Impact Resistance of Concrete with Partial Replacements of Sand and Cement by Waste Rubber

Effects of partial replacements of sand by waste crumb rubber and fine rubber, and cement by powder rubber, on the performance of concrete under low velocity impact loading were investigated. Specimens were prepared for 5%, 10% and 20% replacements by volume for both sand and cement. For each case, six beams of 100mm x 100mm x 500mm were subjected to 5.15 kg hammer from 900mm height. The number of blows of the hammer required to induce the first visible crack and ultimate failure of the beam were recorded. The results are presented in terms of impact energy required for the first crack and ultimate failure. The crumb and fine crumb rubbers increased the impact energy for both first crack and ultimate failure; the increase of impact resistance by crumb rubber was more than that by fine crumb rubber. However, the impact energy for both first crack and ultimate failure increased by the replacement of sand with fine crumb and crumb rubbers until 20%, while this energy increased with cement replacement by powder rubber until 10% replacements and then decreased, but is still higher than that of plain concrete.