Coal ash is obtained in the combustion of coal for electricity production in coal based power stations. The non-combustible by-product including bottom ash and fly ash are discarded as a landfill. Consequently, the hazardous elements contained in the ashes can adulterate the ground and surface water. This study was carried out to emphasize the engineering properties of bottom ash collected at Tanjung Bin power station. An experimental study was carried out for particle size analysis, specific gravity, shear strength, compaction and relative density. The results depict that bottom ash possess particle size distribution nearly identical to sand, low specific gravity and dry density as compared to natural soil and having higher internal friction angle closer to granular materials. Based on the results, bottom ash can be employed in roadways, embankments and filling material for retaining walls by virtue of its low specific gravity, easy to compact and good frictional characteristics.

The construction of embankment over soft clay is quite a challenging job for the geotechnical engineer, which may results in a large settlement, bearing failure and stability issues. Stone columns can be used to minimize the settlement and increase the bearing capacity in such conditions. This study was carried out to investigate the behaviour of bottom ash columns underneath embankments using numerical modelling. The soft soil improved with bottom ash columns under the embankment subjected to traffic-induced loading was simulated in Plaxis 3D foundation software. The study variables include three area replacement ratios (Ar) of 10%, 15% and 20% and two columns length of 5m and 7.5m. The results indicated that enlarging the Ar and length of columns significantly reduced the final settlement and consolidation time. The maximum settlement reduction of 58% was reported for the Ar of 20% with 7.5m column depth. The study suggests that bottom ash columns can be used to improve soft soil underneath the embankment.

Coal ash is generated as a raw product during combustion in thermal power plants. These industrial wastes include fly ash and bottom ash, which has been deemed as a source materials for geopolymer. Bottom ash is used in soil columns for stabilizing foundation soil. In the present study bottom ash from Tanjung bin power station was used as a substitute materials for making geopolymers. The effect of alkali activator to bottom ash ratio on the undrained shear strength of bottom ash based geopolymer was studied. The molarity of sodium silicate solution was kept as 14, Na2SiO3/NaOH of ratio 2.5, mass ratio of alkali activator to bottom ash 0.40, 0.50 and 0.60, and steam curing at 65°C were attempted for the samples. The experimental results of UU triaxial test indicate that alkali-activator to bottom ash ratio of 0.50 gives higher undrained shear strength.