Utilisation of coal bottom ash in zero carbon footprint pavement-quality geopolymer concrete

Worldwide demand for natural fine aggregate (NFA) in the construction sector has skyrocketed in recent decades, and supplies of NFA are becoming more scarce. At the same time, thermal power plants produce massive quantities of coal bottom ash (CBA), which has adverse environmental impacts. However, studies have shown that CBA can be used as a replacement for NFA in concrete preparation. In this study, the fresh and mechanical properties, durability characteristics and fatigue life of pavement-quality geopolymer concrete (PQGPC) mixes prepared with the partial addition of CBA as partial NFA replacement were investigated. After 28 days of curing, the compressive and flexural strengths of a PQGPC mix with the use of 30% CBA (GPC-30) were in accordance with the requirements for rigid pavements. Furthermore, compared with the regular PQGPC mix, GPC-30 had a 2% lower endurance limit against fatigue at two million cycles at different stress levels (0.55, 0.60, 0.65 and 0.70). Even though GPC-30 was found to have 19% lower flexural strength than the regular PQGPC, the fatigue life was comparable. The use of CBA to prepare ‘green’ PQGPC pavements not only lessens the reliance on NFA but also reduced the need for landfill.