Capping Systems for High-Strength Concrete

This study focused on the effects of capping systems on the compressive strength of high-strength concrete (HSC). The three systems investigated were ground ends, bonded caps, and unbonded pads. Five compressive strength groups were examined with strength levels ranging from 6,000 psi to 14,000 psi. The capping compounds investigated were commercially available and advertised for testing HSC. The unbonded pads were neoprene pads with a Shore A Durometer hardness of 70. A grinding machine was used to obtain the required planeness and perpendicularity on the ground end cylinders. No significant difference was found between the capping systems at the 6,000-psi, 10,000-psi, and 14,000-psi levels. Significant differences were detected at the 8,000-psi and 12,000-psi levels. In the 8,000-psi group, ground ends produced significantly lower compressive strengths than three of the capping compounds. For the 12,000-psi group, ground ends produced significantly lower strengths than one of the capping compounds and the unbonded pads. In all strength levels but the 6,000-psi level, the ground ends method produced lower average compressive strengths than the other methods studied. These results imply the viability of alternative methods of end treatments such as unbonded pads and capping compounds for use with HSC.