新浇筑混凝土热学参数现场试验与分析

In-situ Test and Analysis of Thermal Parameters of Freshly Poured Concrete

寒冷地区自然入仓情况下混凝土浇筑温度难以得到保障,高拱坝需要较好的完整性才能保障结构的安全,不建议长间歇,由此需要准确地计算分析寒冷地区极端条件下的浇筑温度保障措施。由于新鲜混凝土自由水分含量与老混凝土存在较大区别,因此新浇筑混凝土表面等效热交换系数、导热系数、导温系数与老混凝土也可能存在较大差别,需要进行试验确定。因此,针对新浇筑混凝土布置试验,对距离坯层表面不同位置混凝土温度进行监测,提出相应的参数反演方法,对混凝土导热系数、导温系数和表面等效热交换系数进行反演分析。结果表明,新浇筑混凝土表面等效热交换系数、导热系数、导温系数与老混凝土存在较大差别,导热系数和导温系数为老混凝土的1.67倍,裸露时新浇筑混凝土表面等效热交换系数则为老混凝土的7.78倍。这些差异造成的计算误差足以影响施工措施的制定。该试验结果可以为坯层浇筑期间混凝土温度变化计算提供参考。

It is difficult to ensure the pouring temperature of concrete under natural conditions in cold regions.High arch dams need good integrity to ensure the safety of the structure,and it is not recommended to have a long-time interval.Therefore,it is necessary to accurately analyze the pouring temperature guarantee measures under extreme conditions in these regions.Since the free water content of freshly poured concrete is quite different from that of mature concrete,the surface convection coefficient,thermal conductivity coefficient,thermal conductivity coefficient and mature concrete also may be quite different,which needs to be determined by test.This paper arranged test to monitor the temperature of concrete at different locations from the surface of the concrete layer,and proposed the corresponding parameter inversion method to inverse the thermal conductivity,thermal conductivity and surface convection coefficient of concrete.The results show that the surface convection coefficient,thermal conductivity coefficient and thermal conductivity coefficient of the freshly poured concrete are significantly different from that of the mature concrete.The thermal conductivity coefficient and thermal conductivity coefficient are 1.67 times of the mature concrete,and the surface convection coefficient of the freshly poured concrete is 7.78 times of the mature concrete when exposed.The calculation error caused by these differences is enough to affect the construction measures.The test results can provide a reference for the calculation of concrete temperature change during pouring concrete layer.