The effect of polymer materials on the fracture characteristics of high performance concrete (HPC)

Compared with most construction materials, concrete is considered as a brittle material, and its brittleness increases with the compressive strength. For super-high-strength concrete, failure can be sudden, explosive and disastrous. Also the tensile strength is not proportionally increased. Therefore, it is necessary to carry out research on the brittleness of concrete in order to establish parameters for assessing the brittleness, find ways to improve the brittleness and tensile strength, and eventually design and manufacture concrete materials with high strength and low brittleness. In this study, strengthening and toughening effects of polymer materials on the high performance concrete (HPC) were investigated. The HPC was manufactured using ordinary Class 52.5 N Portland cement, silica fume and superplasticizer. The adopted polymers included the styrene-butadiene-rubber (SBR) latex, polyvinylidene chloride (PVDC), linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) with contents of 1.5%, 3% and 5% in weight of cement content. The measured material and fracture properties included compressive and tensile strengths, modulus of rupture, Young’s modulus, fracture energy, fracture toughness and brittleness. The test results at 28 days indicate that the addition of 1.5% and 3% SBR, PVDC, LLDPE and HDPE into the HPC could largely improve the compressive strength by up to 15.7%, while the addition of 5% SBR, LLDPE and HDPE did not show any enhancement except for 5% PVDC which increased the compressive strength by 10.9%. The tensile strength was considerably increased for all dosages of polymers, with the maximum increases of 72.7% and 83.2% for 3% SBR and 1.5% LLDPE, respectively. The fracture energy were also enhanced by adding 1.5% SBR and all dosages of LLDPE, with a maximum increase of 24.3%, while there were no indications of enhancement for other dosages of polymers. The modulus of rupture, fracture toughness and Young’s modulus were not improved for lower dosages of polymers but slightly decreased for higher dosages. The brittleness decreased monotonically with increasing amount of LLDPE, but it increased with increasing amounts of SBR, PVDC and HDPE