Experimental Researches On The Floating Of Rubber Particles In Crumb Rubber Concrete

Crumb Rubber Concrete(CRC) is a type of new building material that is invented in America, with a history of a little more than twenty years. Its invention serves as an impetus for the development of concrete technology. And it is also a good way to handle the increasing environmental challenges from the waste rubber t ires, a good mean to protect the environment and a good method to recycle resources. C RC has a series of unique characteristics which are different from conventional concrete, namely that CRC has a higher ductility and larger deformability, better performance of anti-cracking behavior and energy-absorbing capacity and it increases the resistance to water and chloride ion penetration as well. These outstanding characteristics of CRC are responsible for the increasing heat in C RC researches in the recent years. However, C RC bears some disadvantages at the same time. Previous investigations reveal that C RC decrease s the strength of concrete, and it is not that economical as conventional concrete. In addition, it could trigger the floating phenomenon of rubber particles to the surface of the concrete which is unsuitable for the practical engineering projects.The thesis is based on experimental researches, which include compressive strength tests, density tests and distribution tests of CRC particles. Based on previous scientific findings, the author of this paper makes a series of CRC brick specimens, whose size are 100 mm×100mm×300mm and with different mixture ratios. By a cutting machine, a brick specimen can be cut into three cubic specimens or two half cut bricks. Later, we investigate the segregation of rubber particles through compressive strength tests, density tests and rubber particles distribution tests. The conclusions are made as follows:(1)The floating of rubber particles is not apparent when the slump test value of concrete is low(less than 5cm); However, if the slump value is high(higher than 14.5cm), and keep increasing, the floating effect tend to be more apparently. When the slump surpasses a certain value(near 18cm), the floating develops sharply and abruptly.(2)When the slump is high(higher than 14.5cm), the floating is more evident with an increased vibrating time within 30 seconds.(3)To a certain degree, the floating of C RC is appeased with an increased sand ratio.What's more, by establishing and solving differential equations, the paper discusses the elements which influence the segregation of rubber particles in CRC. In addition, the thesis makes a deep investigation into segregation control theories of concrete and presents some of the opinions and ways of segregation control by researchers. These discussions and analyses play an important role in controlling the floating in CRC. At the end of the paper, in order to guide practical construction projects, the author puts forward a large numbers of suggestions to control the floating in CRC.