Experimental Study On Micro-expansion Concrete

To be easily cracked is the inherent fault of concrete. And expansive concrete is the most effective way to resolve the cracking problem. Expansive concrete is a kind of special concrete which is made of expansive cement or adding fixed amount of expansive agent for concrete when making common concrete.Basing on a comprehensive analysis of the current research situation in China and abroad, main problems, the types of expansive agent and the corresponding expansive mechanism of micro-expansive concrete, this paper explores the experimental research on expansive agent's influence to concrete's performance. Experiment embarked on the research for workability, compressive strength, flexural strength, impermeability and free-expansion ratio for micro-expansive concrete. The results of the research show that:(1) With the increasing of UEA expansive agent in volume; the initial slump of concrete mixing decreases. With the increasing of HEA expansive agent in volume, the initial slump of concrete mixing gradually increases.(2) The compressive, flexural strength of concrete of different ratios increases with the growth of age. When expansion volume is 14%, the concrete is not fit for the designing requirements. The compressive strength of the concrete mixed with expansive agent is lower than that of the blank concrete specimen. The compressive, flexural strength of concrete of the same age concrete decrease with the increasing of the expansive agent. Under the standard curing condition, the compressive, flexural property of the concrete is superior to that under the packaged cling. The compressive, flexural properties of the concrete mixed with UEA expansive agent is superior to the concrete mixed with HEA expansive agent.(3)The impermeability of concrete of different mixing ratios increases with the increasing of expansive agent volume. Under the standard curing condition, the impermeability of concrete is superior to that under the packaging condition. The impermeability of the concrete mixed with HEA expansive agent is superior to the concrete of mixed with UEA expansive agent.(4) Under the standard curing condition, free-expansion ratio concrete of different mixing ratios slowly grows before the concrete age of fourteen days with the growth of ages. After the age of fourteen days, free-expansion ratio decreases. Peer concrete swelling increases with the expansion of the free content; free-expansion ratio of concrete mixed with expansive agent is higher than free-expansion ratio of the blank concrete specimens. Wrapped in cling film, before the three days age, free-expansion ratio of concrete of all kinds of mixing ration increases with the increasing of expansive agent; after the three days age, the free-expansion ratio of concrete of all kinds of mixing ratio decreases with the increasing of expansive agent. The free-expansion ratio of concrete under standard curing condition is higher than under condition of being wrapped in cling film; the free swelling of concrete mixed with HEA expansive agent is higher than concrete mixed with UEA expansive agent.