Search Results (159)

In societies worldwide, there is significant pressure on the construction industry to employ waste/recycled materials instead of natural-sourced materials to develop infrastructures to mitigate negative environmental consequences. This study investigated the feasibility of using waste pumice powder as a binder in place of granular blast-furnace slag to manufacture geopolymer concrete. Three sets of GC mixes were developed with three ratios of alkaline activator/binder (A/B) of 0.45, 0.5, and 0.55. Eight GC mixes were prepared for each set, with eight replacement ratios of GGBFS with WPP (0%, 30%, 50%, 60%, 70%, 80%, 90%, and 100%). The influence of WPP addition as a substitute source of aluminosilicate precursors on the fresh (workability and setting time), mechanical (compressive strength and flexural strength), physical characteristics (density and water absorption), and microstructure morphology of WPP/slag-based geopolymers were studied. A linear correlation between UPV and compressive strength was found. The results revealed that setting times and workability are affected by the A/B ratio and content of WPP. WPP reduces the workability and increases setting time (both initial and final). There was a drop in compressive and flexural strengths as the percentage of WPP in the GC increased. The maximum compressive (60 MPa) and flexural strength (4.96 MPa) at an A/B ratio of 0.45 for a 100% slag content mix were obtained. However, a GC mix containing 50% WPP and 50% slag with a compressive strength of 28 MPa after 28 days of curing at ambient temperature was achieved, which is acceptable for structural applications. Full article

Engineered geopolymer composite (EGC) is a high-performance material with enhanced mechanical and durability capabilities. Ground granulated blast furnace slag (GGBFS) and silica fume (SF) are common binder materials in producing EGC. However, due to the scarcity and high cost of these materials in some countries, sustainable alternatives are needed. This research focused on producing eco-friendly EGC made of cheaper and more common pozzolanic waste materials that are rich in aluminum and silicon. Rice husk ash (RHA), granite waste powder (GWP), and volcanic pumice powder (VPP) were used as partial substitutions (10–50%) of GGBFS in EGC. The effects of these wastes on workability, unit weight, compressive strength, tensile strength, flexural strength, water absorption, and porosity of EGC were examined. The residual compressive strength of the proposed EGC mixtures at high elevated temperatures (200, 400, and 600 °C) was also evaluated. Additionally, scanning electron microscope (SEM) was employed to analyze the EGC microstructure characteristics. The experimental results demonstrated that replacing GGBFS with RHA and GWP at high replacement ratios decreased EGC workability by up to 23.1% and 30.8%, respectively, while 50% VPP improved EGC workability by up to 38.5%. EGC mixtures made with 30% RHA, 20% GWP, or 10% VPP showed the optimal results in which they exhibited the highest compressive, tensile, and flexural strengths, as well as the highest residual compressive strength when exposed to high elevated temperatures. The water absorption and porosity increased by up to 106.1% and 75.1%, respectively, when using RHA; increased by up to 23.2% and 18.6%, respectively, when using GWP; and decreased by up to 24.7% and 22.6%, respectively, when using VPP in EGC. Full article

Various studies have reported the use of alkali-activated composites to enable sustainable development in the construction industry as these composites eliminate the need for cement. However, few studies have used ferronickel slag aggregates (FSAs) as an aggregate material for alkali-activated composites. Alkali-activated composites are environmentally friendly and sustainable construction materials that can reduce carbon dioxide emissions from cement production, which accounts for 7% of global carbon emissions. In the construction industry, various research was conducted to improve the performance of alkali-activated composites, such as changing the binder, alkali activator, or aggregate. However, research on the application of ferronickel slag aggregate as an aggregate in alkali-activated composites is still insufficient. In addition, the effect of ferronickel slag aggregate on the performance of alkali-activated composites when using calcium-based or sodium-based alkali activators has not been reported yet. Thus, this study prepared ground granulated blast-furnace slag-based alkali-activated composites with 0, 10, 20, and 30% FSA as natural fine aggregate substitutes. Then, the fluidity, micro-hydration heat, compressive strength properties, and resistance to chloride ion penetration of the alkali-activated composite were evaluated. The test results showed that the maximum temperature of the CF10, CF20, and CF30 samples with FSA was 35.4–36.4 °C, which is 3.8–6.7% higher than that of the CF00 sample. The 7 d compressive strength of the sample prepared with CaO was higher than that of the sample prepared with Na₂SiO₃. Nevertheless, the 28 d compressive strength of the NF20 sample with Na₂SiO₃ and 20% FSA was the highest, with a value of approximately 55.0 MPa. After 7 d, the total charge passing through the sample with Na₂SiO₃ was approximately 1.79–2.24 times higher than that of the sample with CaO. Moreover, the total charge decreased with increasing FSA content. Full article

Hydrogen is increasingly recognized as a viable solution to meet the growing global energy demand, making large-scale hydrogen storage essential for successfully realizing a full-scale hydrogen economy. Geological formations, such as depleted oil and gas reservoirs, salt caverns, and aquifers, have been identified as potential storage options. Additionally, unconventional methods like manufactured lined rock caverns and abandoned coal mines are gaining interest. This study introduces polymerized sulfur concrete (PSC) as a promising alternative to replace the current construction systems, which rely on Portland cement concrete and lining materials like stainless steel or polypropylene plastic liners. The paper presents the formulation of PSC, optimization of its compositional design, and evaluation of its physico-mechanical-chemical properties. The results demonstrate that PSC offers excellent mechanical strength, chemical resistance, and low permeability, making it highly suitable for underground hydrogen storage in lined rock caverns. The results showed that the manufactured PSC exhibits excellent physicochemical properties in terms of compressive strength (35–58 MPa), density (2.277–2.488 g/cm³), setting time (30–60 min), curing time (24 h), air content (4–8%), moisture absorption potential (0.17–0.3%), maximum volumetric shrinkage (1.69–2.0%), and maximum service temperature (85–90 °C). Moreover, the PSC is nonconductive and classified with zero flame spread classification and fuel contribution. In addition, the SPC was found to be durable in harsh environmental conditions involving pressure, humidity, and pH variations. It is also capable of resisting corrosive environments. In addition, the statistical modeling indicates that an overall mixture proportion of 32.5 wt.% polymerized sulfur, 32.5 wt.% dune sands, 17.5 wt. % LFS, and 17.5 wt.% GGBFS appear optimal for density values ranging from 2.43 to 2.44 g/cm³ and compressive strength ranging from 52.0 to 53.2 MPa, indicating that the PSC can sustain formation pressure up to about 5.3 km below the ground surface. Therefore, by addressing the critical limitations of traditional materials, PSC proves to be a durable, environmentally sustainable solution for lined rock caverns, reducing the risk of hydrogen leakage and ensuring the integrity of storage systems. Full article

Alkali-activated binders have emerged as promising alternatives to Ordinary Portland Cement (OPC) due to their sustainability features and potential advantages. This study evaluates the durability properties of heat-cured fly ash (FA) and ground granulated blast-furnace slag (GGBFS) geopolymer mortars activated with sodium hydroxide, which were subjected to wet–dry cycling in saline environments. Three series of FA, a FA/GGBFS blend, and GGBFS mortars previously optimized on a compressive strength basis were investigated and compared against two control OPC mixes. Performance indicators such as the water absorption, porosity, flexural strength, and compressive strength were analyzed. The results demonstrate that geopolymer mortars have significantly reduced water absorption and porosity with increasing wet–dry cycles. The compressive strength of the FA/GGBFS mortars also increased from 66.5 MPa (untreated) to 87.9 MPa over 45 cycles. The flexural strength remained stable or improved slightly across all geopolymer mortars. The control OPC specimens experienced significant deterioration, with compressive strength in CEM I 42.5R dropping from 51.8 to 17.1 MPa. These findings highlight the superior durability of geopolymer mortars under harsh saline conditions, demonstrating their potential as a resilient alternative for coastal and marine structures. Full article

Low-cost and high-performance materials or techniques that could synergistically remove phenanthrene (PHE) in a simple manner were highly desired. Herein, we reported an alkali-activated slag (AAS) that proved applicable in both construction and environmental protection efforts. AAS was synthesized by mixing ground granulated blast furnace slag (GGBFS) and an alkaline solution. The prepared AAS mortar achieved the highest mechanical strength when using an alkaline activator with a Na₂O concentration of 8% by slag weight. Moreover, AAS exhibited excellent sorption performance towards PHE, with the highest sorption performance reaching 44.0 mg/g, which was much higher than that of GGBFS. Sorption of PHE reached equilibrium within approximately 120 h and fit well with the pseudo-second-order model. Furthermore, the primary sorption mechanisms for PHE on AAS were attributed to cation-π interactions, hydrogen bonding, and flocculation. The strategy of using AAS not only met the requirements for high-performance and low-cost materials but also addressed the challenging issues of developing an all-in-one treatment for PHE pollutants, which was of great significance to wastewater purification. Full article

This study presents the durability, strength and microstructure of non-heat-cured geopolymer mortars (GMs) containing metakaolin (MK), ground granulated blast furnace slag (GGBFS), potassium hydroxide (KOH), sodium metasilicate (Na₂SiO₃), CEN sand and network water. Optimum MK, GGBFS and activator solution ratios were investigated, and the compressive strength of non-heat-cured 28-day GMs reached 55 MPa. Analysis of GMs using scanning electron microscopy (SEM), energy-dispersive X-ray spectrophotometry (EDX) and X-ray powder diffraction (XRD) revealed alumino-silicate formation, potassium from KOH solution and calcium from GGBFS. It showed that the grains containing high silica in the form of quartz crystals were found in the gel formation. The strength and durability of MK- and GGBFS-based GMs exposed to freeze–thawing, a high temperature, wear loss, magnesium sulfate (MgSO₄), sodium sulfate (Na₂SO₄) and HCl solutions were found to be sufficient. Full article

The cement industry is known for being highly energy-intensive and a significant contributor to global CO₂ emissions. To address this environmental challenge, this study explores the potential of using the waste materials of steel slag (SS) and eggshell powder (ESP) as partial replacements for cement in alkali-activated mortars (AAMs) production, activated by NaOH and Na₂SiO₃. Mortar samples are prepared with 50% of ordinary Portland cement (OPC) as part of the total binder, and the remaining 50% is composed of ESP, incrementally replaced by SS at levels of 10%, 20%, 40%, and 50%. The activation process was performed with an 8% NaOH concentration and a silica modulus of 2. Key findings include that the workability of AAMs decreased with increasing SS content, requiring admixtures like superplasticizers or additional water to maintain workability. At 50% SS replacement, the water consistency and slump flow values were 32.56% and 105.73 mm, respectively, with a setting time reduction of approximately 36%, losing plasticity within 2 h. Both absorption capacity and porosity decreased as SS content increased from 10% to 50% of ESP. Additionally, the bulk density, compressive strength, and uniformity of the hardened mortar samples were enhanced with higher SS content, achieving maximum compressive strength (28.53 MPa) at 50% SS replacement after 56 days of curing. Furthermore, OPC-based AAMs incorporating SS and ESP demonstrate good resistance to sulfate attack and thermal heating. Microstructural analysis reveals the presence of C–S–H, C–A–S–H, and N–A–S–H phases, along with minor amounts of unreacted particles, and the microstructure shows a dense, highly compacted, and homogeneous morphology. These findings suggest that replacing eggshell powder with up to 50% steel slag enhances the hardened properties of AAMs. Further research is recommended to explore cement-free alkali-activated granular ground blast furnace slag (GGBFS) with ESP for more sustainable construction solutions. Full article

By reutilizing industrial byproducts, inorganic cementitious alkali-activated materials (AAMs) contribute to reduced energy consumption and carbon dioxide (CO₂) emissions. In this study, coal gangue (CG) blended with ground granulated blast furnace slag (GGBFS) was used to prepare AAMs. The research focused on analyzing the effects of the GGBFS content and alkali activator (i.e., Na₂O mass ratio and alkali modulus [SiO₂/Na₂O]) on the mechanical properties and microstructures of the AAMs. Through a series of spectroscopic and microscopic tests, the results showed that the GGBFS content had a significant influence on AAM compressive strength and paste fluidity; the optimal replacement of CG by GGBFS was 40–50%, and the optimal Na₂O mass ratio and alkali modulus were 7% and 1.3, respectively. AAMs with a 50% GGBFS content exhibited a compact microstructure with a 28 d compressive strength of 54.59 MPa. Increasing the Na₂O mass ratio from 6% to 8% promoted the hardening process and facilitated the formation of AAM gels; however, a 9% Na₂O mass ratio inhibited the condensation of SiO₄ and AlO₄ ions, which decreased the compressive strength. Increasing the alkali modulus facilitated geopolymerization, which increased the compressive strength. Microscopic analysis showed that pore size and volume increased due to lower Na₂O concentrations or alkali modulus. The results provide an experimental and theoretical basis for the large-scale utilization of AAMs in construction. Full article

The global challenge faced due to the impact of the construction industry on climate change, along with the issues surrounding sustainable waste disposal, has necessitated various research on using waste products as eco-friendly alternatives in construction. In this study, the avoidance of waste disposal through landfills in Australia was encouraged by incorporating lime kiln dust (LKD) and tire rubber waste (TRW) into masonry mixes to manufacture green bricks. Furthermore, the investigations in this article highlight the use of mercury intrusion porosimetry (MIP) to determine the durability of the LKD-TRW bricks when exposed to freeze–thaw (F-T) cycles by examining the pore size distribution within the bricks. The LKD waste was blended with ground granulated blast furnace slag (GGBFS) at a 70:30 blending ratio and combined with the TRW in stepped increments of 5% from 0 to 20% to produce these eco-friendly bricks. The compressive strength (CS), flexural strength (FS), frost resistance (FR), pore size distribution according to mercury intrusion porosimetry (MIP), and the water absorption (WA) properties of the bricks were assessed. The CS and FS values at 28 days of curing were recorded as 6.17, 5.25, and 3.09 MPa and 2.52, 2, and 1.55 MPa for 0, 5, and 10% TRW contents, respectively. Durability assessments using the F-T test showed that the bricks produced with 0% TRW passed as frost-resistant bricks. Furthermore, the results from the MIP test showed a total pore volume of 0.033 mL/g at 3 µm pore size for the 0% TRW content, further confirming its durability. Hence, the 0% LKD-TRW bricks can be utilized in cold regions where temperatures can be as low as −43 °C without deteriorating. Lastly, WA values of 7.25, 11.76, and 14.96% were recorded for the bricks with 0, 5, and 10% TRW, respectively, after the 28-day curing period. From all of the results obtained from the laboratory investigations, the LKD-TRW bricks produced with up to 10% TRW were within the satisfactory engineering requirements for masonry units. Full article

Supplementary cementitious materials (SCMs) are eco-friendly cementitious materials that can partially replace ordinary Portland cement (OPC). The occurrence of early-age cracking in OPC-SCM blended cement is a significant factor impacting the mechanical properties and durability of the concrete. This article presents a comprehensive review of the existing research on cracking in OPC-SCM concrete mix at early ages. To assess the effects of SCMs on the early-age cracking of concrete, the properties of blended cement-based concrete, in terms of its viscoelastic behavior, evolution of mechanical performance, and factors that affect the risk of cracking in concrete at early ages, are reviewed. The use of SCMs in OPC-SCM concrete mix can be an effective method for mitigating early-age cracking while improving the properties and durability of concrete structures. Previous research showed that the shrinkage and creep of OPC-SCM concrete mix are lower than those of conventional concrete. Moreover, the lower cement content of OPC-SCM concrete mix resulted in a better resistance to thermal cracking. Proper selection, proportioning, and implementation of SCMs in concrete can help to optimize the performance and reduce the environmental impact of OPC-SCM concrete mix. Full article

In this study, natural fine aggregates (NFAs) in high-strength fly ash (FA)/ground granulated blast furnace slag (GGBFS)-based geopolymer concretes were both partially and completely replaced by RFAs to prepare geopolymer recycled fine aggregate concrete (GRFC). Herein, the impacts of RFA content (0%, 25%, 50%, 75%, and 100%) on the fresh and hardened performance and microstructural characteristics of a GRFC were investigated. The results indicated that with increasing RFA substitution ratio, the setting time of the GRFC decreases. In addition, the compressive strength and elastic modulus decrease. However, owing to the enhanced adhesion of the geopolymer matrix and recycled aggregate, RFA has a relatively small impact on the compressive strength, with a maximum strength loss of 9.7% at a replacement level of 75%. When the RFA content is less than 75%, the internal structure of the concrete remains relatively compact. The incorporation of RFA in concrete has been found to adversely affect its compressive strength and elastic modulus, while simultaneously increasing its brittleness. The increase in dosage of RFA leads to a reduction in the compressive strength and elastic modulus of concrete, while partial failure occurs when the GRFC constitutes 100% of the RFA. The existing stress–strain model for conventional concrete is recalibrated for the GRFC. Observed by SEM, with increasing RFA, the damage is mainly concentrated at the interface associated with the attached cement. Although the recalibrated model predicts the stress–strain responses of the GRFC reasonably well, an acceptable range of deviation is present when predicting the residual stress due to the relatively high strength and brittle behavior of the GRFC during compression. Through this research, the applicability of RFA is expanded, making it feasible to apply large quantities of this material. Full article

The global focus on geopolymer binder production has increased due to the adoption of waste materials and industrial byproducts. Given the gradual decline in the availability of fly ash and ground granular blast furnace slag (GGBFS) resulting from the decarbonization process in electricity and steel production, waste clay brick powder (WCBP) could be a viable substitute for these pozzolanic by-products. This study presents the economic and environmental benefits of the use of WCBP as a replacement for conventional pozzolanic by-products in geopolymer binder production by assessing its techno-eco-efficiency, environmental impact, and cost-effectiveness performances. The favorable mechanical characteristics exhibited by the fly ash–GGBFS–WCBP-based geopolymer binder emphasize the importance of assessing its sustainability alongside its technical viability. The study employed life cycle analysis (LCA), following ISO framework, and using the Simapro software 9.2, to evaluate the environmental implications of the use of WCBP-based geopolymer mixtures. Human toxicity emerged as the primary impact. Moreover, the analysis of life cycle costs highlighted key financial factors, with around 65–70% attributed to alkaline activators of the total cost. The production of alkaline activators was identified as a critical point for both environmental impact and economic considerations due to energy consumption. While WCBP-rich samples exhibit a 1.7–0.7% higher environmental impact compared to the control mix (CM), their high mechanical strength and cost-effectiveness make them technologically and economically efficient geopolymer mixes. In conclusion, the portfolio analysis for techno-eco-efficiency affirms that mixes containing 40%, 30%, and 20% WCBP are more efficient than those using 10% and 0% WCBP, respectively. Full article

Geopolymers (GPs) are gaining prominence due to their low carbon emissions and sustainable attributes. However, one challenge with GPs, particularly those made with ground granulated blast furnace slag (GGBFS), is their significant shrinkage during the geopolymerization process, limiting its practical applicability. This study focuses on how the substitution ratio of metakaolin (MK) and the concentration of sodium hydroxide (NaOH) in the activator can influence the shrinkage and strength of a GGBFS-based GP. The experimental approach employed a 3 × 3 parameter matrix, which varied MK substitution ratios (0%, 50%, and 100%) and adjusted the NaOH concentration (6 M, 10 M, and 14 M). The results revealed that increasing MK substitution, particularly with 6 M NaOH activation, reduced the GP shrinkage but also diminished compressive strength, requiring higher NaOH concentrations for strength improvement. Statistical tools, including analysis of variance (ANOVA) and second-order response surface methodology (RSM), were employed for analysis. ANOVA results indicated the significant impacts of both the MK content and NaOH concentration on compressive strength, with no observable interaction. However, the shrinkage exhibited a clear interaction between MK content and NaOH concentration. The RSM model accurately predicted compressive strength and shrinkage, demonstrating a high predictive accuracy, for which the coefficients of determination (R²) were 0.99 and 0.98, respectively. The model provides a reliable method for determining the necessary compressive strength and shrinkage for GGBFS-based GP based on MK substitution and NaOH concentration. Within the optimization range, the RSM model compared with experimental results showed a 6.04% error in compressive strength and 0.77% error in shrinkage for one interpolated parameter set. This study establishes an optimized parameter range ensuring a GP performance that is comparable to or surpassing OPC, with a parameter set achieving a compressive strength of 34.9 MPa and shrinkage of 0.287% at 28 days. Full article

The continuous growth of industrial solid waste production has generated many environmental problems. We evaluated the potential of industrial solid waste as a substitute filler in asphalt mastic, with the aim of increasing the use of sustainable road construction materials. In this study, X-ray fluorescence spectroscopy (XRF) and scanning electron microscopy (SEM) were used to characterize the oxide composition and micromorphology of limestone (LS), red mud (RM), steel slag (SS), and ground granulated blast-furnace slag (GGBFS). Four asphalt mastics containing LS, RM, SS, and GGBFS with a filler-to-binder weight ratio of one were prepared. An evaluation of the rheology and wetting of the solid-waste-filler asphalt mastic was conducted using a frequency sweep, temperature sweep, linear amplitude sweep (LAS), multiple stress creep and recovery (MSCR), and surface free energy (SFE) methods. The results showed that SS increased the complex modulus, elastic component of the asphalt mastic and decreased the nonrecoverable creep compliance at stress levels of 0.1 and 3.2 kPa, which improved the rutting resistance of the asphalt mastic and reduced deformation under high-temperature conditions. The RM and GGBFS increased the fatigue performance of the asphalt mastic under strain loading, enhanced its fatigue life, and maintained good performance under long-term loading. The dispersive component of the SFE parameter of the solid-waste-filler asphalt mastic was larger than the polar component for the largest share of the surface energy composition. The SFE of the asphalt mastic prepared from the industrial solid-waste filler was reduced; however, the difference was insignificant compared to the limestone asphalt mastic. Solid-waste-filler asphalt mastic has performance characteristics, and its actual application can be based on different performance characteristics to select an appropriate solid-waste filler. The results of this study provide new technological solutions for solving the utilization rate of solid waste materials and sustainable road construction in the future. Full article