A study of the workability and compressive strength characteristics of corn cob ash blended cement concrete

The study investigated the workability and compressive strength characteristics of corn cob ash (CCA) blended cement concrete. Nine classes of CCA-blended cements were employed with the CCA content ranging from 0% to 25%. The 0% CCA replacement involved the use of normal ordinary Portland cement and it served as the control. The mix proportions of cement:sand:granite used were 1:1½:3, 1:2:4 and 1:3:6 with 0.5, 0.6 and 0.7 water-to-cement ratios, respectively. The concrete cubes were tested at the curing ages of 3, 7, 28, 60, 120, and 180 days. Slump and compacting factor tests were carried out to check the effect of CCA on the workability of concrete. The results showed that the concrete slump and compacting factor decreased as the CCA content increased indicating that concrete becomes less workable (stiff) as the CCA percentage increases. The compressive strength of CCA-blended cement concrete was lower than the control at early ages, but improves significantly, and outperforms the control at later ages (120 days and above). The optimum compressive strength of 57.10 N/mm2, 40.30 N/mm2 and 28.07 N/mm2 for 1:11/2:3, 1:2:4 and 1:3:6 mix proportions, respectively at 180 days were obtained at 8% CCA replacement level. It was concluded that only up to 8% CCA substitution is adequate where the blended cement is to be used for structural concrete.