Performances of concrete containing coal bottom ash with different fineness as a supplementary cementitious material exposed to seawater

Abstract

Concrete structures are seriously deteriorated under marine environment because marine water is aggressive in nature; it contains salts of sulphate and chloride and others. These salts deteriorate the plain and reinforced concrete structures. However, most of previous research was investigated on concrete performances exposed to single solution, such as sulphate or chloride attack, even though the actual conditions are the combination of both. Therefore, the object of this study is to evaluate the performances of concrete containing coal bottom ash (CBA) with different fineness as a supplementary cementitious material (SCM) exposed to seawater. This study considered 10% ground CBA as a SCM in concrete. The original CBA was ground in a ball mill for 20 and 30 h, to get different particle fineness. Initially all specimens were cured in normal water for 28 days as to achieve targeted strength and then half of the specimens were shifted into seawater for further 28, 56, 90 and 180 days and other specimens were kept in normal water. The particle fineness of CBA influence on the concrete performances was assessed in terms weight variations, compressive strength and chloride permeability. Experimental results demonstrated that concrete strength with CBA of fineness 3836 cm2/g (type-A) delivers around 11.9% and 8.5% higher than control mix in water and seawater respectively at 180 days. Subsequently, concrete strength with CBA fineness of 3895 cm2/g (type-B) brings about 12.7% and 5.8% greater than control mix in water and seawater respectively at 180 days. However, it was also detected that concrete with CBA-type-A and CBA-type-B exhibits around 45.4% and 42.4% reduction in chloride penetration as compared to control mix at 180 days. Hence, it was concluded the strength performances of CBA-type-B is superior than the control mix at 28 days. However, CBA-type-A gives the better performances at later ages of 90 and 180 days. Hence, CBA-type-A is suggested for the future studies, based on strength performances and resistance to chloride penetration. This study encourages the use of ground CBA in concrete as SCM in normal as well as in marine environment. Keywords: Coal bottom ash, Particle fineness, Supplementary cementitious materials, Seawater, Compressive strength, Chloride permeability