新型速凝剂水化机理及工程特性试验研究

喷射混凝土是矿山法修建隧道的基本措施,速凝剂作为喷射混凝土必需的外加剂,对工程质量和经济效益具有重要影响。结合正在建设的某高地应力软岩隧道,分析碱性(Na~+·AlO_2~-溶液)和非碱性(Al~(3+)·SO_4~(2-)溶液)速凝剂的促凝机理,并开展新型碱性液体速凝剂的室内试验和现场湿喷试验,得出如下结论:(1)碱性速凝剂和非碱性速凝剂的促凝机理都是利用活性Al~(3+)的水化反应;(2)碱性速凝剂产生粉尘主要是由于超量的Na~+中断了水泥的水化反应,非碱性速凝剂是由于SO_4~(2+)中断了水泥的水化反应;(3)新型碱性速凝剂最大的特点是降低了Na~+/Al~(3+)的摩尔比(1.19∶1),具有无毒无味、掺量少、落浆回弹少、早强且后期强度损失少等优点,是一种理想的喷射混凝土用速凝剂。

Experimental Study on Hydration Mechanism and Engineering Characteristics of New Accelerator

Shotcrete is a basic means of tunnel construction by mining method. As a necessary admixture of shotcrete, accelerator has important influence on the quality and economic benefits of the project. In this paper, the mechanism of alkaline and alkali-free accelerator are analyzed. Furthermore, the indoor and in-situ experiments of the new alkaline liquid accelerator are carried out in the construction of a high geo-stress soft rock tunnel. The following conclusions could be drawn:(1)Both the mechanism of alkaline and alkali-free accelerator are taking the advantage of Al~(3+) hydration reaction;(2)The dust produced by the alkaline accelerator is resulted from the excessive interruption of hydration reaction of cement Na~+; while the dust generated by the alkaline-free accelerator is resulted from the interruption of the hydration reaction of cement SO_4~(2-).(3)The main advantage of the new liquid accelerator is the reduction of molar ratio Na~+/Al~(3+)(1.19∶1), it is characterized by nontoxic and tasteless, low dosage, shorter setting time, less rebound droplet and less strength loss in later period. Conclusively, this novel admixture is an ideal accelerator for shotcrete in soft rock tunnel.