铝酸钠液体速凝剂性能及作用机理

目的研究不同物质的量比铝酸钠液体速凝剂对水泥性能的影响规律，探讨其促凝机理及存在最佳掺量的原因．方法测试了不同物质的量比的铝酸钠液体速凝剂对水泥的凝结时间和强度，利用差热分析，X-射线衍射和扫面电镜手段分析其作用机理．结果物质的量比为1．2时．铝酸钠液体速凝剂放置1d便产生大量的沉淀．增大物质的量比时，稳定性也增加．不同物质的量比的铝酸钠液体速凝剂均存在最佳掺量，其凝结时间和强度都符合JC477—2005标准．结论铝酸钠液体速凝剂并不是靠生成大量钙矾石相互搭接实现速凝，而是促进各水泥矿物的反应形成大量的凝胶，并有一定量的板状晶体氢氧化钙和柱状晶体钙矾石（AFt）分布在其中．当掺量过大时，形成大量的六方片状晶体水铝石和单硫型水化硫铝酸钙（AFm），C—S—H凝胶和柱状钙矾石相对较少，导致结构不密实，速凝效果减弱．

Study on the Performance and Mechanism of the Liquid Sodium Aluminate Accelerated Agent

The influence law of the different mole ratio liquid sodium aluminate accelerated agent on the cement performance was studied and its acceleration mechanism and the reason of existing optimum mix amount were investigated. The setting time and strength of the different mole ratio liquid sodium aluminate accelerated agent on the cement were measured. Mechanism was analyzed by DTA, X-ray and scanning electron microscopy. When the mole ratio was 1.2 and the liquid sodium aluminate accelerated agent was placed 1 day ,large amounts of precipitation would be produced. The stability was increased as the mole ratio increased. Different mole ratio liquid sodium aluminate accelerated agent had an optimum mix amount and it＇s setting time and strength accord with the standard of JC477 -2005. The mechanism of the different mole ratio liquid sodium aluminate accelerated agent was formed not by the formation of large quantity of ettringite but by promoting the reaction of cement minerals formatting lots of gel, and a certain amount of the platy crystals calcium hydroxide and columnar crystals ettringite （AFt）distributing were among them, thus resulting in rapid setting. When mixing amount superfluous, lots of hexagonal aluminate hydrates and monosulfate were formed and calcium silicate hydrate gel and columnar crystal ettringite were less, causing imperfect structure, the effect of the liquid accelerated agent was reduced.