The Research Of Air Entraining Agent On Concrete Rheological Properties And Bubble Characteristic Parameters Effect

With the improving requirements of concrete construction and the rapid development of electronic, concrete technology should not stay in the empirical foundation. It is very urgent to study and discuss the concrete performance from concrete rheology theory, and air-entraining concrete is the inevitable direction of development of concrete structure durability. Therefore, it has a practical and theoretical significance to research the influence of air entraining agent on mortar and concrete rheological properties and bubble characteristic parameters.The influence of four representative air entraining agent on mortar rheological properties were researched. The results showed that mortar slump was greatly increased in low flow state, while slightly reduced in high flow state by air entraining agent. With the increase of gas content, mortar plastic viscosity increased, and the low flow state mortar yield stress reduced, high flow state mortar slightly improved. While mortar yield stress significantly increased and slump loss amplified with B air entraining agent of greater molecular weight.The effect of air entraining agent on concrete workability and rheological properties was studied. The results showed that air entraining agent obviously improved concrete workability, reduced concrete exudation rate and increased plastic concrete slump, slightly reduced high flow regime concrete slump. With the increase of gas content, concrete plastic viscosity enhanced, plastic concrete yield stress slightly lessened, high flow regime concrete yield stress did not change evidently.The effect of air entraining agent on hardened concrete strength and bubble characteristic parameters was studied. It was found that air entraining agent decreased concrete compressive strength, slightly added concrete flexural strength, and folding compression ratio increased significantly. Gas content between fresh and hardened concrete had certain correlation. When gas content was less than8%, with the increase of gas content, hardened concrete bubble spacing factor and bubble average diameter reduced gradually with bubble total number increasing, it was a contrary trend as gas content was more than8%.Some methods and index were put forward to evaluate the quality of air entraining agent. Inferior air entraining agent could be judged simply through the determination of air entraining agent solution bubble capacity, defoaming time and concrete gas content loss test. The ultimate method to evaluate quality of air entraining agent should be the determination of bubble spacing factor, and it might be more accurate to evaluate the quality of air entraining agent by the ratio of bubble spacing factor and gas content of fresh concrete.