Research On Expansive Performance Of Expansive Agent In Steel Tube Concrete

The shrinkage of core concrete in steel tube concrete is one of the reasons that cause the disengaging between concrete and steel tube. For preventing the disengaging between concrete and steel tube, this paper research the effect of only mixing and double admixture agent on the shrinkage of core concrete.The expensive performance of only mixing and double admixture expensive agent under closed condition has been studied. The results indicated that both only mixing and double admixture can't exert full expensive performance, but possess some shrinkage-compensating properties, and the shrinkage-compensating properties of double admixture is more notability than the shrinkage-compensating properties of only mixing. When ZY:MgO=1:1,the shrinkage-compensating properties is most notability.The expensive performance of expensive agent under closed,standard and water condition has been studied. The results indicated that water scarcity under closed condition is the main reason causing the expensive agent can't exert full performance The expensive performance of expensive agent after increasing W/B ratio under closed condition has been studied. The result indicated that both only mixing and double admixture can exert expensive performance, but the expensive performance of only mixing ZY is more notability than double admixture. when the amount of ZY is 12%,the expensive performance is most notability.For further demonstrating that water scarcity under closed condition is the main reason causing the expensive agent can't exert full performance The specimens of closed and water condition have been studied by XRD and SEM. The results indicated that the amount and the distribution of expensive agent hydrates is different under different condition.For demonstrating the expensive performance is different with different ratio of double admixture.The specimens of three ratio double admixture have been studied by MIP.The results indicated that when ZY:MgO=1:1,the proportion of harmful pore of 100nm～1000nm is the lowest.