hurds and glass fibers. The investigation focuses on evaluating the composite material’s density, water absorption, flexural strength, compressive strength, and thermal performance. Experimental results demonstrate a reduction in gypsum composite density and improved thermal insulating properties with the introduction of hemp hurds. Water absorption, a significant drawback of gypsum boards, is mitigated with hemp hurds, indicating potential benefits for insulation efficiency. For mechanical tests, the gypsum ceiling board at approximately 5% by weight exhibits a flexural strength value exceeding the minimum average threshold of 1 MPa and the highest average compressive strength at 2.94 MPa. Thermal testing reveals lower temperatures and longer time lags in gypsum boards with 5% hemp hurds, suggesting enhanced heat resistance and reduced energy consumption for cooling. The study contributes valuable insights into the potential use of hemp hurds in gypsum-based building materials, presenting a sustainable and energy-efficient alternative for the construction industry. Full article

To address the practical limitations of conventional alkaline activators (e.g., handling hazards, cost) and promote the resource utilization of industrial solid wastes, this study developed a novel all-solid-waste activator system comprising soda residue (SR) and carbide slag (CS). The synergistic effects of SR-CS activators on the hydration behavior of blast furnace slag (GGBS)–fly ash (FA) cementitious composites were systematically investigated. Mechanical performance, phase evolution, and microstructural development were analyzed through compressive strength tests, XRD, FTIR, TG-DTG, and SEM-EDS. Results demonstrate that in the SR-CS activator system, which combines with desulfuriation gypsum as sulfate activator, increasing CS content elevates the normal consistency water demand due to the high-polarity, low-solubility Ca(OH)₂ in CS. The SR-CS activator accelerates the early hydration process of cementitious materials, shortening the paste setting time while achieving compressive strengths of 17 MPa at 7 days and 32.4 MPa at 28 days, respectively. Higher fly ash content reduced strength owing to increased unreacted particles and prolonged setting. Conversely, desulfurization gypsum exhibited a sulfate activation effect, with compressive strength peaking at 34.2 MPa with 4 wt% gypsum. Chloride immobilization by C-S-H gel was confirmed, effectively mitigating environmental risks associated with SR. This work establishes a sustainable pathway for developing low-carbon cementitious materials using multi-source solid wastes. Full article

This study investigates the use of gypsum waste from civil construction as a partial substitute for cement in soil–cement formulations, aiming to produce eco-friendly bricks aligned with circular economy principles. Formulations were prepared using a 1:8 cement–soil ratio, with gypsum replacing cement in proportions ranging from 5% to 40%. The raw materials were characterized in terms of chemical composition, crystalline phases, plasticity, and thermal behavior. Specimens, molded by uniaxial pressing into cylindrical bodies and cured for either 7 or 28 days, were evaluated for compressive strength, water absorption, durability, and microstructure. Water absorption remained below 20% in all samples, with an average value of 16.20%. Compressive strength after 7 days exhibited a slight reduction with increasing gypsum content, ranging from 16.36 MPa (standard formulation) to 13.74 MPa (40% gypsum), all meeting the quality standards. After 28 days of curing, the formulation containing 10% gypsum achieved the highest compressive strength (26.7 MPa), surpassing the reference sample (25.2 MPa). Mass loss during wetting–drying cycles remained within acceptable limits for formulations incorporating up to 20% gypsum. Notably, samples with 5% and 10% gypsum demonstrated superior mechanical performance, while the 20% formulation showed performance comparable to the standard formulation. These findings indicate that replacing up to 20% of cement with gypsum waste is a technically and environmentally viable approach, supporting sustainable development, circular economy, and reduction of construction-related environmental impacts. Full article

This study investigates the industrial potential of red gypsum (RG), a major by-product of titanium dioxide (TiO₂) production, for the development of thermoplastic polypropylene (PP)-based composites via melt extrusion, targeting agricultural applications. Prior to compounding, RG was thermally treated at approximately 200 °C to remove residual moisture and chemically bound water, resulting in its anhydrous form (CaSO₄). PP/RG composites were then formulated with RG loadings up to 20 wt.%, employing stearic acid (SA) as a compatibilizer. The resulting materials were thoroughly characterized and successfully processed through industrial-scale injection molding up to 250 °C. Morphological and FTIR analyses confirmed the role of SA in enhancing both filler dispersion and interfacial adhesion between RG and the PP matrix. SEM images revealed finer and more uniformly distributed RG particles, resulting in a reduced loss of ductility and elongation at break typically associated with filler addition. Specifically, the Young’s Modulus increased from 1.62 GPa (neat PP) up to 3.21 GPa with 20 wt.% RG and 0.6 wt.% SA. The addition of 0.6 wt.% SA also helped limit the reduction in stress at break from 46.68 MPa (neat PP) to 34.05 MPa and similarly mitigated the decrease in Charpy impact energy, which declined slightly from 2.66 kJ/m² (neat PP) to 2.24 kJ/m² for composites containing 20 wt.% RG. Preliminary phytotoxicity was assessed using germination tests on Lepidium sativum L. seeds. Eluates from both untreated and SA-treated RG powders resulted in germination indices below 80%, indicating phytotoxicity likely due to high sulfate ion concentrations. In contrast, eluates from composite pellets exhibited germination indices equal to or exceeding 100%, demonstrating the absence of phytotoxic effects. These results highlight the suitability of the developed composites for applications in floriculture and horticulture. The optimized composite pellets were successfully processed via injection molding to manufacture plant pots, which exhibited a dark brown coloration, confirming the effective pigmenting function of RG. These results demonstrate the potential of red gypsum to serve both as a functional filler and pigment in PP composites, providing a sustainable alternative to iron oxide pigments and promoting the valorization of industrial waste through resource recovery. Full article

This study investigates the performance of alkali-activated mortar incorporating slag, fly ash, and desert sand, with a focus on flowability, mechanical properties, sulfate resistance, and microstructural characteristics. A four-factor, three-level orthogonal experimental design was used to analyze the effects of the fly ash substitution rate, alkali content (Na₂O/b), activator modulus, and desert sand replacement rate for natural sand. The results indicate that increased slag and desert sand contents reduce mortar flowability. Despite this, the mortar exhibits excellent mechanical strength, with compressive strength reaching 77.7 MPa at 28 days and increasing to 89.34 MPa under sulfate exposure. However, after 120 days of sulfate erosion, a decline in strength is observed due to the formation of expansive products such as gypsum and caliche, leading to cracking. Microstructural analyses (XRD, SEM/EDS, MIP) reveal partial dissolution of desert sand under alkali activation, enhancing gel formation and reducing cumulative porosity. The pore structure predominantly consists of harmless pores. These findings demonstrate the potential of slag–fly ash–desert sand alkali-activated mortar as a durable and sustainable material for structural and construction engineering applications, especially in sulfate-rich environments or arid regions where desert sand is abundant. Full article

Solid waste-based cementitious materials (SWBC) are composed of steel slag (SS), granulated blast furnace slag (GBFS), fly ash (FA), desulfurization gypsum (DG), and Portland cement (PC). Currently, SWBC holds great potential as a sustainable building material; however, its low early compressive strength and volume expansion limit its range of application. Therefore, the main objective of this study is to enhance the mechanical properties and dimensional stability of SWBC by adding nano-SiO₂, while also improving its resistance to chloride ions, thereby promoting its use in the field of sustainable building materials. A comprehensive experimental approach integrating mechanical performance testing, shrinkage analysis, and chloride diffusion coefficient evaluation was established, with the testing methods of thermogravimetric analysis-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The study found that adding nano-SiO₂ enhanced the nucleation of calcium silicate hydrates (C-S-H) gel in hydrated SWBC, leading to improved compressive strength and reduced chloride permeability when SiO₂ addition was 0.5%. When the hydration period extends to 28 days, the modified SWBC achieves a compressive strength of 56 MPa. However, excessive nano-SiO₂ (≥1%) inhibited the long-term hydration of SWBC but had no significant effect on the final compressive strength. Full article

This study demonstrated the effectiveness of using autoclaved aerated concrete AAC waste as a low-cost filtering material for removing hydrogen sulfide (H₂S) from gas streams. A long-term experiment (89 days) was conducted in a packed bed reactor to purify synthetic biogas composed of N₂, CO₂, H₂S, and O₂. Optimal H₂S removal efficiencies, reaching up to 100%, were achieved under highly acidic conditions (pH ≈ 1–3) and low oxygen concentrations (<1%). In the presence of oxygen, calcium oxides in the AAC waste react with H₂S to form gypsum (CaSO₄ 2H₂O). The simultaneous removal of both oxygen and H₂S by AAC waste, following an approximate 2:1 molar ratio, may be particularly beneficial for biogas streams containing unwanted traces of oxygen. The transformation and lifespan of AAC waste were monitored through sulfur accumulation in the material and pressure drop measurements, which indicated structural changes in the AAC waste. At the end of its lifespan, the AAC waste exhibited an H₂S removal capacity of 185 g_H2S kg_AAC⁻¹. This innovative and sustainable process not only provides a cost-effective and environmentally sound solution for the simultaneous removal of H₂S and O₂ from biogas, but also promotes waste valorization and aligns with circular economy principles. Full article

In 2022, the building sector accounted for 30% of global energy demand and 27% of CO₂ emissions, of which approximately 9% came from building material production. To mitigate this impact, it is critical to develop sustainable alternatives that reduce the environmental footprint of construction materials. This paper presents an original study where the effect of coconut fibre as a reinforcing material in gypsum composites is analysed. These plant-based fibres reduce the composite’s density, improve thermal behaviour, and integrate circular economy criteria in construction. In this way, a physico-mechanical characterisation of these novel gypsum-based composites is addressed, and their potential application for developing prefabricated slabs is innovatively explored. Composites were prepared with coconut fibre incorporation in volume up to 17.5%, and mechanical and thermal properties and their behaviour under water action were evaluated. The results indicate that the fibre addition reduced density by about 10.0%, improved flexural strength by 20.5% and compressive strength by 28.4%, and decreased thermal conductivity by 56.3%, which increased the energy efficiency of the building facade by 7.8%. In addition, hydrophobic properties improved, reducing capillary absorption by 15.9% and open porosity by 3.3%. These findings confirm the technical feasibility of coconut fibre-reinforced plaster for application in prefabricated wall and ceiling elements, promoting the efficient use of natural resources and driving the development of sustainable building materials. Full article

In response to the need for sustainable soil stabilization alternatives, this study explores the use of waste materials and biopolymers to improve the mechanical behavior of clay from Cartagena, Colombia. Crushed limestone waste (CLW), ground glass powder (GG), recycled gypsum (GY), xanthan gum (XG), and the combination of XG with polypropylene fibers (XG–PPF) were used as stabilizing agents. Samples were compacted at different dry densities and cured for 28 days. Unconfined compressive strength (UCS) and ultrasonic pulse velocity (UPV) tests were conducted to assess the strength and stiffness of the treated mixtures. Results were normalized using the porosity/binder index ($\mathrm{\eta }/B_{iv}$), leading to predictive equations with high determination coefficients (R² = 0.94 for UCS and R² = 0.96 for stiffness). However, XG-treated mixtures exhibited distinct behavior that prevented their inclusion in a unified predictive model, as the fitted exponent x in the porosity/binder index ($\mathrm{\eta }/B_{iv}^x$) differed markedly from the others. While an exponent of 0.28 was suitable for blends with mineral binders, the optimal x values for XG and XG–PPF mixtures were significantly lower at 0.02 and 0.03, respectively, reflecting their unique gel-like and fiber-reinforced characteristics. The analysis of variance (ANOVA) identified cement content and compaction density as the most influential factors, while some interactions involving the residues were not statistically significant, despite aligning with experimental trends. The findings support the technical viability of using sustainable additives to enhance soil properties with reduced environmental impact. Full article

Ultra-high-performance concrete (UHPC) is known for its outstanding strength and durability but is often limited by the high cost of traditional materials, like cement, fine aggregates, and silica fume. This review examines the use of industrial by-products—specifically, iron tailings, steel slag, and desulfurization gypsum—as sustainable alternatives in UHPC mix design. These materials serve as supplementary cementitious components and fine aggregates, helping reduce environmental impacts and production costs. This study highlights the synergistic hydration mechanisms between Portland cement and waste-based materials, leading to improved microstructure and long-term strength. The role of steel fibers in enhancing crack resistance is also discussed. Challenges related to workability, cost, and lack of standardization are addressed, along with opportunities for innovative mix designs, low-carbon binders, and 3D printing. Overall, this paper underscores the potential of industrial by-products to advance sustainable, high-performance UHPC solutions. Full article

To address the high carbon emissions and resource dependency associated with conventional ordinary Portland cement (OPC) production, this study systematically investigated the preparation processes, hydration mechanisms, and chemical properties of high-belite calcium sulfoaluminate (HBCSA) and calcium sulfoaluminate (CSA) cements based from industrial solid wastes. The results demonstrate that substituting natural raw materials (e.g., limestone and gypsum) with industrial solid wastes—including fly ash, phosphogypsum, steel slag, and red mud—not only reduces raw material costs but also mitigates land occupation and pollution caused by waste accumulation. Under optimized calcination regimes, clinkers containing key mineral phases (C₄A₃S⁻ and C₂S) were successfully synthesized. Hydration products, such as ettringite (AFt), aluminum hydroxide (AH₃), and C-S-H gel, were identified, where AFt crystals form a three-dimensional framework through disordered growth, whereas AH₃ and C-S-H fill the matrix to create a dense interfacial transition zone (ITZ), thereby increasing the mechanical strength. The incorporation of steel slag and granulated blast furnace slag was found to increase the setting time, with low reactivity contributing to reduced strength development in the hardened paste. In contrast, Solid-waste gypsum did not significantly differ from natural gypsum in stabilizing ettringite (AFt). Furthermore, this study clarified key roles of components in HBCSA/CSA systems; Fe₂O₃ serves as a flux but substitutes some Al₂O₃, reducing C₄A₃S⁻ content. CaSO₄ retards hydration while stabilizing strength via sustained AFt formation. CaCO₃ provides nucleation sites and CaO but risks AFt expansion, degrading strength. These insights enable optimized clinker designs balancing reactivity, stability, and strength. Full article

This study aims to enhance the sustainable utilization of electrolytic manganese residue (EMR), an industrial solid waste rich in sulfates and pollutants, by modifying it with appropriate proportions of granulated blast furnace slag (GBFS) and carbide slag (CS) and evaluating its potential as a cement retarder. The influence of both the GBFS/CS ratio and the dosage of modified EMR on the performance of cement mortar was systematically investigated, focusing on workability, mechanical properties, hydration behavior, leaching toxicity, and carbon emissions. Results showed that GBFS and CS significantly reduced pollutant concentrations in EMR while improving gypsum crystallinity. Modified EMR exhibited retarding properties, extending the initial and final setting times of cement mortar from 98 min and 226 min to 169 min and 298 min. With an 8 wt.% dosage, the 28-day compressive strength reached 58.76 MPa, a 1.3-fold increase compared to cement mortar (45.21 MPa). The content of reactive SiO₂, Al₂O₃, Ca(OH)₂, and CaSO₄·2H₂O promoted secondary hydration of cement and generated significant ettringite (AFt) and calcium silicate hydrate (C-S-H) gels, forming a dense microstructure. Pollutants in the modified EMR-cement mortar were reduced through precipitation, substitution, and encapsulation, meeting leaching toxicity standards. This study highlights the feasibility and environmental benefits of employing modified EMR as a cement retarder, demonstrating its potential in sustainable building materials. Full article

With the aim of reducing the environmental impact of buildings, the appropriate selection of building materials is essential, as a building is a complex system composed of various materials. With this background, a multi-criteria decision-making approach has recently gained traction. This study demonstrated the effect of building material selection on both environmental and economic parameters of a building in the context of Japan. A comparative analysis of five structural frame options was conducted utilizing a reference building model to assess the implication of material choices. The findings indicated that wooden frame options are advantageous in environmental aspects compared to non-wooden frames, provided that sustainable forestry practices and appropriate recycling scenarios are implemented. Conversely, it was found that a Cross Laminated Timber (CLT) frame is the most expensive option. This suggests that a hybrid approach, which combines various frame materials, could yield a more effective solution in terms of both environmental and economic sustainability. In addition, it was highlighted that building envelopes, such as foundation, exterior wall, and roof, should be prioritized to enhance the sustainability of a building from a material perspective. Furthermore, gypsum board, commonly used for sheathing building elements, should be selected with careful consideration of its environmental impact. Full article

The construction industry generates approximately 45% of the world’s total waste, highlighting the need for sustainable solutions. This study investigates the incorporation of quartzite waste (QW) and fiberglass waste (FW) into the production of gypsum plasterboard to reduce its environmental impact while maintaining its structural performance. The optimum formulation (MQ-20) was determined by replacing 20% of the gypsum with QW, based on the observed free water loss and crystallization water. The physical, mechanical, and thermal properties of the reference and modified boards were evaluated. The results showed that the MQ-20 samples exhibited a 30% reduction in flexural strength compared to the reference, while still exceeding regulatory standards. In addition, the MQ-20 samples had a lower thermal conductivity (0.54 W/(m∙K)) than the reference (0.58 W/(m∙K)). Fire-resistance tests showed that the inclusion of QW and FW reduced the size and number of cracks, improving the structural stability of the plasterboard at high temperatures. This research demonstrates that the incorporation of industrial waste into plasterboard is a viable and environmentally friendly approach, providing both mechanical and thermal performance benefits. These findings provide a basis for future studies aimed at developing sustainable building materials with improved functional properties. Full article

Cement-based self-leveling mortar (CSL) is a special building material that utilizes cement as the main cementitious component, combined with a variety of admixtures. Its self-leveling characteristics enable it to effectively level and fill uneven surfaces. Additionally, the innovative green CSL developed from industrial by-products can further enhance both environmental and economic benefits. This paper systematically reviews the use of admixtures and industrial by-products in the production of CSL. The main findings include the following: (i) compared to the international ISO standard, China’s standard JC/T 985 provides more detailed testing parameters regarding fluidity, mechanical properties, and shrinkage; (ii) the effect of additives on CSL is affected by its molecular weight and structure, and high molecular weight improving the workability of the additives; (iii) industrial by-products have been effectively incorporated into CSL, leading to a reduction in reduced greenhouse gas emissions and a decreased environmental impact; (iv) macro and microanalysis results of different green CSLs show that industrial by-product gypsum has the greatest potential for application in CSL. Based on these findings, this paper offers valuable reference data for the use of admixtures and industrial by-products in CSL. Furthermore, it contributes innovatively to the sustainable development of infrastructure construction. Full article