再生混凝土长龄期强度与收缩徐变性能

Long-term Strength,Shrinkage and Creep Properties of Recycled Aggregate Concrete

通过改变再生粗骨料取代率,并考虑引气剂的影响,对再生混凝土长龄期下的立方体抗压强度和收缩性能进行试验;采用不同的加载龄期,对再生粗骨料取代率为50%的再生混凝土徐变性能进行试验研究;建立了再生混凝土长龄期强度推算公式。结果表明:长龄期下再生混凝土的立方体抗压强度变化规律与普通混凝土基本一致,28d龄期再生混凝土的立方体抗压强度随再生粗骨料取代率的增加而降低;再生混凝土的收缩随再生粗骨料取代率的增加而增加,添加粉煤灰、矿粉等矿物外掺料可以使再生混凝土收缩降低;加载龄期对于再生混凝土徐变值有影响,加载龄期越早,再生混凝土徐变值越大;利用所建立的强度推算公式计算得到的强度值与试验结果比较吻合,并且优于欧洲CEB-FIP Model Code 1990规范建议公式的计算结果。

The effects of the recycled coarse aggregate（RCA）replacement ratio and air‐entraining agent on cube compressive strength and shrinkage of recycled aggregate concrete（RAC） were experimentally investigated .The creep of RAC with 50% RCA replacement ratio was also studied by varying the loading time .Meanwhile ,the calculation formula for the compressive strength of RAC at various ages was established .The experimental results reveal that the long‐term strength increasing rule of RAC is similar to that of natural aggregate concrete .The cube compressive strength of RAC at 28 d reduces whereas the shrinkage increases with the increase of RCA replacement ratio . In addition , adding reasonable amount of slag and fly ash can reduce the shrinkage of RAC .The loading time has an effect on the creep of RAC as the creep is greater when the specimens are loaded at an earlier age .The compressive strength values calculated by the proposed formula are in good agreement with the experiment results and more accurate than the outcomes deprived from the suggested formula in CEB‐FIP Model Code 1990 .