不同超低温作用工况混凝土受拉受压强度间关系试验研究

Experimental study on relationship between tensile and compressive strengths of concrete under different ultralow temperature action conditions

通过常温降至给定超低温(-40℃、-80℃、-120℃、-160℃和-190℃)以及经历超低温再直接和以1℃/min匀速地回至常温共3种工况混凝土的轴心受压和劈裂抗拉试验,探讨不同超低温作用工况下混凝土受拉受压强度间关系及其离散性变化情况。结果表明,随作用的超低温降低,混凝土超低温时相对受拉受压强度及其差值比分别呈先增后减、波动地增大和先增后减的变化趋势;经历超低温再直接回至常温工况混凝土相对受拉受压强度及其差值比分别呈波动状但较为平稳、先增大后平稳和先减后增的变化趋势;而经历超低温再以1℃/min匀速地回至常温工况混凝土相对受拉受压强度则均呈波动状且稍有增大的变化趋势。混凝土超低温时受拉受压强度离散性随作用的超低温降低分别呈先迅速后缓慢减小和缓慢增大的变化趋势;而经历超低温再直接和以1℃/min匀速地回至常温工况混凝土的受拉强度离散性却总是大于受压强度,但两者均呈波动性减小的变化趋势。

The relationship between tensile and compressive strengths and their discreteness of concrete subjected to different ultralow temperature action conditions are discussed in this paper through axial compression and splitting tensile experiments of concrete under three temperature action conditions: cooling to given ultralow temperatures(-40 ℃,-80 ℃,-120 ℃,-160 ℃and-190 ℃) from room temperature, and returning to room temperature directly and at a rate of1 ℃/min respectively after experiencing given ultralow temperatures. The results show that with the decrease in the ultralow temperature, for the concrete at ultralow temperature, its relative tensile strength increases first and then decreases, and its relative compressive strength increases in fluctuation, and the difference ratio of their relative tensile and compressive strengths increases first and then decreases;for the concrete subjected to returning to room temperature directly from ultralow temperatures, its relative tensile strength shows a trend of stable fluctuation, and its relative compressive strength first increases and then stabilizes, and the difference ratio of their relative tensile and compressive strengths first decreases and then increases;while for the concrete subjected to returning to room temperature at a rate of 1 ℃/min from ultralow temperatures, their relative tensile and compressive strengths show a fluctuating and slightly increasing trend. With the decrease in the ultralow temperature, the tensile strength discreteness of concrete at ultralow temperature decreases rapidly first and then slowly, while its compressive strength discreteness increases slowly. However, the tensile strength discreteness of concrete subjected to returning to room temperature directly and at a rate of 1 ℃/min respectively from the ultralow temperatures is always greater than its compressive strength discreteness, but both show a trend of decreasing fluctuation.