Search Results (54)

The incorporation of supplementary cementitious materials derived from agro-industrial residues has emerged as a promising strategy to reduce the environmental impact associated with Portland cement production while promoting circular economy principles. This study investigates the influence of palm oil fuel ash (POFA) as a partial cement replacement on the mechanical and microstructural properties of concrete. Concrete mixtures containing 0%, 10%, 15%, and 20% POFA by mass of cement were produced using a constant water-to-binder ratio of 0.47. Compressive strength was evaluated at 7, 14, 28, and 56 days, while microstructural characterization was performed using scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM–EDS) to assess hydration products and the interfacial transition zone (ITZ). The incorporation of POFA resulted in lower compressive strength at early curing ages, with reductions of approximately 16–21% compared with the control mixture, reflecting the slower kinetics of pozzolanic reactions. However, prolonged curing promoted significant strength development. At 56 days, concretes containing 10% and 15% POFA exhibited compressive strengths 3.7% and 9.2% higher, respectively, than the control concrete, whereas the 20% replacement level resulted in a 14.6% reduction. SEM observations revealed a denser cementitious matrix, improved aggregate–paste bonding, and a more refined ITZ in mixtures containing 10–15% POFA. EDS analysis showed Ca/Si ratios of 1.22 and 1.08 for the 10% and 15% POFA mixtures, respectively, indicating the formation of silica-rich C–S–H gel associated with effective pozzolanic activity. The results demonstrate that POFA can be successfully utilized as a supplementary cementitious material in concrete. While the 15% replacement level produced the highest 56-day compressive strength, both the 10% and 15% mixtures exhibited favorable microstructural characteristics and effective pozzolanic activity, indicating that both replacement levels are suitable for sustainable concrete production. Full article

Agricultural waste materials can serve as functional constituents in cement-based composites through three pathways: (i) organic bio-aggregates that lower density and alter thermal behavior, (ii) lignocellulosic fibers that control cracking and improve post-cracking resistance, and (iii) agro-ash supplementary cementitious materials (SCMs) that densify pore structure and reduce permeability when ash quality and curing are controlled. This review draws on 98 papers, with coconut shell aggregate and coir/coconut fibers as the core focus; agro-ash SCMs (notably palm oil fuel ash, POFA, and rice husk ash, RHA) enter where they clarify mechanisms or inform hybrid design. Rather than cataloging compressive-strength data, the synthesis is organized around controllable process inputs (feedstock conditioning, mix design, curing) and the interface-governed mechanisms that determine performance: interfacial transition zone (ITZ) character and pore connectivity. In coconut shell systems, density reductions come at a cost: elastic modulus drops and moisture sensitivity rises unless shell conditioning, particle packing, and matrix refinement are managed. In fiber systems, gains in toughness and residual capacity are bounded by mixing workability and by the long-term stability of the fiber–matrix bond under alkaline and wet–dry exposure. A mix must first meet strength, serviceability, and transport requirements before its embodied impact is compared with conventional alternatives. The contribution is to reframe these systems around controllable processing and interface mechanisms instead of tabulated strength values; preparation, treatment, and characterization data are consolidated into bounded design windows, an explicit core versus supporting evidence convention is applied, and sustainability is judged under functional equivalency rather than per-volume carbon. Full article

This research investigates the relationship between mineralogical composition and compressive strength in alkali-activated cement–sand mortars incorporating palm oil fuel ash (POFA) as a partial replacement of Portland cement. POFA was introduced at 5 wt.% and 10 wt.% of the binder, and activation was achieved using a NaOH–Na₂SiO₃ solution (3:1 mass ratio). Compressive strength and bulk density were evaluated at 7 and 28 days, while phase evolution was analyzed by X-ray diffraction (XRD) coupled with Rietveld refinement. The results demonstrate that POFA incorporation significantly modified the CaO–SiO₂–Al₂O₃ balance of the system, promoting the consumption of portlandite and the formation of Na- and K-rich aluminosilicate phases such as albite and muscovite. The control mixture exhibited the highest compressive strength values, whereas increasing POFA content reduced both strength and density due to calcium dilution, lower gel compactness, and increased porosity. Nevertheless, all mixtures exhibited progressive strength development over time, indicating continued hydration and geopolymerization reactions associated with the formation of hybrid C–(N,K)–A–S–H gels. These findings demonstrate that POFA can effectively participate in alkali-activated hybrid binders when applied at controlled replacement levels, highlighting its potential as a sustainable supplementary material for lower-carbon cementitious systems. Full article

Palm oil waste (POW) is generated during the production of palm oil, and a large quantity of this waste often travels to landfills for disposal. This review aims to provide a comprehensive understanding of the circular economy approach to sustainable engineering and environmental applications of POW, including its generation, disposal concerns, challenges, and prospects. This review provides an overview of the features, composition, and prospective applications of several POWs, including palm oil clinkers (POCs), palm oil fuel ashes (POFAs), palm oil kernel shells (POKSs), and palm oil fibres (POFs). Furthermore, this overview describes the different applications that POW has found, such as sustainable construction materials, renewable energy production, and environmental remediation. Moreover, this review discusses the leaching and risk assessment of POW. The overview also discusses the circular economy implications of using POW. The results showed that while some wastes are reused and recycled, a good quantity are still discarded in environmentally harmful ways. With this overview of a wide circular economy approach to the sustainable use of POW, there will be a rallying call to experts and researchers to identify research gaps that could contribute to the sustainable use of POW. The results of this overview of the sustainable engineering and environmental applications of POW with a circular economy approach indicate that cleaner production technologies and better environmental sustainability of the palm oil industry are feasible through proper waste management, renewable energy generation, resulting in minimal environmental impacts. Furthermore, this analysis will be very useful in providing tools to engineers, environmentalists, and other relevant stakeholders to enable the efficient and sustainable use of POW in the global circular economy. Full article

Geopolymers are a new breed of construction materials that are environmentally friendly and replace old Portland cement. These materials are produced through the alkaline activation of industrial and agricultural waste rich in aluminosilicates. The growing interest in sustainable building solutions has driven research into their development. Palm oil fuel ash (POFA) and waste ceramic tile powder (WTCP) are both highly rich in reactive aluminosilicates and widely recommended for the production of sustainable geopolymers. This study aims to evaluate the suitability of POFA and WTCP as sustainable alternatives to conventional binders and to identify the potential advantages of each waste material in developing eco-friendly, high-performance geopolymers. The results indicate that specimens prepared with a high content (50 wt%) of POFA or WTCP, incorporating fly ash and slag, can achieve compressive strengths of up to 50 MPa after 28 days of curing. However, increasing the proportion of POFA or WTCP from 50% to 60% and 70% resulted in a significant reduction in compressive strength. In contrast, specimens containing higher proportions of POFA and WTCP demonstrated superior durability when exposed to aggressive environments. In summary, the findings indicate that WTCP is more suitable than POFA for producing geopolymers as eco-friendly construction materials. Its superior reactivity, workability, early-age strength development, and durability make it a promising precursor for sustainable applications in the construction sector. Full article

The rapid growth of the palm oil industry produces large amounts of palm oil mill effluent (POME), which contains high organic content and is challenging to treat using conventional ponding systems. These traditional systems often fail to meet discharge standards for biochemical oxygen demand (BOD) and chemical oxygen demand (COD). This study tested anaerobic biofilm reactors enhanced with biochips and chemically treated palm oil fuel ash (TPOFA) to improve POME degradation and biogas production. Two 3 L reactors were operated at the same feed-to-microorganism (F/M) ratio: a control (C) and a combination of both (P + B). Biochips helped microbes attach and form biofilms, while TPOFA acted as an adsorbent, creating better conditions for anaerobic breakdown. The P + B reactor outperformed others, achieving over 95% COD removal, high microbial biomass (MLVSS: 24,500 mg/L), and the highest biogas yield at 917 mL per day. Microbial analysis showed dominant groups, including phyla groups of Halobacterota, Bacteroidota, and Firmicutes. Class Methanosarcina in archaeal phylum of Halobaterota was key in converting acetate to methane. Bacteroidota primarily aided organic matter breakdown and nutrient removal, while Firmicutes supported hydrolysis and electron transfer. Less abundant Desulfobacterota also helped by interacting with methanogenic archaea. Overall, combining biochips with TPOFA in anaerobic biofilm reactors offers an effective, sustainable method for treating POME and recovering renewable energy through biogas. Full article

Geopolymers have emerged as promising materials for their superior thermal and mechanical properties, offering sustainable alternatives to conventional coatings. This study investigates the potential of Palm Oil Fuel Ash (POFA) as a raw material for fire-resistant geopolymer coatings. Through the optimization of POFA-to-alkaline activator (AA) ratios, NaOH concentrations, and curing temperatures, POFA-based coatings were synthesized and applied to mild steel substrates. Fire resistance testing revealed that the optimal formulation (0.35 POFA ratio, 8 M NaOH concentration, and curing at 65 °C) achieved a temperature at equilibrium (TAE) of 151.2 °C, significantly outperforming other compositions by reducing heat transfer during fire exposure. Thermal imaging and SEM analysis demonstrated that the optimized coating (GP-POFA8) exhibited a more uniform and stable intumescent layer, leading to lower peak temperatures (909 °C) compared to less optimized samples. Thermogravimetric Analysis (TGA) further confirmed that GP-POFA8 retained approximately 80% of its original mass at temperatures beyond 600 °C, highlighting its superior thermal stability. These findings underscore the potential of POFA-based geopolymers as effective, eco-friendly solutions for fire-resistant applications in construction and industrial sectors, contributing to sustainable waste management. Full article

This article presents the results of a systematic review investigating the potential of agricultural wastes as sustainable and low-carbon alternatives in reinforced concrete (RC) production. Background: The depletion of natural resources and the environmental burden of conventional construction materials necessitate innovative solutions to reduce the carbon footprint of construction. Agricultural wastes, including coconut shells (CSs), rice husk ash (RHA), and palm oil (PO) fuel ash, emerge as promising materials due to their abundance and mechanical benefits. Objective: This review evaluates the potential of agricultural wastes to improve sustainability and enhance the mechanical properties of RC structural elements while reducing carbon emissions. Design: Studies were systematically analyzed to explore the sources, classification, and material properties of agro-wastes (AWs), with a particular focus on their environmental benefits and performance in concrete. Results: Key findings demonstrate that AWs enhance compressive strength, tensile strength, and modulus of elasticity while reducing the carbon footprint of construction. However, challenges such as variability in material properties, limited long-term durability data, and lack of standardized guidelines hinder their broader adoption. Conclusions: AWs hold significant potential as sustainable additives for RC elements, aligning with global sustainability goals. Future research should address material optimization, lifecycle assessments, and regulatory integration to facilitate their mainstream adoption in construction. Full article

Biodiesel, an eco-friendly alternative to conventional fossil fuels, offers reduced emissions like carbon dioxide, sulfur oxides, and soot. This study explores biodiesel production from a blend of waste oils using a novel biomass-based catalyst derived from the bottom ash of a biomass boiler. Catalyst synthesis involved wet impregnation, a unique approach using previously unreported bottom ash. Characterization via SEM-EDS, BET, FTIR, and XRD revealed its composition and structure. Optimization of biodiesel production involved assessing alcohol molar ratio, catalyst concentration, and reaction time, achieving a maximum FAME concentration of 95% under specific conditions. Blending residual palm oil with waste frying oil enhanced biodiesel properties, demonstrating a maximum FAME concentration at specific catalyst concentration (8%), molar ratio (1:10), and reaction time (2 h). Catalyst reusability, up to three cycles without significant yield variation, showcased its sustainability. The catalyst, primarily composed of calcium, a characteristic biomass bottom ash component, exhibited mesoporous features. Impregnation with eggshells not only altered composition but also ensured a uniform particle size distribution. FTIR and XRD analyses indicated calcium in hydroxide and crystallized forms. Effective catalyst separation methods included decanting or water washing, with optimal biodiesel purity achieved through 3% phosphoric acid washing at 60 °C. Various recovery methods were assessed, highlighting hexane washing as the most efficient, enabling up to three catalyst reuse cycles without substantial efficiency loss. Full article

Geopolymer mortars made from various waste products can appreciably reduce carbon dioxide emissions and landfill-related issues, making them viable substitutes for ordinary Portland cement, a workhorse in the concrete industry. Thus, a series of ternary geopolymer mortars were made and characterized to determine the effects of exposure to elevated temperatures (from room temperature up to 900 °C) on their engineered (residual compressive strength, weight loss, and slant shear bond strength) and microstructural properties. These mortars, which contain fly ash, ground blast furnace slag, and a high volume of palm oil fuel ash, were designed to activate via the incorporation of an alkali activator solution at a low concentration (molarity of 4). The elevated temperature-mediated deterioration of the ternary geopolymer mortar was quantified using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The results revealed an improvement in the ternary geopolymer mortars’ resistance against elevated temperatures when the palm oil fuel ash level in the mortar matrix was raised from 50 to 70% and when slag was replaced by fly ash. It was asserted that the proposed ternary geopolymer mortars may contribute to the advancement of green concretes demanded by the construction sectors. Full article

Alkali-activated binders have become popular in the construction industry for their eco-friendly attributes. Various wastes from industries and agricultural sectors containing high concentrations of aluminosilicate and calcium oxides can be used to design these binders. This study evaluated the effect of high-volume granulated blast furnace slag, fly ash, and palm oil fuel ash additions on the bond strength performance of the proposed geopolymer mortars. Various levels of slag (50, 60, and 70%) and fly ash were substituted by palm oil fuel ash to determine the impact of SiO₂:Al₂O₃, CaO:SiO₂, and CaO:Al₂O₃ and their proportions on the geopolymerization process and the strength performance of the designed mortars. The bond strength performance of the mortars was assessed in terms of slant shear, flexural, and splitting tensile strength tests. The mineral properties of the designed mortars were obtained using X-ray diffraction, scanning electron microscopy, and Fourier transform infrared measurements. The incorporation of fly ash and palm oil fuel ash in the mortars caused a considerable decrease in the CaO:SiO₂ and CaO:Al₂O₃ ratios, thus reducing the geopolymerization process and strength performance. The reduction in slag from 70% to 50% was counterbalanced by the increasing content of fly ash and palm oil fuel ash, which led to a drop in the compressive strength from 97 MPa to 56 MPa. In each level of slag, the replacement of fly ash by up to 10% palm oil fuel ash added more loss in strength values. In addition, the surface morphology of prepared mortars with lower palm oil fuel ash content was significantly enhanced, indicating the presence of less porosity and unreacted particles. The achieved mortars were asserted to be extremely well matched with the concrete substrates, offering effective binders for widespread construction uses. Full article

Researchers have investigated the feasibility of using ultrafine palm oil fuel ash (u-POFA) as a cement replacement material because of its potential to reduce the environmental impact of concrete production. u-POFA, a by-product of palm oil fuel combustion, is a suitable replacement for Portland cement in concrete mixes because of its sustainability and cost-effectiveness. This study investigated the microstructural and compressive strengths of alkali-activated mortars (AAMs) based on fly ash (FA) and granulated blast-furnace slag (GBFS) being added with varying percentages of u-POFA. The mixture samples were prepared in eighteen mortars using sodium metasilicate (Na₂SiO₃) as the source material and sodium hydroxide (NaOH) as the alkaline activator. This study used field-emission scanning electron microscopy coupled with energy-dispersive X-ray spectrometry, X-ray diffraction, X-ray fluorescence, and Fourier-transform infrared spectroscopy to characterize the binary-blended mortars after 28 days of curing and determined the strength of the FA+GBFS (87.80 MPa), u-POFA+GBFS (88.87 MPa), and u-POFA+FA mortars (54.82 MPa). The mortars’ compressive strength was influenced by the CaO/SiO₂ and SiO₂/Al₂O₃ ratios in the mixture, which was directly due to the formation rate of geopolymer products of the calcium–alumina–silicate–hydrate (C–(A)–S–H), aluminosilicate (N–A–S–H), and calcium–silicate–hydrate (C–S–H) phases. Based on the contents of FA and GBFS, u-POFA significantly enhanced concrete strength; therefore, u-POFA used in a suitable proportion could enhance binary-blended AAMs’ microstructure. Full article

Supplementary cementitious materials (SCMs) are strongly advised as an alternative to cement to reduce its adverse environmental effects. One such SCMs is palm oil fuel ash (POFA), a waste material generated in large quantities in Southeast Asian countries, and there is insufficient data on its use in engineered cementitious composite (ECC). This study aims to optimize the properties of ECC using POFA as a cement replacement, by using 13 mixes developed by response surface methodology (RSM) with the POFA (at 20, 30, and 40% cement replacement levels) and PVA fiber (at 1, 1.5, and 2% volume fractions) as the input factors. The compressive, tensile, and flexural strengths, and tensile capacity (CS, TS, FS, and TC) were assessed. The microstructural properties were determined using Field-Emission Scanning Electron Microscopy (FESEM) and Mercury Intrusion Porosimetry (MIP). Results indicated that while the ductility and strain capacity increased with POFA, the strengths decreased by up to 51.5%. However, a structural POFA-ECC could be made with up to 30% POFA and 1–5% PVA fiber. The RSM optimization revealed 27.68% POFA and 2% PVA fiber as the optimal levels of the input factors, with the experimental validation correlating with the predicted values at less than 10% error. Full article