Since the existence of cement concrete, the early cracking problem of recycled concrete directly affects the application of concrete in engineering. Cracks can increase the permeability of concrete and lead to the decrease of structural durability of concrete in the corrosive environment. The reason causing this fatal problem is the shrinkage of concrete. The purpose of this paper is to improve the durability and integrity of concrete structure and understand its shrinkage. After the initial solidification and hardening of concrete, the volume deformation will cause the internal stress of the recycled concrete due to constraints. When the internal stress is greater than the tensile strength of recycled concrete, the recycled concrete will crack in the early stage. The study of early crack has always been the focus of scholars. Through the efforts of many scholars, factors leading to early cracking have been gradually discovered, such as hydration reaction of cement components in concrete, microstructure change, and external environment. In this paper, the influence of chemical shrinkage and temperature shrinkage on the early cracking of recycled concrete is analyzed by studying the chemical composition of the raw material of recycled concrete for chemical experiments and comparing the recycled concrete in a constant temperature studio with different temperatures. It is concluded that the composition of concrete and the content of each component have direct influence on the chemistry. Concrete containing more C3A has greater chemical reduction. Temperature difference is the main factor causing temperature shrinkage, including the heat released by component hydration. In addition to the change in the external temperature, the temperature of the concrete will also decrease, leading to early cracking.

中文翻译：

---

化学收缩率和温度收缩率对再生混凝土早期开裂的影响

由于存在水泥混凝土，再生混凝土的早期开裂问题直接影响到混凝土在工程中的应用。裂缝会增加混凝土的渗透性，并导致其在腐蚀性环境中的结构耐久性下降。导致此致命问题的原因是混凝土的收缩。本文的目的是提高混凝土结构的耐久性和完整性，并了解其收缩率。在混凝土初步固化和硬化后，由于约束，体积变形将引起再生混凝土的内应力。当内部应力大于再生混凝土的抗张强度时，再生混凝土将在早期破裂。早期裂纹的研究一直是学者关注的焦点。经过许多学者的努力，逐渐发现了导致早期开裂的因素，例如混凝土中水泥成分的水合反应，微观结构变化和外部环境。通过研究化学实验中再生混凝土原料的化学成分，并比较不同温度下的恒温工作室中的再生混凝土，分析了化学收缩和温度收缩对再生混凝土早期开裂的影响。结论是，混凝土的组成和每种成分的含量对化学性质有直接影响。包含更多C3A的混凝土具有更大的化学还原性。温差是引起温度收缩的主要因素，包括组分水合作用释放的热量。