Optimization of fly ash based soil stabilization using secondary admixtures for sustainable road construction

Fly ash, despite being a suitable cement substitute, is only utilized at a low rate in engineering applications, hence not contributing to its current waste mitigation efforts. Under a five-part comprehensive testing program, this study investigated the efficiency of fly ash stabilized soil when combined with secondary additives (enzymes and lime). Part one explored the suitable fly ash and enzyme dosages. Parts two and three assessed the effect of time and lime on enzymatic fly ash stabilized soil, respectively. Part four unveiled the mechanism of stabilization by secondary additives. Part five analyzed the significance and benefits of these additives in pavement stabilization. The study found that the efficiency of fly ash stabilization can be significantly improved when combined with 1% of 1:500 diluted enzyme. Addition of 2% lime has also supplemented with improved load-bearing capacity. Benefits of this research include enhanced fly ash waste mitigation, saving natural resources used as wearing course materials, and development of an alternative solution for pavement stabilization. •Improvement of fly ash stabilized soil using supplementary additives are presented.•Suitable additive dosages for fly ash-based soil stabilization are determined.•Stabilization mechanisms of additives in fly ash stabilized soil are unveiled.•Enzyme-based additives assist accelerated strength gain in fly ash stabilized soil.•Benefits of enzymatic additives in fly ash stabilized pavements are identified.