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This study examines the strength development of fly ash-based geopolymer (FAG) as a stabilizer for road base material for pavement construction. In the last decade, there has been a rapid development of conventionally treated bases, such as cement-treated bases. However, a major problem with this kind of application is the shrinkage cracking in cement-treated bases that may result in the reflection cracks on the asphalt pavement surface. This study explores the effects of FAG on base layer properties using mechanistic laboratory evaluation and its practicability in pavement base layers. The investigated properties are flexural strength (FS), unconfined compressive strength (UCS), shrinkage, and resilient modulus (RM), as well as indirect tensile strength (ITS). The findings showed that the mechanical properties of the mixture enhanced when FAG was added to 80–85% of crushed aggregate, with the UCS being shown to be a crucial quality parameter. The effectiveness of FAG base material can have an impact on the flexible pavements’ overall performance since the base course stiffness directly depends on the base material properties. As a stabilizing agent for flexible pavement applications, the FAG-stabilized base appeared promising, predicated on test outcomes.

Despite the current advancements in, and increasing use of renewable types of energy, approximately 40% of the world’s electricity is still produced by coal fired power stations. This trend is significantly higher in some continents, for example approximately 70% in India and up to 90% in South Africa. In this study the fly-bottom ash (FBA) mixture with different component percentages of BA (bottom ash)100, FA (fly ash) 25-BA75, FA50-BA50, FA75-BA25 and FA100 were modified with 2% of poly-vinyl alcohol (PVA), and tested in terms of particle size distribution, specific gravity, pH, surface morphology, mineralogical-compound content, and engineering properties. The physiochemical modified FBA were examined via scanning electron microscope (SEM), X-ray fluorescence, and Fourier transform infrared spectroscopy (FTIR) analysis. Polymeric-modified FBA for all compositions exhibited high pH values within the range of 10.11–10.70. SEM image exhibited agglomerated and strongly bonded PVA-modified FBA with FA50-BA50 composition because of the effect of polymer that reacted with the fine ashes. The unsubstantial shift in peak position of Si/Al-O stretches showed electrostatic interaction between PVA and FBA based on FTIR analysis. The PVA-modified FBA at composition of FA50-BA50 increased the gradient of stress–strain curves, which significantly improved the strength behavior of PVA-modified FBA sample. It is thus imperative that other sustainable methods of managing coal combustion-by products be expanded .

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