再生混凝土早期抗开裂性能试验研究

采用刀口约束法试验,研究了再生粗骨料取代率及粉煤灰、矿粉的掺量对再生混凝土早期抗开裂性能的影响.以单位面积平板上的总开裂面积为主要指标评价了试件的抗开裂性能.研究表明,随着再生粗骨料取代率的增加,试件总开裂面积逐渐增大;取代率为100%的再生混凝土试件的总开裂面积是普通混凝土试件的1.5倍左右.掺入粉煤灰可以有效改善再生混凝土的抗开裂性能,当粉煤灰掺量达到30%时,试件的总开裂面积相比不掺矿物外加剂的对照组下降了72.1%.矿粉对于再生混凝土开裂面积的抑制作用不及粉煤灰有效,但其有助于减小裂缝分布的离散性.

Test of Cracking Resistance of Recycled Aggregate Concrete at Early Stage

The influence of the recycled coarse aggregate (RCA) replacement ratio, the amount of fly ash and slag powder on the cracking resistance of recycled aggregate concrete (RAC) during the early age was investigated by means of knife edge binding method in this paper. The total cracking area in flat of 1 m2 was applied as the main indicator to evaluate the cracking resistance for specimens. The results show that the total cracking area of RAC decreases with the increase of RCA replacement ratio. When the RCA replacement ratio reaches 100%, the total cracking area of RAC is 1.5 times that of natural aggregate concrete (NAC). The fly ash can effectively improve the cracking resistance of RAC. Compared to the control group without mineral admixture, the total cracking area of RAC specimens with fly ash accounting for 30% of the binder decreases by 72.1%. The effect of restraining the cracking area with slag powder is weaker than that with fly ash. However, the slag powder can decrease the discreteness of crack distribution.