The Expermental Study Of The Mechanical Properties And The Freezing-Thawing Damage Of The Layer Hybrid Fiber Reinforced Concrete

The layer hybrid fiber reinforced concrete is a new concrete that the fiber of high elastic modulus is bestrewed in the upper and lower surface of a certain thickness, and the polypropylene fiber is distributed in the whole concrete members uniformly. This concrete occurs hybrid effect through doping two types of fiber in form on the one hand , and utilizes the stress characteristics of the pavement concrete in structure on the other hand. The study about the new concrete that intermixes the carbon fiber and the polypropylene fiber is not multiple. This paper analyzes the mechanical properties briefly according to LHFRC, and discusses its freezing-thawing damage primarily on this basis, so as to provide reference for the application of pavement engineering in the future. Main works as following:The first, it studies the effects of the main factors, such as water-binder ratio, the content of fly ash, the content of the polypropylene fiber and the content of the carbon fiber on the 28d mechanical properties of the layer hybrid carbon fiber-polypropylene fiber reinforced concrete by using the second-degree current spinning combination design of four factors. The result shows that, quadratic polynomial regression model can be used to establish the regression equation of the 28d compressive strength and flexural strength of the layer carbon fiber and polypropylene fiber. When the water-binder ratio is 0.3, the content of fly ash,the content of the polypropylene fiber and the carbon fiber are all 0, the 28d compressive strength of the layer carbon fiber and polypropylene fiber can reach the maximum 68.21 MPa; While the four factors respectively are 0.3,0%,1.2% and 1.6%,the maximum 28d flexural strength is 8.84 MPa. The effect of polypropylene fiber and the layer carbon fiber on the concrete compressive strength is little, but significant on the concrete flexural strength;The second, with the rapid frozen thaw method, this paper comparative studies the frost resistance of the ordinary concrete(OC),layer carbon fiber reinforced concrete (LCFRC),polypropylene fiber reinforced concrete(PFRC) and layer hybrid fiber reinforced concrete(LHFRC) after 100 times freeze-thaw cycles. The study shows that, the frost resistance of the LHFRC is the best, and its loss of flexural strength post freezing is least;The third, this paper studies the damage evolutional law of the above four types of concrete, determines the concrete parameters, regresses the damage evolutional equation. The results show that the model of damage evolution is suitable for that four types of concrete of our test conditions, and it can characterize their freezing-thawing damage evolution process better.