The Study On The Properties Of Crumb Rubber Concrete With U-shape Impact Test

Impact strength is one of the major indicators, which are used to evaluate the dynamic mechanical properties of metal materials. Nowadays, with the rapid and continuous development of building technology, the field of structure engineering has extended into more complicated working environments where the impact loads take place frequently, such as blast-resistant structures, the foundations in high seismic areas, the sleeper roadbed of the high-speed rail, and etc. all of these structure formations put forward higher requirements for the building materials, for example the concrete, on the properties of impact resistance. However, at present, there is no a uniform and standardized test method valuating the impact resistance of concrete in China, and thus this exploratory study is conducted.In this paper, we firstly suggest the U-shape test method of valuating the impact resistance of concrete. In our experiment, the concrete is made in a Plexiglas mold, whose shape is like the letter"U", and after a period of standard maintenance, placed on the impact test platform for the"repeated drop weight impact test". During the whole test, we keep U-shape concrete specimen fixed in the bottom steel base. And the impact resistance capacity of U-shape concrete specimen is assessed by the number of impact times the first crack appears and the specimen is completely destroyed.Moreover, based on this test method, we conduct researches on how the crumb rubber aggregate influents the impact strength of concrete in the room temperature and low temperature. In this test, we mix two groups of concrete, one of which is ordinary concrete and the other is CRC, with the same water-cement ratio. The test result shows that the crumb rubber can increase the impact resistance properties of U-shape concrete specimen, and this advantage is reflected in the first crack appearing times, the completely destroyed times, ductility index and the width of crack. Generally speaking, the crumb rubber, to some extent, can boost the ductility of concrete. Especially in the low temperature environment (-20℃), compared with ordinary concrete, whose impact resistance drop shapely, the crumb rubber can maintain the ductility of concrete much more obviously.