The use of recycled coarse aggregate (RCA) in natural aggregate concrete is a sustainable solution to the problem of solid waste worldwide. The effects of RCA gradation, RCA content, fly ash content and water–cement ratio (w/c) on mechanical properties of RCA are studied in this paper. The stress–strain curves of each specimen under 28 days axial loads were obtained by experiments. Through the stress–strain curves of each specimen, the effects of the above four factors on the maximum strain, ultimate strain, elastic modulus and toughness index of RAC were analyzed, and the optimal selection of the four factors were determined. Mathematical models of strength and four factors were established by fitting the experimental data. Finally, the RAC’s hydration failure mechanism with different RCA contents was studied by scanning electron microscopy. The test results show that: influence degree of the four factors on the compressive strength of RAC is: w/c > RCA content > RCA gradation > fly ash content. Based on a comprehensive analysis of compressive strength, peak strain, ultimate strain, elastic modulus and toughness index, it is recommended that RCA gradation is 5–20 and 5.0–31.5, RCA content is 50–70% and fly ash content is 20%.

中文翻译：

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基于正交分析的再生骨料混凝土应力应变关系分析

在天然骨料混凝土中使用再生粗骨料（RCA）是解决全球固体废物问题的可持续解决方案。研究了RCA等级，RCA含量，粉煤灰含量和水灰比（w / c）对RCA力学性能的影响。通过实验获得了在28天轴向载荷下每个试样的应力-应变曲线。通过每个试样的应力-应变曲线，分析了上述四个因素对RAC的最大应变，极限应变，弹性模量和韧性指数的影响，并确定了四个因素的最佳选择。通过拟合实验数据建立了强度和四个因素的数学模型。最后，通过扫描电子显微镜研究了不同RCA含量下RAC的水化破坏机理。试验结果表明：四个因素对RAC抗压强度的影响程度为：w / c> RCA含量> RCA级配>粉煤灰含量。在对抗压强度，峰值应变，极限应变，弹性模量和韧性指数进行综合分析的基础上，建议RCA等级为5-20和5.0-31.5，RCA含量为50-70％，粉煤灰含量为20％ 。