The inherent inferior quality of recycled coarse aggregate (RCA) influences the microstructural characteristics and consequently, the macro-mechanical properties of recycled aggregate concrete (RAC). The present paper investigates the influence of aggregate properties, degree of hydration ($\alpha$), and micro and meso level characteristics of concrete on its compressive strength. Moreover, the influence of different mix design methods (conventional and Particle Packing Method) and mixing approaches (normal mixing approach and two stage mixing approach) on $\alpha$, and micro and meso level properties of concrete are analysed. In addition to the crushing value and water absorption of coarse aggregate, thermogravimetric analysis, nanoindentation and image analysis of back-scattered electrons images and X-ray microtomography images are performed to measure $\alpha$, interfacial transition zone (ITZ) thickness, voids content in the ITZ and interface of concrete, respectively. However, none of these parameters can be singled out to demonstrate its major or significant contribution to the compressive strength of concrete. Hence, the influence of each parameter must be appreciated. An expression is proposed by accounting each of these parameters and also the cement content and coarse aggregate fraction to predict the compressive strength of concrete, which exhibits good correlation with the experimental results.

再生粗骨料（RCA）的固有劣质影响了再生骨料混凝土（RAC）的微观结构特性，进而影响其宏观力学性能。本文研究了骨料性能，水合度（$\alpha$），以及混凝土的微观和中观水平特性对它的抗压强度的影响。此外，不同的混合设计方法（常规和颗粒堆积方法）和混合方法（常规混合方法和两阶段混合方法）对$\alpha$，并分析了混凝土的微观和中观水平特性。除粗骨料的破碎值和吸水率外，还进行了热重分析，反向压痕电子图像和X射线显微断层图像的纳米压痕和图像分析，以测量$\alpha$，界面过渡区（ITZ）厚度，ITZ和混凝土界面中的空隙含量。然而，这些参数中没有一个可以被选出来证明其对混凝土抗压强度的主要或重要贡献。因此，必须了解每个参数的影响。通过考虑这些参数中的每一个以及水泥含量和粗骨料分数来提出一个表达式，以预测混凝土的抗压强度，与实验结果具有很好的相关性。