Ductility and strength of reinforced concrete beams intrinsically reinforced with polypropylene fibres

One of the horizons through which a more cost effective concrete can be conceived and be able to satisfy constructional requirements as well as modern society's demand, would be the Green Concrete concept. It has been for decades that sustainable design is drawn into direct attention of different sectors of society. From the structural point of view, the invaluable goal of this project is to improve the ductility of the concrete structural element which helps eliminate or reduce the need for steel reinforcement in concrete structures. Trend of improvement in human knowledge is promising and so far this project, like other projects with the same aim, is contributing to inevitable changes in the construction industry. Cracking in reinforced concrete causes stiffness reduction which is the reason for decreasing the capacity of the structure in bearing structural loadings. Concrete is a brittle material and its failure is mostly due to this characteristic. Different methods have been used to overcome this problem and give ductility to concrete matrix. Using short fibres like steel fibres or synthetic fibres and polymeric material is of attention to improve this behaviour of concrete. The effect of these additives is more on the post peak behaviour of concrete which improves the strain softening where tension is applied. Fibres within the matrix, can bridge the cracks which improves the performance of concrete matrix and results in a better stress bearing material. Different types and percentages of polypropylene fibres have been investigated for the mechanical properties of concrete. From among these mixes two best are selected and reinforced beams are casted to be tested under four point bending test. Results show that by using high percentage of PP fibre in the reinforced concrete beam, ductility can be improved by 160 %.