冻融循环后再生混凝土力学性能试验研究

为了研究再生混凝土冻融循环后的力学性能变化，通过改变冻融循环次数，对不同强度的再生混凝土和普通混凝土的抗冻性能进行试验研究，分析混凝土立方体抗压强度、质量、动弹性模量及超声波损失率的变化规律，并针对内蒙古地区，对不同强度的再生混凝土进行了抗冻耐久性寿命预测，同时对达到寿命服役期的最大抗压强度损失率给出了建议。研究结果表明：冻融循环50次前，再生混凝土与相同强度等级的普通混凝土的抗冻性能相差不大，冻融循环50次后，再生混凝土的抗冻性能略低于普通混凝土的，且随着冻融循环次数的增加，再生混凝土抗冻性能的劣势越来越显著；强度等级对再生混凝土试件的抗冻性能影响较大，强度等级越低，再生混凝土的冻融损伤越严重；超声波对冻融循环作用下再生混凝土的损伤较动弹性模量法更为敏感，建立的冻融损伤模型能够较好地反映再生混凝土冻融循环后的力学性能变化规律。

Experimental study on mechanical properties of recycledconcrete after freeze-thaw cycles

In order to study the mechanical properties of recycled concrete after freeze-thaw cycles, an experimental study on the frost resistance of recycled concretes and ordinary concretes with various strength grades was conducted by changing the number of freeze-thaw cycles. The rule of changes of the cube compressive strength, mass, dynamic elastic modulus and ultrasonic loss rate of the specimens with the freeze-thaw cycles was analyzed. The anti-freeze durability lives of recycled concretes with different strength grades were predicted for the Inner Mongolia area, and the maximum loss rate of compressive strength over the service life was suggested. The results of the present research show that there is no significant difference in the frost resistance between the recycled concrete and the ordinary concrete with the same strength grade before 50 freeze-thaw cycles, and the frost resistance of the recycled concrete is lower than the ordinary concrete after 50 freeze-thaw cycles. With the increase of the number of freeze-thaw cycles, the relatively poor anti-freeze performance of the recycled concrete becomes increasingly obvious. The strength grade has a significant effect on the properties of the recycled concrete specimens. Under the effects of freeze-thaw cycles, the damage of the recycled concrete is more severe for a lower strength grade. Ultrasound wave is more sensitive than the resonance method for the damage of recycled concrete under freeze-thaw cycles. The freeze-thaw damage model established in the present study can reasonably reflect the rule of changes of mechanical properties of recycled concrete after freeze-thaw cycles.