粗骨料的分类及对再生混凝土抗压强度的影响

CLASSIFICATION OF COARSE AGGREGATES AND ITS EFFECT ON COMPRESSIVE STRENGTH OF RECYCLED AGGREGATE CONCRETE

通过比较我国关于天然和再生粗骨料的分类标准以及统计分析文献中的大量试验数据,指出我国不同标准间关于粗骨料的分类存在一定差异;结合所做的验证性试验结果,提出以吸水率和压碎指标为主要评价参数,对天然、再生及混合粗骨料（不同比例的天然和再生骨料的混合物）进行统一分类,并分析了再生及混合粗骨料类别对再生混凝土抗压强度的影响。研究结果表明：当选定天然骨料和再生骨料后,不同取代率下的混合骨料的吸水率和压碎指标可通过其与取代率之间的线性关系获得;当采用Ⅰ类、Ⅱ类和Ⅲ类再生骨料或混合骨料配制C35及其以下强度等级的再生混凝土时,再生混凝土的抗压强度可分别达同一配方基准普通混凝土强度的100%、90%以及80%以上,但用于配制C40—C60再生混凝土时,再生混凝土的强度可能会进一步降低约10%。

Through comparing the current classification standards for natural coarse aggregates（NCA） and recycled coarse aggregates（RCA）,and analyzing a great amount of experimental data from previous literatures,it was found that the coarse aggregate classification standards in different national codes were inconsistent. Based on the experimental results from the validation test by the authors,a uniform classification method was proposed for NCA,RCA and MCA（mixed coarse aggregates,namely the mixture of NCA and RCA with different proportions）,using the water absorption and crushing index of aggregates as the main classification indexes. Then the proposed classification on RCA and MCA was utilized to investigate the effect of RCA and MCA on compressive strength of recycled aggregate concrete. The results from the study showed that the water absorption and crushing index of MCA could be inferred from the corresponding values of NCA and RCA,and the linear relationship between the water absorption and crushing index of MCA with the proportion of RCA in MCA. When RCA and MCA of classⅠ,class Ⅱand class Ⅲ were used to produce C35 or below strength grade of concrete,the compressive strength of the recycled concrete could respectively reach not less than 100%,90% and 80% of the ordinary benchmark concrete with NCA. However,when RCA and MCA were used for the preparation of C40 to C60 concrete,the compressive strength of the recycled concrete might decrease further by 10%.