Untreated rice husk ash incorporated high strength self-compacting concrete: Properties and environmental impact assessments

The suitability of untreated rice husk ash (URHA) as a supplementary to the ordinary Portland cement (OPC) and fine aggregates (FA) in high strength self-compacting concrete (SCC) was investigated in terms of mechanical properties as well as environmental impact assessments (EIA). In total, nine SCC mixes were prepared and investigated with various levels of URHA replacements to OPC and FA. Initially, the fresh and hardened properties of URHA incorporated SCC were determined. Further, EIAs were carried out considering eighteen different environmental impact indices for the optimum URHA incorporated SCC mixes to determine the most appropriate mix in terms of mechanical properties along with their environmental impacts. The experimental results reveal, URHA in the range of 10–15% can be used without compromising the fresh and hardened properties of SCC. The results of the EIAs are presented and discussed in terms of compressive strength to environmental indices ratios to normalise the comparison. The EIAs disclose that even through some of the mixes provide better performance in terms of certain environmental impact categories; especially CO2 emission, water pollution (fresh and marine) and ecotoxicity, their strength to environmental impact ratios are relatively low. Thus, it is recommended to select the optimum mix design of URHA incorporated high strength SCC in terms of mechanical properties and as well as EIA