Malaysia is one of the largest palm oil producers in the world and its palm oil industry is predicted to generate a large amount of waste, which increases the need to modify it for sustainable reuse. The green geopolymers produced from industrial waste can be a potential substitute for cementitious binders. This type of polymer helps reduce dependency on cement, a material that causes environmental problems due to its high carbon emissions. Palm oil fuel ash (POFA) geopolymer has been widely investigated for its use as a sustainable construction material. However, there is still uncertainty regarding the total replacement of cement with POFA geopolymer as a binder. In this study, we examined the effects of different material design parameters on the performance of a POFA-based geopolymer as a building material product through iterations of mixture optimisation. The material assessed was a single raw precursor material (POFA) activated by an alkaline activator (a combination of sodium hydroxide and sodium silicate with constant concentration) and homogenised. We conducted a physical property test, compressive strength test, and chemical composition and microstructural analyses to evaluate the performance of the alkali-activated POFA geopolymer at 7 and 28 days. According to the results, the optimum parameters for the production of alkali-activated POFA paste binder are 0.6 liquid-to-solid ratio and 2.5 alkaline activator ratio. Our results show that the use of alkali-activated POFA geopolymer is technically feasible, offering a sustainable and environmentally friendly alternative for POFA disposal.

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The global consumption of aggregate in the construction field is increasing annually, especially in concrete production. With the development of the economy and increase of the population, the demand for concrete and, therefore, a huge amount of aggregate has increased significantly. This issue is pressing and needs to be addressed. Lightweight aggregate (LWA) is one possible solution. This study investigated the potential use of artificial LWA manufactured from alkaline-activated palm oil fuel ash (POFA) with silt due to its properties and performances. Six mixes containing up to 60% silt by total weight combined with optimised activated POFA were analysed. The artificial LWA was synthesised through a pelletising and sintering process at 1150 °C. The increase in the activated POFA proportion in the mixture induced changes in the properties of artificial LWA, including the physical and mechanical properties, durability, and microstructure. The analytical results showed that all of the artificial aggregates were categorised as LWA, based on BS EN 13055. The artificial LWA with 40% activated POFA and 60% silt had the highest crushing strength and acceptable properties for construction applications. This study summarised the performances of the final products and highlighted the different uses of imported silt and POFA as building materials for minimising environmental impacts.

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