大坝混凝土早龄期温度变化下自收缩变形研究

Study of Self-Shrinkage Deformation of Dam Concrete under Early Age Temperature Change

采用温度匹配(TMC)和绝热两种温度养护模式,对某大坝混凝土(高粉煤灰掺量)开展温度-应力试验(TST)。结合温度匹配(TMC)和绝热养护情况下实际测量的自由试样的应变,得出大坝混凝土的一个系数(热膨胀系数)和一个规律(温度变形规律),结合两者分析温变环境下混凝土的收缩变形规律。研究结果表明,大坝混凝土的自收缩在早龄期会随时间变化而改变,温度变化过程会对其自收缩变形产生影响;对于同一种类别的混凝土,其自收缩在绝热模式和温度匹配模式情况下的发展规律存在差异,绝热模式要大于温度匹配模式;基于试验结果对比发现,现存的“等效龄期”预测法仍存在一些缺点,需要深入研究并改进。

Temperature-stress tests(TST) were conducted on Chenjiagou dam concrete(high fly ash admixture) using both temperature-matched(TMC) and adiabatic modes of temperature curing. A coefficient(thermal expansion coefficient) and a law(temperature deformation law) of the dam concrete were derived by combining the strains of the free specimens actually measured under temperature-matched(TMC) and adiabatic conditions, and the shrinkage deformation law of the concrete under the temperature change environment was analyzed by combining the two. The results of the study show that the self-shrinkage of dam concrete is time-varying at early ages and the temperature change process affects its self-shrinkage deformation. For the same type of concrete, there is a difference in the development law of self-shrinkage in the case of adiabatic mode and temperature matching mode, and the adiabatic mode is larger than the temperature matching mode. Finally, based on the experimental results, it is found that the existing “equivalent age” prediction method still has some shortcomings and needs to be studied and improved.