Experimental Study On Behaviour Of Macro-Polypropylene Fiber Reinforced Concrete

Synthetic fiber has different uses according to different qualities and purposes when it is mixed in concrete. Classic polypropylene fiber is a monofilament belonging to micro-fiber which can be used to reduce shrinkage cracks of concrete at early age. Mostly, it is used to prevent extension of old crack in the concrete matrix and delay the appearance of new crack. It can also enhance the deformability of concrete matrix. But it hasn't obviously contribution to improve the toughness of concrete.High performance concrete (HPC) should show various properties, such as relative high strength and workability, good toughness and excellent durability and to meet different engineering requirements. Plain concrete has high brittleness and low shock resistance, so it has difficulty in widespread availability. Steel fiber can obviously enhance cracking resistance, bending behaviour, impact resistance, fatigue resistance of concrete, the theory of steel fiber is nearly becoming mature and the application fields of steel fiber are expanding. But the price of steel fiber is high which limit its application. Polypropylene fiber reinforced concrete has merits such as low fiber content, low cost excellent resistance to chemical erosion and it has extensive application. As the development of the technique of polypropylene fiber reinforced concrete and the advance of the quality of polypropylene fiber, some scholars have attempted to mix macro-polypropylene fiber into concrete for the purpose of enhancing the toughness of concrete abroad. We also could mix steel fiber and macro-polypropylene fiber together into concrete to research the performance of steel-polypropylene hybrid fiber-reinforced concrete and use polypropylene fiber to partly replace steel fiber to reinforce concrete. There is little research on it inland presently.This article presents the experimental results of modified macro-polypropylene fiber reinforced high performance concrete such as workability, air content, compressive strength, fiexural toughness, fracture energy, the distribution of fiber on section, the failure form of the beam. The experiments have been carried out according to different international guidelines. The fiexural toughness has been deeply analyzed according to RILEM guideline. RILEM guideline has advantages in researching fiexural toughness of synthetic fiber reinforced concrete and could reflect true performance of synthetic fiber.The toughness of beams with steel fiber reinforcement and with hybrid fiber reinforcement has been compared. The energy absorption capacity and equivalent fiexural strength have beencalculated. The results show that modified macro-polypropylene fiber has better workability and energy absorption capability. We can use the modified macro-polypropylene fiber to obviously enhance the flexural toughness of concrete and can partly replace steel fiber, in order to increase the flexural toughness and reduce the cost.