Preparation And Basic Performance Studies Of Hybrid Copper Covering Steel-PVA Fiber-reinforced Reactive Powder Concrete

As a delegate of high-performance concrete, reactive powder concrete（RPC）hasbeen born for nearly30years, yet as a result of its high cost, and the rigorous requestof materials, its application in China is limited. Therefore, for the purpose of reducingits cost and optimizing its performance, RPC may be better and broad used instructures, the method of preparing it and its basic performance are investigatedthrough two ways, improving the performance of matrix and using fibers to reinforceit.Firstly, on this basis of the developments of theories of fiber-reinforced concrete,the current situation of RPC(reactive powder concrete), as well as the hybridfiber-reinforced concrete being introduced in this paper, the effects of followingfactors to the strength of RPC are investigated as follows. The ratio of sand andcement, different proportions of sodium sulfate, curing temperature, as well as theaddition of silica fume, fly ash, and grounded furnace slag. The results show that, thebest ratio of sand and cement is1.1:1. Better grain gradation would cause higherstrength. The highest acceptable dosage of sodium sulfate is1%, otherwise the matrixmay be swelled. The fume ash is beneficial to the water retention, and addingappropriate proportions of fly ash and grounded furnace slag can not reduce thestrength of RPC but can improve the workability. According to experiments, a highcompressive strength of181MPa can be gained. Secondly, the reinforcing effects of adding single kind of fiber (copper coveringsteel and PVA) and hybrid fibers are studied through experiments. Thefiber-reinforcement mechanisms, destroyed pattern of fiber-matrix, and the positiveinteractions of two kinds of fiber are investigated too. On the balance of mobility,strength, and economical factors, the optimal mixing ratios are selected as follows.PVA with the length of6mm and copper covering steel fiber shall be chose as1%and1.5%by volume respectively. When it comes to PVA with the length of12mm andcopper covering steel fiber, the volume fraction of PVA should not exceed1%, and theoptimal volume fraction of copper covering steel fiber is1%.Finally, four types of concrete, RPC without fibers, PVA fiber-reinforced RPC,copper covering steel fiber-reinforced RPC and PVA&copper covering steel fiber-reinforced-RPC are compared by splitting tensile test. The results indicate that, RPCmatrix is high in compression strength but low in tensile strength, after beingreinforced by fibers, the toughness of it can be enhanced. PVA fiber is better inincreasing the compression strength than tensile strength, and copper covering steelfiber can increase the toughness of matrix remarkably. Moreover, the hybrid fiberreinforcement is better than single kind of fiber, and the proportion depends on needs.