中文摘要：

为了研究不同膨胀剂质量分数和钢管侧限对混凝土徐变应变的影响,共进行了12组有、无钢管侧限的混凝土徐变试验。结果表明：加载龄期到480天的试验试件中,有钢管侧限的混凝土徐变应变约是无钢管侧限徐变应变的0.175~0.181倍,钢管侧限大大降低了混凝土的徐变应变。同时进行了三种不同质量分数膨胀剂（质量分数分别为4%、8%和12%）的混凝土徐变试验。结果表明：无论有、无钢管侧限的混凝土结构,膨胀剂质量分数对混凝土徐变应变的影响关系为：质量分数4%时,结构徐变应变均最大;质量分数为8%时,结构徐变应变次之;质量分数为12%时,结构徐变应变最小。通过钢管侧限对混凝土的套箍效应计算分析表明,在混凝土结构加载应力相同情况下,有钢管侧限的混凝土结构应力比小于无侧限的混凝土结构应力比;钢管侧限对混凝土的侧向约束增加,限制了混凝土纵向变形;随着应力比的减小,结构徐变变形减小。同时应用扫描电镜二次电子成像分析膨胀剂的作用机制得出：水泥浆中膨胀剂水化产生粗棒状、互相交叉的三硫型硫铝酸钙（AFt）结晶体,填充在原来被溶液占据的小孔里,使水泥石更密实。

英文摘要：

In order to study the effects of expansive agent dosage and lateral confinement by steel tube on creep strain of concrete,12 groups with or without lateral confinement of steel tube were conducted.The test results show that creep strain of concrete in lateral confinement by steel tube is 0.175-0.181 times of without lateral confinement at loading age to 480 days,and lateral confinement greatly reduces the creep strain of concrete.Three creep strains of concrete were tested under mass fraction of 4%,8% and 12% expansive agent dosage.The test results show that the expansive agent dosage is the same rule of creep strain effects on concrete in both lateral confinement and without lateral confinement of the concrete structure.When admixture is 4%,the creep strain of the structure is the biggest,and when admixture is 8%,creep strain of the structure take the second place.When admixture is12%,the creep strain of the structure is minimal.Stress ratio of concrete structure by steel tube lateral confinement is less than that without lateral confinement under the same load stress.Lateral restraint of concrete is increased by steel tube confinement,and the longitudinal deformation of concrete is confined.The smaller the stress ratio,thesmaller structure creep deformation.At the same time,the mechanism of the expansion agent was analyzed by scanning electron microscopy secondary electron imaging.The final analysis conclusion is that expansive agent in cement hydration produces three sulfur type calcium sulphoaluminate（AFt）crystals which is thick stick and cross each other.The AFt crystals fill in pores that it was occupied by a solution,which makes cement denser.