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