Development of Bottom Ash as Pozzolanic Material

Abstract

This research studies the potential of using bottom ash from the Mae Moh power plant in Thailand as a pozzolanic material. Bottom ash, which was rarely used in concrete due to its inactive pozzolanic reaction, improved its quality by grinding until the particle size retained on Sieve 325 was less than 5% by weight. Bottom ashes before and after being ground were investigated and compared for their physical and chemical properties. The bottom ashes were used to replace portland cement type I in mortar and concrete mixtures. The results indicated that the particle of bottom ash was large, porous, and irregular shapes. The grinding process reduced the particle size as well as porosity of the bottom ash. Compressive strengths of mortar containing 20–30% of bottom ash as cement replacement were much less than that of cement mortar at all ages, but the use of ground bottom ash produced higher compressive strength than the cement mortar after 60 days. When ground bottom ash was used at a 20% replacement of cement to make concrete, the concrete with higher cement content produced higher percentage compressive strength as well as a higher development rate than those of the low cement content concretes. With the cement content in ground bottom ash concrete of 440 and 260 kg/m³, the concrete needed 14 and 60 days, respectively, to develop higher compressive strength than that of the concrete without bottom ash. As a result of the compressive strengths, it was concluded that ground bottom ash could be used as a good pozzolanic material.