不同水灰比混凝土自干燥试验

为研究不同水灰比水工混凝土和高性能混凝土内部自干燥效应,对水灰比0.33、0.41、0.50的水工混凝土试件和0.30、0.40、0.50的高性能混凝土试件进行密封包裹,并开展持续3个月的内部相对湿度监测。试验结果表明,在密封状态下,水工混凝土和高性能混凝土内部相对湿度均存在两个时期,即湿度饱和期和湿度下降期;随着水灰比的减小,湿度饱和期持续的时间逐渐减小;相同水灰比下,高性能混凝土的内部相对湿度比水工混凝土的内部相对湿度下降快,湿度饱和期持续时间更短。在密封状态下,0.50水灰比的水工混凝土的内部相对湿度基本无下降;但0.41水灰比的水工混凝土存在缓慢的自干燥效应。当混凝土缓慢失水干燥时,混凝土将会出现缓慢收缩,这为解析溪洛渡特高坝工程扣除温度分量的无应力计变形测值长期不稳定的机制提供了一种新思路。

Discussion on self-drying test of concrete with different water-cement ratios

To investigate the internal self-drying effects of hydraulic concrete and high-performance concrete with different water-cement ratios, the ratios are set to be 0. 33, 0. 41, 0. 51 for hydraulic concrete and 0. 30, 0. 40, 0. 50 for high-performance concrete. The concrete specimens were sealed and the internal relatively humidity inside was monitored for three months. The test results show that the internal relative humidity for both hydraulic and high-performance concrete in the sealed state has two periods, namely the humidity saturation period and the humidity drop period. As the water-cement ratio decreases, the duration of the humidity saturation period gradually decreases. The drop rate of the relative humidity for high-performance concrete is higher than that for hydraulic concrete with the same water-cement ratio, and the duration of humidity saturation period for the former is shorter. The internal relative humidity of hydraulic concrete with the water-cement ratio 0. 5 in the sealed state does not drop substantially but with the water-cement ratio 0. 41, it drops slowly due to the self-drying effect. When the concrete dries gradually, it shrinks slowly, which provides a new idea to analyze the long-term instability mechanism for the strain with the deduction of temperature strain, called the no-stress-gauge strain in the Xiluodu ultra-high dam project.