Experimental Study on Vacuum-Assisted Pumping Technique of Steel Tube-Confined Concrete

A new technique for construction of steel tube-confined concrete (STCC), i.e., vacuum-assisted pumping technique was put forward in this paper, and the simulation research both in laboratory and on the building site had been done. The test results showed that the formation of air membrane between steel tube and core concrete could be effectively inhibited by controlling the air content of concrete through optimizing design for mix proportion of concrete and by regulating the vacuum pressure in steel tube during the process of concrete pumping, and thus the density of concrete was increased and the bond between steel tube and concrete was improved. Therefore, the performance of STCC structure such as the ultimate load-bearing capacity was enhanced. Moreover, this new technique can decrease the difficulty of concrete pumping. The technology had been applied in the construction of Yichang Yangtze River Bridge in Yichang-Wanxian railway.