配合比参数对混凝土热膨胀系数的影响

Effect of Mix Proportion on Coefficient of Thermal Expansion of Concrete

混凝土的热膨胀系数是体积稳定性的重要表征参数之一.采用正交设计的试验方法,研究了配合比设计参数对热膨胀系数的影响,并用功效系数法确定满足多项指标的优化配合比方案.试验结果表明,混凝土热膨胀系数随单位用水量、浆集比的增大而升高.水灰质量比的影响则取决于水泥用量和用水量的相对关系,当用水量一定时,热膨胀系数随水灰质量比的增大而降低;当水泥用量一定时,热膨胀系数随水灰质量比的增大而升高.热膨胀系数早龄期的变化较快,后期渐缓并趋于稳定.混凝土热膨胀系数与环境相对湿度有关,在75%时达到最大.

The coefficient of thermal expansion （CTE） is one of the most important indexes to volume stability of concrete. The method of orthogonal experimental design is adopted to study the effect of mix proportion on CTE of concrete. The laboratory-batched concrete specimens were moistured and tested at 1, 2, 3, 5, 7, 14, 28 days. The results show that CTE of concrete increases with the amount of water and paste-aggregate ratio. When the amount of water is fixed, CTE reduces with the increasing of water-cement ratio and increases when cement content is fixed. At first, the CTE changes dramatically, but 28 days later, it approaches a stable value, The CTE of concrete is subjected to moisture conditions at measurement, and reaches a maximum at relative humidity of 75 %. The optimized mix proportion can be determined by using value coeffieient to analyze the orthogonal results.