The effects of two C 4A 3$-CaSO 4-CaO (CCC) systems were evaluated to explain the cause of water-loss-expansion of CCC systems introduced into concrete. This study measures the influences of two CCC systems on the concrete workability, compressive strength, autogenous shrinkage, dry shrinkage, hydration heat and XRD pattern. The results show that the CCC system can significantly compensate for concrete autogenous shrinkage and drying shrinkage, and that the CaO component of the CCC system is responsible for the water-loss-expansion behavior during drying. The dead burn during manufacturing or hindered hydration in low water-to-binder concrete allowed the CaO to continue to hydrate for unsaturated conditions while resulted in in-situ hydration and expansion. The results show the relationship between the CCC component activity and the expansive characteristics. Thus, CaO dead burn should be avoided and the CCC concentration should be reduced in low water-to-binder concrete.
摘要 该文分析了2种CCC (C 4A 3$-CaSO 4-CaO) 体系在混凝土中的作用效果, 揭示了掺入CCC体系的混凝土产生失水膨胀的原因。测试了2种CCC体系对混凝土工作性、抗压强度、自收缩和干燥收缩、水化热、XRD图谱的影响。CCC体系中的CaO组分由于制备阶段的死烧或低水胶比条件下水化过程受阻, 不能在水化早期阶段完成水化; 之后, 非饱水条件下CaO通过原位反应产生膨胀, 使得混凝土表现出失水膨胀现象。结果表明：CCC体系可有效补偿混凝土的自收缩和干燥收缩。研究结果揭示了CCC体系中组分活性与膨胀特性的关系。CCC体系制备过程中应避免对CaO组分的死烧; 同时, 低水胶比混凝土中应降低CCC体系的掺量。