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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。
In order to study the influence of different expansive agent mass fraction and steel tube confinement on creep strain of concrete, a total of 12 sets of concrete creep tests with and without steel tube were carried out. The results show that the creep strain of concrete confined with steel tubes is about 0.175 ~ 0.181 times of the creep strain without steel tube in test specimens loaded with the age of 480 days. The confined steel tube greatly reduces the creep strain of concrete . At the same time, three concrete creep tests with different mass fraction of swelling agent (mass fraction 4%, 8% and 12% respectively) were carried out. The results show that the relationship between the mass fraction of expansive agent and the concrete creep strain is as follows: the creep strain of concrete is the largest when the mass fraction is 4% Followed by strain; when the mass fraction is 12%, the creep strain is the smallest. The calculation and analysis of the ferrule effect of concrete confined by the confined steel tube shows that the stress ratio of the concrete confined by the steel tube is smaller than that of the unconfined concrete structure under the same loading stress of the concrete structure; Constraints increase, limiting the longitudinal deformation of concrete; as the stress ratio decreases, the structural deformation decreases. At the same time, the application of scanning electron microscopy to analyze the mechanism of expansive agent shows that the hydration of the expander in the cement slurry resulted in the formation of coarse rod-shaped and cross-linked trisulfide sodium sulfoaluminate (AFt) crystals filled in the original solution occupied Hole in the cement more compact.