Study On Influencing Factors Of Restrained Expansion Rate Of New Type Expansion Agent In Concrete

Concrete cracking has seriously affected the durability of concrete.The addition of expansion agents in concrete is one of the most effective solutions to the problem of concrete cracking.But many factors will affect the development of restricted expansion rate in concrete.In this paper,concrete with Mg O expansion agent and double expansion source expansion agent was studied.By comparative test,the effects of factors such as temperature,humidity,concrete strength grade,concrete cementing ma terial composition,particle size of expansive material on the restricted expansion rate of concrete with expansive agent were mainly discussed.The main conclusions are as follows:(1)Under constant temperature curing conditions.The double expansion source expansion agent showed more obvious changes than the Mg O expansive agent.Under the 20 ? curing temperature,Mg O expansion agent in the 28 days of curing age basically did not show expansion.While the restricted expansion rate of the double expansion source expansion agent showed a gradual increase with the increase of age.And expansion and strength develop coordinated.Under the 40? curing temperature,both Mg O and the double expansion source expansion agent showed a certain expansion effect.But the restricted expansion rate of the double expansion source expansion agent significantly higher than MgO expansion agent.The early strength of concrete under high temperature curing is increasing rapidly.Thus inhibiting the development of the late expansion of the specimen.Basically in the first three days of conservation that play a 90% expansion efficiency.Under the 60? curing temperature,the restricted expansion rate of the double expansion source expansion agent is unstable compared to the Mg O expansion agent.The data of restricted expansion rate appeared to fluctuate greatly.And the restricted expansion rate is less than the value at 40?.In general,In the case of elevated curing temperature,the data of restricted expansion rate appears to increase first and then decrease.(2)With the increase of curing humidity,the restricted expansion rate of expansion agent showed an increasing trend.And the double expansion source expansion agent can exhibit a certain expansion efficiency even in a low humidity environment.While the Mg O expansion agent in the dry environment showed shrinkage.(3)When the fly ash and slag powder content increased from 30% to 50%,the restricted expansion rate of the expansion agent increased first and then decreased.When the amount of fly ash and slag powder together accounted for 40% of the total amount of cementitious materials,the restricted expansion rate of the single and double expansion source expansion agents is the largest.When the dosage of fly ash and slag powder is fixed at 40%,and the ratio of the two is 3: 1,it is beneficial to the restricted expansion rate of the expansion agent in concrete.(4)By comparing the size of the expanded expansion agents' particles with the unexpanded expansion agents' particles in the concrete,it can be seen that the finer expansion agents' particles are favorable for the development of the restricted expansion rate of the expansion agent.(5)It is found that the expansion agent can improve the crack resistance of the concrete,and the crack resistance of the Mg O expansion agent is slightly better than that of the double expansion source expansion agent.