This paper investigates the influence of aggregate packing optimization based on a particle packing method (PPM) and cement paste volume (CPV) on the workability and mechanical properties of both natural aggregate concrete (NAC) and recycled aggregate concrete (RAC). The slump, compressive strength, flexural strength and Young's modulus of concrete were first examined, followed with the characterization of macro-pore structure inside RAC by using X-ray computed tomography (CT). The results indicate that the PPM can help to densify the granular skeleton of aggregates in concrete by reducing the void around the aggregates and the cement paste film thickness, and subsequently enhances the mechanical properties of the concrete with a constant CPV. This enhancement is higher for RAC than NAC, particularly for the Young's modulus. The particle packing optimization can also decrease the number of macro pores in RAC, contributing to the enhancement in the mechanical properties of RAC. Moreover, increasing CPV in concrete with a maximum aggregate packing status considerably decreases the mechanical properties of concrete, whereas increases its workability. This is mainly caused by the increased number of macro pores in the cement paste and at the interfaces between RCAs and hardened cement paste.

中文翻译：

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骨料填充优化和水泥浆体积对天然和再生骨料混凝土性能的影响

本文研究了基于颗粒填充法 (PPM) 和水泥浆体积 (CPV) 的骨料填充优化对天然骨料混凝土 (NAC) 和再生骨料混凝土 (RAC) 的和易性和力学性能的影响。首先检测混凝土的坍落度、抗压强度、抗弯强度和杨氏模量，然后使用 X 射线计算机断层扫描 (CT) 表征 RAC 内部的宏观孔隙结构。结果表明，PPM可以通过减少骨料周围的空隙和水泥浆膜厚度来帮助致密混凝土中骨料的粒状骨架，从而在恒定CPV下提高混凝土的力学性能。这种增强对于 RAC 比 NAC 更高，特别是对于杨氏模量。颗粒堆积优化还可以减少 RAC 中的大孔数量，有助于提高 RAC 的机械性能。此外，在具有最大集料填充状态的混凝土中增加 CPV 会显着降低混凝土的力学性能，但会增加其和易性。这主要是由于水泥浆体中以及 RCA 与硬化水泥浆体之间的界面处的大孔数量增加所致。