D型速凝剂对喷射混凝土微观结构和力学性能的影响

Effects of D-accelerating Agent on Microstructure and Mechanical Properties of Shotcrete

为了研究D型速凝剂对喷射混凝土微观结构的影响,通过扫描电子显微镜(SEM)、X射线衍射(XRD)和水泥稠凝测定仪等研究手段对喷射混凝土中主要胶凝材料的微观形貌、晶体结构及初凝时间等进行测试。研究结果表明,D型速凝剂的促凝效果良好,水化早期,D型速凝剂促使水泥石产生CaCO_3晶体、AFt晶体和C-S-H凝胶等水化产物,水泥石结构密实,这使得喷射混凝土早期强度上升较快;水化中后期,水泥石收缩较大,出现微裂缝,结构较松散,这影响了喷射混凝土中后期强度。

In order to study the effects of D-accelerating agent on microstructure of shotcrete,Microcrystal structure,morphology and initial setting time of gelled materials in shotcrete were characterized by using X-ray diffraction（ XRD）,scanning electron microscopy（ SEM） and Vicat apparatus. The results showed that D-accelerating agent has excellent quick setting characteristics. During the early hydration,D-accelerating agent promotes cement to create the hydration products including the crystals of CaCO_3,AFt and C-S-H,and the microstructure of hardened cement paste is close-grained relatively. These characteristics make early strength of shotcrete rising rapidly. During the later hydration,the shrink of hardened cement paste leads to the micro-cracks and its microstructure is loose. This affects the middle and later strength of shotcrete.