Influence of Particle Size of Bottom Ash on Mechanical Properties of M30 Grade Concrete

Abstract

Thermal power plants produce fly ash and bottom ash as by-products. A total of 70% of by-product from thermal power plants accounts for fly ash and remaining 30% is bottom ash. One of the most common uses of bottom ash at the present scenario is structural fill in its coarser form only, and it is reported that the disposal leads to leaching of heavy metals to the groundwater table. These disposal problems and potential health hazards can be reduced by large usage of bottom ash in construction industry. A larger percentage of usage of the bottom ash in concrete will significantly reduce the potential health hazards and will give solution to disposal problems. With this in view, bottom ash collected from the Udupi thermal power plant was classified into two different levels according to their particle size and replaced against fine aggregates for different replacement levels, in producing M30 grade concrete. The raw bottom ash was coarse and classified as Zone-I after sieve analysis. The classification of bottom ash according to the particle size was carried out into different zones such as Zone-II and Zone-III, according to the specifications from IS 383–1970. The attainment of required compressive strength is directly correlated to particle size of bottom ash. Results show 47% reduction in compressive strength of concrete when raw bottom ash was (Zone-I) was replaced by 50% in place of natural river sand (NRS). A little effort in grading the bottom ash and converting coarser raw bottom ash from Zone-I to finer Zone-II bottom ash has proved beneficial in improving the compressive strength of concrete. It was observed that lower specific gravity of bottom ash directly influences density of concrete, which intern has adverse effect on compressive strength. The bottom graded as Zone-II can be replaced to NRS by 15–20%, with little compromise in compressive strength. Through value addition of 5% extra cement content, there is a possibility to increase the replacement level of Zone-II bottom ash to 30% with similar compressive strength as that of control concrete. Through cost analysis, it was found that 30% replacement of Zone-II bottom ash in place of NRS with 5% extra cement content as value addition was found to be economical. © 2021, Springer Nature Singapore Pte Ltd.