Experimental investigation of quaternary blended sustainable concrete along with mix design optimization

The application of pozzolanic materials used either singly or in conjunction with other materials in concrete not only improves the mechanical and durability properties but can provide eco-environmental benefits, as well. This study is an effort to make concrete more sustainable by partially substituting cement with industrial and agricultural waste materials such as fly ash (FA), pumice (Pu) and rice husk ash (RHA) to understand their combined effects on fresh properties, mechanical properties, and sorption of quaternary blended concrete samplings. For this resolve, fifteen different mix proportions of quaternary blends were prepared for evaluating the above-mentioned properties. The maximum values of standard consistency, initial setting time and final setting time were observed to be 38.5%, 162 min and 261 min for C50-F10-R15-P25, C70-F15-R5-P10 and C50-F10-R15-P25, respectively. The compressive and flexural strength of all specimens improved with time. Some specimens showed significant compressive strength and flexural strength gain (about 43% and 57% more than the 28 days values at 120 days, respectively). Similarly, the quaternary blended specimens demonstrated excellent durability, as evident from the lower water intrusion values of the sorption test. The optimized values of mix design constituents as obtained from the response surface methodology approach revealed that a maximum compressive strength of about 44.44 MPa can be obtained if the sand-to-cement ratio (s/c), water-to-cement ratio (w/c) and curing age are 2.5, 0.5 and 90 days, respectively and keeping the amount of FA, RHA and Pu as 50 kg/m³, each.