冻融损伤对再生混凝土耐久性及与钢筋粘结性能分析

制作掺入引气剂和未掺入引气剂的100%粗骨料取代率的再生混凝土RC1和RC2两组试件以及掺入引气剂和未掺入引气剂的普通混凝土NC1和NC2两组试件,并分别对经过不同次数冻融循环试件的抗压强度、质量损失率、动弹性模量损失率进行研究。结果表明,冻融后各组试件的抗压强度、质量损失率及动弹性模量损失率均降低,对于添加引气剂的NC1和RC1两组试件损失较小,其中RC1组试件在200次冻融后抗压强度损失接近40%,质量损失率达0.5%,动弹性模量损失率38.5%。100%取代率并加入引气剂的ZRC组试件冻融后进行中心拨出实验,发生劈裂破坏和钢筋拔出破坏2种形式。再生粗骨料混凝土与钢筋的极限粘结应力均随冻融次数的增加而降低,200次冻融后极限粘结应力下降33.5,荷载滑移曲线既有上升段也有下降段。

Effect of the freeze-thaw damage on the durability of recycledconcrete and the bonding performance of steel

Four groups of concrete test-pieces were made. The first two group test-pieces, RC1 and RC2, were made from recycled 100% coarse aggregate concrete with and without air-entraining agent respectively. The second two group test-pieces, NC1 and NC2, were made from common concrete with and without air-entraining agent respectively. Then, we studied the compressive strength, the mass loss rate and the dynamic elastic modulus loss rate of the test-pieces after different times of freeze-thaw cycles. It is shown that the compressive strength, the mass loss rate and the dynamic elastic modulus loss rate of all groups reduce after freeze-thaw. While these parameters of NC1 and RC1 which contain air-entraining agent decrease less. After 200 times of freeze-thaw cycles, the loss of the compressive strength of RC1 is close to 40%, the mass loss rate is 0.5%, and the loss rate of the dynamic elastic modulus is 38.5%. Another group of test-pieces, ZRC, which has the same components as RC1, were used for center drawing tests. And it''s found that there are two forms of damage, splitting failure and steel pull-out damage, after freeze-thaw cycles. The ultimate bond stress between recycled coarse aggregate concrete and reinforcing bar reduces as the times of freeze-thaw cycles increase. After 200 times of freeze-thaw cycles, the ultimate bond stress reduced 33.5%. There is a rising section and a descending section in the load-slip curve.