预湿再生细骨料对混凝土干缩及抗冻性能的影响

Influence of Pre-wetted Recycled Fine Aggregate on Drying Shrinkage and Freeze-thaw Resistance of Concrete

通过变化再生细骨料的预吸水程度及掺量研究预吸水再生细骨料对混凝土干缩及抗冻性能的影响,研究结果表明:掺加再生细骨料会造成混凝土的干缩值增大,但不同于普通混凝土,再生细骨料混凝土28d^120d完成了全部干缩值的70%~85%;当再生细骨料替代率和初始含水率分别为50%时,后期其收缩性能与普通混凝土最为接近;掺加再生细骨料会导致混凝土抗冻性能下降,再生细骨料初始含水率为50%的混凝土抗冻性能下降较小且随龄期的增长抗冻性能提高幅度较大;适度预吸水的再生细骨料可以发挥类似于"内养护"的作用,从而减小再生细骨料对混凝土收缩及抗冻性能的影响。

The influence of Pre-wetted recycled fine concrete is investigated through varying the moisture aggregate on drying shrinkage and freeze-thaw resistance of states and content of recycled fine aggregate. The results show that the larger drying shrinkage of concrete is caused by adding the recycled fine aggregate, and 70% -85% of the drying shrinkage of the recycled fine aggregate concrete are completed in 28d - 120d. The performance of mixes with 50% recycled fine aggregate at a 50% saturation level is similar to that of the normal concrete in the long term. The freeze-thaw resistance of concrete decrease when adding the recycled fine aggregate. The freeze-thaw resistance of concrete containing recycled fine aggregate at a 50% saturation level decrease less and increase more with the increase of curing period compared with other recycled fine aggregate concrete. In order to reducing the effect of recycled fine aggregate on drying shrinkage and freeze-thaw resistance of concrete, the recycled fine aggregate should be pre-wetted to achieve an appropriate saturation level, because the water stored in the recycled fine aggregate has a similar effect like ＂internal curing＂.