By adding an appropriate amount of expansive agent into the core concrete of concrete filled steel tube(CFST),the shrinkage of concrete can be compensated,and the mechanical properties of CFST structures or components also can be improved.Deformation performances of micro-expansive lightweight aggregate concrete filled steel tube under two different conditions are tested,including free deformation and limited deformation,by changing the amount of expansive agent of specimens.The results show that under the free deformation condition,the greater the amount of expansive agent,the slower the tendency of shrinkage of concrete at each stage.As for expansion-limited properties,the development trends of strain-time curves of each group are similar.Namely,the hoop strain of the outer wall of the steel tubes increases at first,and then it decreases,finally it tends to be stable.The maximum tensile strain of the steel tube wall in the curing period is smaller with the increase of the volume of the expansion agent.The shrinkage of concrete filled steel tube can be compensated well when the amount of expansive agent is 12％.%在钢管核心混凝土中掺加适量膨胀剂,可补偿混凝土的收缩,改善钢管混凝土结构或构件的力学性能.配制不同膨胀剂掺量微膨胀轻骨料混凝土,分别制作了棱柱体试件和钢管混凝土试件,测试其在自由膨胀及限制膨胀两种条件下的变形性能.试验结果表明:在自由膨胀状态下,膨胀剂掺量越大,各阶段混凝土收缩的趋势越缓慢;在钢管限制膨胀状态下,各组试件的应变-时间曲线发展趋势大致相同,钢管外壁的环向应变均先增大后减小,直至最后趋于稳定,膨胀剂掺量越大,养护前期管壁的最大拉应变越小.膨胀剂掺量为12％时可较好地实现钢管混凝土的补偿收缩.
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