Search Results (215)

One-part geopolymer mortars provide an alternative to cementitious materials by using dry activators and industrial by-products. This study evaluated a multi-precursor matrix containing slag, fly ash, ceramic powder, red mud, and 5% MgO, reinforced with polyvinyl alcohol (PVA), basalt, or micro-steel fibers at 0.4% and 0.8% by volume. Specimens were cured at 20 ± 2 °C or at 80 °C for 24 h and assessed for flowability, mechanical properties, ultrasonic pulse velocity (UPV), Böhme abrasion, 24 h water absorption, and sorptivity. XRD, FTIR, and SEM/EDS were used only to compare by heat-cured mixtures. The results showed that at 28-day, heat curing increased compressive strength by 39.5–71.8%, flexural strength by 29.2–134.4%, and UPV by 20.5–36.4%, while reducing sorptivity by 12.2–35.7% relative to ambient curing. PVA reduced flowability likely because of its hydrophilic surface and high surface area. For 0.8PVA, the flow diameter was 23.6% below the reference, whereas the 28-day heat-cured flexural strength reached 7.5 MPa, with the lowest abrasion thickness loss of 0.63 mm. Micro-steel mixtures maintained compressive strength comparable to the reference, reaching 72–73 MPa at 28-day. Heat curing reduced water absorption in PVA and basalt mixtures, whereas the reference and micro-steel mixtures showed insignificant change. Microstructural analyses suggested the formation of a more compact and reacted aluminosilicate matrix under heat-cured conditions. A screening life-cycle assessment, limited to the non-fiber-reinforced reference matrix, showed that heat-curing increased global warming potential by 7.6%, while the two solid activators contributed approximately 45% of the ambient-cured reference GWP. The findings indicate that heat curing significantly enhances the performance of one-part geopolymers, while fiber selection provides additional mechanical and durability improvements. Full article

The growing use of PET strapping in packaging has increased plastic waste, prompting interest in its reuse in cement-based materials. This study evaluates waste PET strapping powder as a partial replacement for natural sand in cement mortar. Mortars were prepared with three water–cement ratios (0.4, 0.5, and 0.6) and four replacement levels (0%, 5%, 10%, and 15%). Slump, flow, compressive strength, flexural strength, ultrasonic pulse velocity (UPV), four-point resistivity, and sulphate resistance were examined at different curing ages. Increasing PET content reduced slump and flow, indicating lower workability. It also decreased compressive and flexural strengths, with flexural strength showing a greater reduction. UPV declined as PET replacement increased, which was attributed to the combined effects of acoustic-property contrast between PET and the cementitious matrix, interfacial wave scattering, and local microstructural defects. However, PET increased electrical resistivity and reduced sulphate-related weight loss, indicating lower continuity of ion-conducting pathways and potentially improved resistance to the transport of aggressive ions under the adopted test conditions. SEM observations showed limited interfacial defects at 5% PET, whereas higher contents produced a more porous interfacial transition zone. Overall, the mix with 5% PET and W/C = 0.5 showed the best balance of properties, supporting the reuse of PET strapping powder as a sustainable sand replacement. Full article

This study investigates the influence of wood fly ash (WFA) and wood bottom ash (WBA) as a partial replacement of Portland cement (PC) on the mechanical performance and durability of cement mortars. Mortar mixtures containing 20% WFA (FA-20) and 20% WBA (BA-20) were compared with a reference mixture (REF) using bending and compressive strength tests, ultrasonic pulse velocity (UPV), total water absorption (TWA), and durability tests such as alkali–silica reaction (ASR) and carbonation resistance. The results showed that BA-20 exhibited higher mechanical performance and a denser microstructure than FA-20, as confirmed by UPV and TWA. At 365 days, compressive strength reached 71.9 MPa for REF, 64.3 MPa for BA-20, and 43.7 MPa for FA-20. Durability results indicated that after 365 days, REF exhibited the highest ASR expansion (~0.50%), whereas the incorporation of wood ash reduced expansion to approximately 0.41% for FA-20 and 0.29% for BA-20. In terms of carbonation resistance, FA-20 showed the greatest accelerated carbonation depth (10–14 mm), while REF exhibited the lowest carbonation depth (~3 mm). The differences were attributed to PC dilution and microstructural variations affecting porosity and transport properties. WBA demonstrated better performance than WFA, highlighting the importance of wood ash particle characteristics in PC replacement applications. Full article

In this study, the performance of eco-friendly concrete produced by utilizing waste marble as a total aggregate replacement was evaluated. The experimental findings indicated that the developed waste marble aggregate concrete (WMC) specimens successfully met the standardized strength requirements for structural applications. The main objective of this investigation was to determine the experimental and statistical correlation between destructive strength tests and the non-destructive ultrasonic pulse velocity (UPV) test, taking into account the content ratios of concrete. This study presents an experimental and statistical investigation to correlate destructive strength properties with non-destructive UPV measurements in eco-friendly concrete. A total of 300 concrete cubic specimens were produced by fully substituting conventional aggregates with waste marble aggregates across five distinct water-to-cement ratios (W/C = 0.20 to 0.40) and ten aggregate-to-cement ratios (WMA/C = 1.1 to 2.0). Compressive strength (f_c), splitting tensile strength (f_t), and UPV tests were conducted on the 28th day. The experimental results showed that f_c ranged from 19.2 to 37.5 MPa, f_t from 2.3 to 4.4 MPa, and UPV from 3580 to 4386 m/s, confirming the high structural quality of the waste marble aggregate concrete. Non-linear regression analyses were performed using IBM SPSS Statistics 22 to develop empirical models predicting destructive strengths based on mix design parameters and UPV data. The proposed statistical models demonstrated high accuracy with determination coefficients (R²) of 0.98 for f_c and 0.97 for f_t, backed by low mean absolute relative deviations (6% and 8%, respectively). The findings indicate that the developed empirical formulations can reliably evaluate the strength of WMC in a practical and non-destructive manner. Full article

This study evaluates the mechanical and durability performance of mortar incorporating paint sludge ash (PSA) as a partial replacement for ordinary Portland cement (OPC), with emphasis on predictive modeling and multi-response optimization using response surface regression techniques. PSA was produced through controlled calcination of industrial paint sludge and characterized by a high content of pozzolanic oxides (SiO₂ + Al₂O₃ + Fe₂O₃ > 70%), indicating pozzolanic potential. Its contribution to mortar performance is attributed to filler effects and pozzolanic reactions. Experimental dataset covering PSA contents (0–20%) and curing age (3–91 days) using Design-Expert software to evaluate their combined effects on compressive strength, ultrasonic pulse velocity (UPV), bulk density, water absorption, porosity, and sulfate resistance. The developed models demonstrated good predictive capability, with coefficients of determination (R²) ranging from 0.9073 to 0.9777, although significant lack-of-fit was observed for some responses, suggesting localized deviations that were not fully captured by the global polynomial models. Model adequacy was supported by ANOVA results, close agreement between adjusted and predicted R² values, low coefficients of variation (<10%), high adequate precision values (>4), and satisfactory residual diagnostic analyses. Results indicate that curing age enhances the measured performance parameters due to continued hydration and pozzolanic reactions, while PSA content exhibits a nonlinear effect governed by competing mechanisms. At moderate replacement levels (≈10–11%), through densified matrix and pore refinement, higher replacement levels reduce performance due to dilution of cementitious phases and slower reaction kinetics. Desirability-based multi-response optimization predicted an optimum PSA replacement level of approximately 10.57%, corresponding to a predicted compressive strength of 39.78 MPa at 91 days with prediction errors below 5%. Durability indicators were also improved within this range. Overall, PSA is demonstrated to be a viable supplementary cementitious material for sustainable mortar production. Full article

This study investigates the thermo-mechanical and microstructural performance of concrete incorporating waste tire rubber (WR) and recycled steel fibers (WS) under elevated temperatures. Four mixtures were prepared: plain concrete (PL), rubber-modified concrete (WR5), and hybrid mixtures containing 0.4% and 0.8% steel fibers (WS0.4WR5 and WS0.8WR5). Specimens were exposed to temperatures of 400 °C, 600 °C, and 800 °C to simulate fire conditions. The results indicate that the incorporation of rubber reduces compressive strength at ambient temperature due to its lower stiffness and weak interfacial bonding. However, the addition of recycled steel fibers significantly improves crack resistance and enhances thermal stability. At 400 °C, the WS0.8WR5 mixture showed a retention rate of 92.9% (absolute strength: 44.32 MPa), compared to 72.2% for plain concrete (absolute strength: 44.11 MPa). Although the hybrid mixture has a lower ambient strength (47.68 MPa vs. 61.07 MPa), its superior retention makes it competitive in fire scenarios. Ultrasonic pulse velocity (UPV) measurements revealed a strong correlation with compressive strength degradation, confirming its effectiveness as a non-destructive indicator of internal damage. Microstructural analyses (SEM, XRD, and TGA-DTA) demonstrated that elevated temperatures lead to dehydration, phase transformation, and increased porosity, while steel fibers help maintain matrix integrity through crack-bridging mechanisms. The findings highlight a synergistic interaction between waste rubber and steel fibers, offering a sustainable and effective approach for improving the fire resistance of concrete. Full article

Nowadays, for energy-based targets, investigations on the thermal characteristics of building materials are becoming increasingly common. Foam concrete is one of them. Foam concrete, which is already a very popular building material in terms of thermal insulation, needs to simultaneously improve its mechanical and thermal characteristics. Therefore, in the present study, we address the effects on foam mortars of blended cements containing zeolites. The replacement ratios of blended cements containing two different zeolites were 0, 10, 30, and 50%. This study aims to encourage the use of alternative additives to achieve objectives such as sustainability, energy efficiency and lower carbon emissions and to obtain optimum design data for the foam concrete market. The parameters examined in 28-day-old samples were basic physical characteristics, water absorption, ultrasonic pulse velocity (UPV), compressive strength, thermal characteristics and microstructure analysis. Based on the test results, for foam mortars containing blended cement with analcime and clinoptilolite, a 10% replacement ratio is optimal in terms of strength, whereas a 30% ratio is required for a significant improvement in thermal insulation. The foam mortars with a 10% analcime replacement ratio demonstrated the highest specific heat capacity. Full article

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

This study evaluates the feasibility of utilizing wood ash (WA), derived from grilled-fish barbecue waste, as a supplementary cementitious material, in combination with crushed clay blocks (CCB) as partial or full replacements for natural coarse aggregate, to improve the sustainability of concrete. A total of twelve concrete mixtures were produced using WA replacement levels of 0%, 10%, 20%, and 30% and CCB replacement levels of 0%, 50%, and 100%. The concrete specimens were evaluated in terms of workability, compressive strength, splitting tensile strength, flexural strength, density, water absorption, ultrasonic pulse velocity (UPV), thermal conductivity, and microstructural characteristics using scanning electron microscopy (SEM). The results show that replacing cement with 10% WA achieved the highest mechanical performance at 56 days, with compressive, splitting tensile, and flexural strengths of 50.58 MPa, 5.54 MPa, and 6.07 MPa, respectively. These results represent an improvement of 11% in concrete properties compared with the control mixture. However, the use of 20% of WA enhanced microstructural densification through pozzolanic reactions, whereas higher replacement levels resulted in increased porosity, the presence of unreacted particles, and reductions in strength and UPV values. In contrast, increasing the WA and CCB contents reduced density and workability while significantly increasing water absorption. Among the investigated mixtures, the combination of 10% WA and 50% CCB provided the most favorable balance between mechanical performance, thermal efficiency, and sustainability. Further studies are recommended to evaluate the long-term durability and economic feasibility of the proposed replacement levels for sustainable concrete production. Full article

This study investigates the use of mussel shells (MSs), a biogenic by-product of the food industry, as a partial replacement for ground granulated blast furnace slag (GBFS) in alkali-activated mortars. Given their high CaCO₃ content, MSs represent a sustainable secondary raw material that reduces both waste disposal burden and reliance on natural resources, while offering a low-carbon alternative to conventional cement-based binders. Alkali-activated mussel shell/slag mortars (AAMSs) were produced with MS replacement ratios of 0%, 5%, 10%, 15%, and 20% by mass of GBFS. Sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) were used as alkaline activators. Fresh specimens were cured at 60 °C for 48 h. The experimental program included workability, compressive and flexural strength, water absorption, porosity, density, capillarity, ultrasonic pulse velocity (UPV), and freeze–thaw (F-T) resistance tests. Increasing MS content slightly reduced flowability and mechanical strength, while increasing water absorption, porosity, and capillarity. The M0 series achieved the highest 28-day compressive strength (54.06 MPa), while M15 exhibited the highest flexural strength (5.23 MPa). Following F-T cycling, the 5% and 10% MS series demonstrated the best compressive strength (30 MPa). The 10% MS exhibits a relatively balanced overall performance, providing the best balance between mechanical performance, F-T resistance, and microstructural stability, as confirmed by scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDS) analyses showing elevated Ca/Si ratios and the formation of Ca-rich crystalline phases. Full article

Prismatic mortar specimens with dimensions of 40 × 40 × 160 mm were produced in accordance with TS EN 196-1:2016 using rice husk ash (RHA) as a partial cement replacement at levels ranging from 0% to 15%. The specimens were exposed to aggressive seawater and 7% NaCl environments and evaluated through compressive strength, flexural strength, ultrasonic pulse velocity (UPV), water absorption, carbonation, capillary water absorption, and thermal conductivity tests. The highest compressive strength values were generally obtained at RHA replacement levels of 8–10%, depending on the exposure condition and curing period. In the 7% NaCl environment, most RHA-incorporated mixtures exhibited higher flexural strength than the control mixture, with the highest values generally observed at replacement levels between 6% and 10%. UPV results indicated that the incorporation of RHA did not significantly impair the internal quality of the mortars. Water absorption, capillary water absorption, and carbonation depth generally increased with increasing RHA content, particularly at replacement levels of 10–15%. No carbonation depth was observed in the control specimens, whereas the highest carbonation depths were measured in the 15% RHA mixtures. Thermal conductivity decreased with increasing RHA content, with the lowest values obtained at the highest replacement levels. Overall, the results indicate that RHA replacement levels of approximately 8–10% provide a favorable balance between mechanical performance, durability-related properties, and thermal insulation performance under aggressive chloride-rich exposure conditions. Full article

The construction industry contributes significantly to global CO₂ emissions, primarily due to the production of ordinary Portland cement (OPC). As a sustainable alternative, geopolymer concrete, utilizing industrial by-products, such as ground granulated blast furnace slag (GGBFS) and fly ash (FA), has attracted increasing attention. However, studies on the post-fire behavior of high-strength slag–fly ash-based geopolymer concrete (HSSFGC) remain limited. In this study, two HSSFGC mixtures with FA contents of 10% and 30% were prepared and exposed to elevated temperatures of 100 °C, 300 °C, 450 °C, and 600 °C. After natural cooling, mass loss, ultrasonic pulse velocity (UPV), residual compressive strength, and microstructural evolution were investigated using XRD, FTIR, TGA, SEM, and EDS techniques. The results show that as temperature increases, mass loss and internal defects also increase, accompanied by deterioration of the interfacial transition zone (ITZ). At 100–300 °C, specimens with higher FA content exhibited improved residual compressive strength due to secondary geopolymerization of unreacted FA. However, above 300 °C, all specimens experienced significant strength degradation, with residual compressive strength at 600 °C reduced to 57% for FA-10 and 49% for FA-30 of their respective room-temperature values. This mix-specific difference, attributed to higher pore connectivity and more severe dehydroxylation in FA-30. These findings reveal the temperature-dependent degradation mechanisms of HSSFGC and provide a theoretical basis for post-fire assessment and sustainable engineering applications. Full article

In this study, the effect of substituting waste glass aggregate and recycled concrete aggregate (RCA) at different ratios (20%, 40%, 60%, 80%, 100%) on the compressive strength performance of geopolymer concretes reinforced with tire-derived textile fibers (TDTF) was investigated. A total of 22 different mixtures were prepared, and their 7-day and 28-day compressive strengths, water absorption rates, and ultrasonic pulse velocity (UPV) were determined. The results showed that TDTF improved compressive strength in both waste aggregate series, with a more pronounced contribution at 28 days. Increasing the waste glass aggregate content reduced 28-day compressive strength by 16–31% compared with the control mixture, whereas RCA mixtures showed only 1–4% strength loss up to 60% replacement and 17–19% loss at higher replacement levels. Glass aggregate mixtures generally exhibited higher early-age strength, while RCA mixtures performed better at 28 days. TDTF addition increased the 28-day compressive strength by approximately 25–30%, depending on aggregate type and replacement level. The lowest water absorption value was obtained in the fiber-reinforced glass aggregate series, whereas the highest value was measured in the RCA series, mainly due to the porous adhered mortar on RCA particles. Based on the compressive strength, water absorption, and UPV results, RCA replacement levels up to 60% and glass aggregate replacement levels of 40–60% may be considered suitable for the mixtures examined in this study. Full article

Testing harvested logs is a critical step in the wood products supply chain. Non-destructive evaluation (NDE) methods are essential for grading and sorting logs, especially given variations associated with tree age. In this study, plantation-grown Eucalyptus nitens from two age groups were sourced from two Tasmanian harvesting sites for NDE and comparison with destructive stiffness testing. The key finding is that the correlation between dynamic modulus of elasticity (DMOE) and static modulus of elasticity (MOE) weakens with increasing age, particularly at the whole-log level. For further analysis, the radial location of recovered small clear samples (from pith to bark) was examined. Core samples (near the pith) showed the strongest correlation between DMOE and static MOE (R² = 0.51), followed by middle (R² = 0.46) and outer samples (R² = 0.25). This study demonstrates that considering the radial location of recovered samples is a more effective approach for improving grading accuracy. Age is a key factor for initial segregation of logs before applying NDE for property analysis of both logs and recovered samples. Full article

Cement is widely used worldwide but contributes to environmental issues due to its reliance on non-renewable resources and high CO₂ emissions. Incorporating waste materials, such as eggshell ash (ESA) and granite waste powder (GWP), as partial cement replacements offers a sustainable approach to reducing the environmental impact of mortar production. This study investigated the effects of replacing cement with a blended eggshell ash–granite waste powder (ESAGWP) mixture at 0%, 5%, 10%, 15%, 20%, 25%, and 30% by weight. Experimental tests evaluated fresh, hardened, and microstructural properties, including workability, compressive strength, bulk density, water absorption, porosity, ultrasonic pulse velocity (UPV), and resistance to sulfate attack at curing ages of 3, 7, 28, 56, and 91 days. The results showed that a 15% replacement of cement with ESAGWP provided optimal performance, maximizing compressive strength, bulk density, and UPV, particularly at later curing ages. At this optimal level, compressive strength reached 35.00 MPa, 36.77 MPa, and 37.58 MPa at 28, 56, and 91 days, respectively, representing improvements of approximately 28.0%, 28.8%, and 26.6% over the plain cement control mix at the corresponding ages. Replacements beyond 15% led to reduced strength, increased porosity, and higher water absorption due to unreacted particles. Microstructural analysis revealed that the ESAGWP15 mix achieved a dense and well-packed matrix, correlating with improved mechanical and durability properties. Overall, the study demonstrates that ESAGWP can serve as an effective supplementary cementitious material (SCM), with 15% replacement recommended for balanced performance and sustainability in mortar production. Full article