Effect of Hyper-plasticizer Additive Rates on the Properties of Polypropylene Fibre Tempered Concretes

In this study, effect of different rates of hyper-plasticizer additives on the physical and mechanical properties of polypropylene fibre tempered concretes was investigated. The factors of slump and compaction, which are fresh concrete properties, were also examined. In the study, different types and rates of polypropylene fibres were used. Polypropylene fibres and hyper-plasticizer additives were used in three different rates in the mixture. As polypropylene fibre amount increased in the mixture, hyper-plasticizer additive amount also increased. Fresh concrete slump values were measured between 15 and 19 cm. Impaction factor value was between 0.89 and 0.99. In some mixtures, it was seen that the relation between the slump value and impaction value was disrupted. Abrasion and water absorption values, which were physical properties of the hardened concrete, were calculated. In abrasion tests, it was seen that concretes with C, D and E fibres were eroded less. Polypropylene fibre additive increased the water absorption value of concrete. Its effect on splitting-tensile strength, which was a hardened concrete property, was examined. In splitting-tensile strength experiment, 15 × 30 cm cylinder samples were used. It was seen that the polypropylene fibres increased the splitting-tensile resistance of the concrete at the rate of 80% compared to the polypropylene fibre additive free mixture. Also, deformation meters were placed on the sample in splitting-tensile resistance. Horizontal deformations of samples were measured at the moment of breaking. While horizontal deformation values increased in 7 day samples compared to propylene fibre additive-free mixture, they decreased in 28-day samples. 7 day horizontal deformation values of the samples were measured to be higher than the 28 day horizontal deformation values. This situation can be explained with brittleness of the concrete at the end of 28 days as it gains resistance.