再生骨料级配对混凝土抗压强度的影响

Effects of Recycled Aggregates' Gradation on Compressive Strength of Concrete

对再生粗细骨料进行级配调整,并将调整前后的再生骨料分别用于制作再生混凝土立方体试块(共288个),研究级配调整对再生混凝土立方体抗压强度的影响,并探索级配调整前后再生混凝土立方体抗压强度变异现象及其规律。结果表明:按现行规范再生粗细骨料的级配不良时,人工级配调整可优化再生粗细骨料的级配,提高再生粗细骨料的堆积密度并降低压碎指标。级配调整前后的再生混凝土的立方体抗压强度总体上均随着再生粗骨料取代率的增加而下降,但再生粗骨料取代率50%时存在强度升高的变异现象。相同再生粗骨料取代率下抗压强度基本上呈正态分布,标准差在1.0~3.0 MPa之间。再生粗骨料的取代率为50%时,再生混凝土立方体抗压强度标准差比其他取代率下的标准差稍大,但仍小于3.0 MPa。骨料级配调整后的抗压强度标准差有大幅下降,意味着抗压强度的离散性得到大幅抑制。另外,将再生细骨料的取代率从0增加到30%,出现强度升高的变异现象。

Gradations of recycled coarse and fine aggregate(RCA and RFA) were modified,and then used to cast 288 recycled concrete(RC) cube specimens.The influence of gradation modification on cube compressive strength variability of RC and the related mechanism were studied.Results showed that the gradation curve of RCA and RFA was not fine enough according to the present codes,the gradation modification was a way to optimize the gradation curve of RCA and RFA,and the respective bulk density was increased and the crushing index was reduced.The cube compressive strength of RC decreased with the increase of the RCA replacement ratio in general,whereas the strength variability appeared when the RCA replacement ratio equaled 50%.The compressive strength showed normal distribution with the standard deviation ranged from 1.0 to 3.0 MPa.But the variability rose up with the standard deviation less than 3.0 MPa when the RCA replacement ratio was 50%.The standard deviation of RC compressive strength obviously decreased after the gradation modification,which meant that the scatter of the compressive strength was controlled.Besides,the variability of RC increased with the RFA replacement ratio increased from 0 to 30%.