Utilisation of Recycled Silt from Water Treatment and Palm Oil Fuel Ash as Geopolymer Artificial Lightweight Aggregate

Abstract

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.