考虑温度历程的早龄期大坝混凝土自生体积变形分离方法现场试验

混凝土在水化过程中会产生自生体积变形和温度应变等现象,与混凝土的耐久性有着密切联系,为工程建设各方所关注。对此,在西南某混凝土特高拱坝混凝土浇筑现场,采用无应力计对冷却水管周围两处不同位置处早龄期混凝土的应变进行现场监测,运用成熟度理论考虑混凝土的温度历程对混凝土水化进程的影响,采取一种新方法将总应变计算式解耦,从而摆脱对早龄期混凝土的热膨胀系数为定值的依赖,得出混凝土热膨胀系数在等效龄期下的历程,最终从无应力计变形监测值中分离出温度应变和自生体积变形。试验结果表明:这种方法能考虑混凝土温度因素,精确便捷地对早龄期混凝土的热膨胀系数以及自生体积变形进行分离,给现场混凝土的养护以及防裂施工提供指导。

Field Test on the Separation of Autogenous Deformation of Dam Concrete at Early Age Considering Temperature History

Concrete undergoes autogenous deformation and temperature deformation during its hydration advancement, which is closely linked with the durability of concrete and is concerned by engineering construction parties. Based on this, two stress-free meters that located on different places around the cooling pipe in a southwest concrete extra-high arch dam construction site were used to monitor the total deformations, a new method considering the concrete temperature history was adopted for decoupling the monitored deformations, this method could avoid the dependence on taking thermal expansion coefficient of early age concrete as a constant value, thus, the curve of thermal expansion coefficient vs. equivalent age was got and finally temperature deformation and autogenous deformation were separated from the data. It is indicated by test results that the method could consider temperature history, separate the thermal expansion coefficient and autogenous deformation of concrete at early age more precisely and easily, and also could provide guidance for the site concrete curing and anti-crack constructions.