基于毛细管负压技术测试混凝土最早期的自干燥效应

VERY EARLY AGE SELF-DESICCATION EFFECT MEASUREMENT BASED ON MENISCUS DEPRESSION TECHNOLOGY FOR CONCRETE

混凝土自干燥收缩与其内部相对湿度的下降密切相关。低水胶比混凝土在结构形成以后的初始阶段存在较大的自干燥收缩,但通常此时混凝土内部相对湿度较高,采用传统的湿度计难以测试出其自干燥效应。借鉴了土壤物理学中张力计的基本原理,研制开发了最早期毛细管负压自动测试系统,结合Laplace方程和Kelvin定律,实现了从浇筑成型开始至终凝后混凝土内部自干燥效应的自动化测试,提出了自干燥收缩零点判定的新方法。

The self-desiccation shrinkage of concrete is closely related to the drop of its internal relative humidity. Substantial self-desiccation shrinkage exists in concrete with low water-binder ratio at very early age as its structural forms. However, the internal relative humidity is still too high for self-desiccation to be tested by a conventional hygrometer. The concept of tensiometer in soil physics was used for reference for the development of an automated meniscus depression measuring system for the very early age concrete. Combined with the Laplace formula and Kelvin law, not only the automated testing of the interior self-desiccation effect of the concrete from immediately after the casting to several hours after initial setting was realized, but also a new method for the determination the time zero of self-desiccation shrinkage was put forward.