Effects of Temperature on Mechanical Property of Set Cement and Analysis Thereof
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摘要: 为了表征长封固段固井水泥石在温度梯度下的机械性能，研究了不同温度下水泥石机械性能非线性变化规律并分析了原因。通过检测在用水泥石在30～160℃温度区间下的机械性能，分别建立了水泥石抗压强度、杨氏模量及泊松比随温度变化的关系曲线，同时拟合了水泥石机械性能随温度变化的函数关系式，并形成了考虑温度对水泥石机械性能影响的非线性物理方程；利用热重和XRD实验，对不同温度养护的水泥石进行了物性分析，通过SEM对水泥石的微观形貌进行了对比分析，初步探索了温度影响水泥石机械性能的内在原因。研究发现：相同养护天数下，水泥石在60℃及80℃条件下，机械性能存在突变区间，而80℃以上养护的水泥石其机械性能没有显著差异，同时发现温度介于突变区间以下，机械性能呈二次函数变化，高于突变区间则呈指数函数变化；结合微观分析结果发现，水泥石水化产物及水化程度的不同，是导致水泥石机械性能存在突变区间的原因。Abstract: To characterize the mechanical property of the long set cement under a certain temperature gradient, the nonlinear changing pattern of the mechanical property of set cement at different temperatures was studied, and the causes for the changing pattern was analyzed. Curves describing changes of compressive strength, Young's modulus and Poisson ratio with temperature were drawn using the mechanical properties of set cement at temperatures between 30℃ and 160℃, and a functional equation was established by fitting the mechanical property of set cement with temperature. A nonlinear physical equation taking into account the eff3ects of temperature on the mechanical property of set cement was formulated. Analyses of the physical properties of set cement cured at different temperatures were done with the data obtained through TGA and XRD experiments. Using SEM, the micro morphology of set cement was analyzed, and the inherent causes of temperature affecting the mechanical property of set cement were primarily studied. It was found that at the same time of curing, the mechanical property of set cement had sudden changes at 60℃ and 80℃. At temperatures over 80℃, no obvious difference in the mechanical property was found of the cured set cement. It was also found that at temperatures below the temperature at which the sudden change takes place, the mechanical property changes in a pattern of quadratic function; at temperatures above the temperature at which the sudden change takes place, the mechanical property changes in a pattern of exponential function. Combined with the data obtained from micro analyses, it was found that different hydration products of cement and the different degrees of hydration reactions are what cause the mechanical property of the set cement to have sudden changes.
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