Application Of Hybrid Fibers Reinforced Self-Compacting Concrete In The Precast Noise Barrier

With the development of urban construction, the noise pollution near the railway became more and more seriously. Now, different kinds of noise barriers are studied and applied in order to resolve the pollution near the speedway and railway. The precast concrete noise barrier is one of the extensive ways. The sectional area of sound absorption in the precast concrete noise barrier is very small, so it's very easy to cracking while the concrete subjects to plastic and dry shrinkage. The used noise barriers must receive the shake and attack of the air current, which increase the possibility of cracking. In order to erase the crack near the sound absorption, the concrete used to precast noise barrier must have good crack resistance and mechanical property.At present, fiber reinforced concrete (FRC) and self-compacting concrete (SCC) are widely used. FRC can reduce the structural and non-structural cracks effectively. Fibers transfer stress by the interface bonding with concrete, avoiding stress concentration, achieving stress redistribution, so as to reduce the cracks of concrete and increase the toughness of concrete. SCC is an innovative concrete that does not require vibration for placing and compaction. It is able to flow under its own weight, completely filling formwork and achieving full compaction, even in the presence of congested reinforcement. The hardened concrete is dense, homogeneous and has the same engineering properties and durability as traditional vibrated concrete.In order to apply fiber (high alkali-resistant glass fiber (GF), modified polypropylene fiber (PPF) and hybrid fibers) reinforced self-compacting concrete (FRSCC) to the noise barrier, some experimental investigations were performed. Such as the workability of the fresh FRSCC test, free shrinkage test, restrained shrinkage test, splitting performance test and flexural performance test.Result of tests show that all the FRSCC workability receives the standard of EFNARC. The speed rate of free shrinkage is quick in early age (1 day) and all fibers have a little positive effort on it. Crack resistance of SCC can be improved by single type of GF or PPF. They can reduce the area, the length and the width of the crack. Glass-PP hybrid fibers can improve the crack resistance of SCC much better than mono fiber. Both GF and PPF have positive influence on the splitting and flexural strength of SCC. The splitting strength flexural strength, splitting toughness and flexural toughness can be improved by the contents and length of the PPF. The hybrid fibers reinforced SCC is better than that of mono fiber on the splitting strength, flexural strength, splitting toughness and flexural toughness.On the basis of experimental investigations and comparative analysis, one of the best hybrid fibers reinforced self-compacting concrete has been found, which has good workability, high crack resistance and good mechanical performance. Using this material to produce noise berrier, cracks in the sound absorption have almost disappeared.