The expansive behaviors of the expensive concrete under different restraining conditions were systemically studied. The experimental results indicate that expansive deformation obviously increases before 10 days and tends to be constant after 25 days regardless of the restraining conditions. The mixture ratio of expansive cement and restraining conditions are the main factors affecting expansive deformation. Self-stress can be obtained when the expansive deformation is restrained. The higher self-stress could be obtained when the expensive concrete is restrained by steel tube. For specimens under steel tube restraining, the wall thickness and the length of the steel tube have important influence on self-stress. Both the radial self-stress and axial self-stress in concrete core increase when wall thickness or length of the steel tube increases.
Combining with the technology of self-compacting concrete,self-stressing concrete and con-crete-filled steel tube,we can get self-compacting and self-stressing concrete-filled steel tube.In order to study the expansive mechanism of self-stressing concrete,the continuous observation of 47 days on six specimens was carried on.The specimens have different steel area to concrete area ratio.The expansive process in hoop and axial direction were studied,and the expansive mechanism was discussed too.The experimental results identify that the creep and elastic deformation take a large proportion in effective free expansion.The calculating formu-las of self-stress in hoop and axial directions were presented here.
