Experimental Study On The Properties Of High Performance Concrete With Polypropylene Fiber After High Temperature

As the broad bridge, the tunnel and the high building's popularity, the high performance concrete with the characters of high intensity, good endurance and excellent utility is on application day by day . However, comparing with the common concrete, the strict construction, the greater crisp character and the lower penetrability,lower firefighting properties. Especially, when facing the high temperature, it is very easy to spalling. In resent years, the fire is occurring very frequently, and it is also one of the main causes of destroying the building's construction. Research the firefighting character of the high performance concrete in a systemic way is a hot topic in civil engineering, in which though the way that adding the polypropylene fiber to improve the firefighting character is an important direction in present study. So the study about the character of the high performance concrete with polypropylene fiber after the high temperature is a topic which has both the academic and realistic sense.This paper will take the Wuhan Tunnel project as an example, take the improving the fire-resisting character of the tunnel lining structure as the purpose. Though the high temperature testing of the pipe material's high performance concrete of the Wuhan Tunnel project, heating the high performance concrete (which are not added the fiber concrete test coupon and added the polypropylene fiber test coupon) to different temperature, and then taking the test of mechanical properties after the high temperature, We use the ultrasonic non-destruct testing technology to analyze the lose of the concrete which is heated by high temperature and to find the best parameter of the polypropylene fiber. This paper has achieved those below:(1).The test shows that as the temperature is becoming more and more higher, the color of the concrete turns from light to deep, and the destroy of the exterior is become more and more serious. We get the conclusion that the physic characters of the changing-rule about the concrete after high temperature (in color and exterior destroy). The temperature of the fire can be estimated from these physics character, which will provide guide for the testing, identify and the evaluation about the fire in future. (2.)Though testing the concrete test coupon's compression resistant and the splitting tensile strength after the high temperature, we get the mechanics changing-rule of the concrete after high temperature and also get the information about the intensity loss. On basis of the given match proportion and the way to rise, to constant and to cool the temperature of the high performance concrete in this paper, we will use the test data to analyze the relationship among the compressive strength, the splitting tensile strength and the high temperature.(3.)In our test, the concrete coupons which not add the polypropylene fiber exploded in 400℃, but not the added one. The spalling-resistant character is obviously. This shows that the polypropylene fiber is good for the spalling resistant, and also probe into the theory why this fiber could improve the high performance concrete's character in this way. Though the test, we have an overall research about the effects of the polypropylene fiber to the high performance concrete's mechanics character after high temperature and analyze different fiber parameter's effects to the improving of the high performance concrete's firefighting character. After the comparison of remains' intensity in different temperature, we found that the concrete with 1.5kg/m3 polypropylene fiber parameter's loss is relatively the least.(4.)Though the ultrasonic non-destruct testing of the concrete coupon after high temperature, the ultrasonic speed become lower as the temperature's increase. We found that the changing-rule among the compressive strength, the tensile strength and the velocity of sound of the concrete remains after high temperature. We established the relation equation between the temperature in fire of the concrete structure and the speed of the ultrasonic, the strength of the concrete after fire and the velocity of sound in the regression analysisThough the research and analyze of the mechanics character of the high performance concrete with different polypropylene fiber after fire and the ultrasound test, we get some conclusions which are helpful for the future study about the high temperature characters of the high performance concrete.