Strength characteristics of marine clay mixed with coal ash and cement with microstructural verification

This study uses coal ash obtained from the Tanjung Bin coal power plant consisting of a mixture of fly ash and bottom ash at different ratios. Such mixtures will be used with the minimum amount of Ordinary Portland Cement to stabilise marine clay. Compaction data corresponding to a mixture of coal ash and OPC mixed with marine clay soil provides 1535 and 1600 kg/m3 MDD and 18–22.2% OMC ranges, as additive percentages are increased. The unconfined compressive strength test indicated the highest increase at 50BA:50FA ratio with a value of 536 kPa at 15% of additive. The strength of the treated soil sample would also increase with increasing additive percentage and curing period. The XRD of untreated soil sample indicates composition intensity for minerals like quartz, mica, kaolinite, calcite, montmorillonite, and muscovite generally decreased with curing time; on the other hand, halloysite composition reduced. However, a new mineral is formed: calcium aluminium silicate hydroxide hydrate. Moreover, the FESEM results show that the treated marine clay surface particles looked denser with time. Structural voids were also reduced. In line with the XRD and FESEM test outcomes, the EDX results indicated that the formed cementitious products comprised calcium aluminate silicate hydrate.