ENCAPSULATION OF GROUND BOTTOM ASH AS SUPPLEMENTARY CEMENTITIOUS MATERIALS FOR CEMENT MORTAR

Abstract

Excessive carbon dioxide (CO2) emissions due to the Portland cement manufacturing process have encouraged the industry to look for more sustainable alternatives to cement. Supplementary cementitious material (SCM) has been widely used to improve concrete performance through considerable research. By-product waste, such as fly ash, has been utilized in many construction projects. It is an effective solution to solve long-term environmental pollution. As one of the coal industry by-products, bottom ash has similar chemical properties compared to fly ash, but it is rarely used as SCM because of its size. Therefore, this research aims to modify the regular bottom ash and observe the strength development of cement mortar incorporating bottom ash as SCM. The pre-treatment process of bottom ash was performed by 4 hours of milling to produce micro-size particles. The chemical and physical properties of modified bottom ash were evaluated before being cast into cement mortar specimens. Various percentages of cement replacement using modified bottom ash were used in this research. The evaluations include X-ray fluorescence (XRF) analysis, specific gravity, particle size analysis, scanning electron microscope-energy dispersive X-ray (SEM-EDX), normal consistency, and setting time. The compressive strength and strength activity index were evaluated to obtain the strength development and optimum composition of cement mortar incorporating bottom ash, caused by pozzolanic activity. The results indicate that bottom ash positively affects the strength development of cement mortar, and it can be used as SCM to produce more sustainable cement-based construction materials.