冻融循环后全级配混凝土及其湿筛混凝土的力学性能比较

对全级配混凝土试件及其湿筛混凝土试件分别进行0、50、100、150、200、250和300次快速冻融循环试验。观察冻融后试件外观的变化情况,测定冻融循环后全级配混凝土和湿筛混凝土的抗压强度与抗拉强度,讨论了冻融循环对抗压强度、抗拉强度及其应力应变关系的影响。试验发现,冻融循环后全级配混凝土的外观破损情况较湿筛混凝土严重得多。试验结果表明,随冻融次数增加,全级配混凝土与湿筛混凝土的抗压强度与抗拉强度均明显降低,但全级配混凝土的降低值较湿筛混凝土的降低值大,特别是抗拉强度,降低幅度更大。两种混凝土单轴压应力应变曲线峰值应力点随冻融循环次数增加逐渐向右下方偏移,曲线形状变得扁平,而其单轴拉应力应变曲线峰值应力点随冻融循环次数增加逐渐向左下方移动,曲线变短。通过对试验结果的分析,建立了全级配混凝土和湿筛混凝土之间单轴压及单轴拉关系的数学公式,可以为寒冷地区大坝、海洋平台等的设计、维修、维护及其寿命预测等提供理论依据。

Comparison of mechanical properties of fully-graded concrete and wet-screened concrete

Freeze-thaw tests were carried out for fully-graded and its wet-screened concrete specimens with number of freeze-thaw cycles of 0, 50, 100, 150, 200, 250, 300 times to observe the surface form changes of specimens’ surface form. The uniaxial compression and tension tests were carried out for fully-graded and its wet-screened concrete after different freeze-thaw cycles. The influence of freeze-thaw cycles on compressive and tensile strength and relationship of stress-strain were analyzed. Based on the tests, the surfaces of fully-graded concrete were damaged badly than that of wet-screened concrete after the same freeze-thaw cycles. The uniaxial compressive and tensile strength of fully-graded and its wet-screened concrete specimens became smaller as freeze-thaw cycles increased, and fully-graded concrete strength decreased more than that of wet-screened concrete, with especially tensile strength. The peak stress points on compressive stress-strain curves of the two kinds of concrete shift to the right, and curves shape became flatter as freeze-thaw cycles increasing. On the contrary, the peak stress points on tensile stress-strain curves of these two kinds of concrete shift to the left, and curves became shorter as freeze-thaw cycles increasing. Based on the experimental data, some formulas relating to uniaxial compression and tension between fully-graded and its wet-screened concrete were proposed. It provides the reference for the maintenance, design and the life prediction of dams, offshore platforms in cold weather.