Effect of Re-vibration on the Compressive Strength of 56-aged RHA - Cement Concrete

Abstract

This paper investigates the effect of re-vibration on the compressive strength of 56 days RHAcement concrete. Eighty-four cubes (84) were cast using twelve (12) cubes each for 0%, 5%, 10%, 15%, 20%, 25% and 30% replacements of OPC with RHA respectively, to obtain the optimal value of RHApercentage replacement in the mix ratio 1:2:4 concrete mix with 0.5 water/cement ratio. The optimal compressive strength at 56 days curing was found to be 19.11N/mm2at 10% RHA. Another set of sixty six (66) concrete cubes were cast, forty two (42) of which were produced using the optimum percentage (10%) of RHA replacement while the remaining twenty four (24) cubes were produced without RHA (0%). All the cubes were re-vibrated,excluding the control cube specimen, for two (2) minutes each at an interval of ten (10) minutes after the initial vibration of mixing/placement of the concrete up to one hour duration of successive re-vibration using table vibrator and cured for 7, 28 and 56 days. These were tested for compressive strength. The results show that the maximum compressive strength (33.33 N/mm2) of revibrated 56 days(10% RHA- 90% cement) concrete was higher than 23.22N/mm2of the normal 28 days non-revibrated concrete (control 0% RHA). This result suggests that re-vibration has enhanced the compressive strength of RHAconcrete 28 days curing of the concrete and even better at 56 days curing.