游离氧化钙在水泥浆体中的水化历程定量研究

Quantitative Study on Hydration Process of f CaO in Cement Paste

摘要:

在水泥浆体中掺入以氧化钙为主要组分的复合膨胀体系，采用化学分析（硝酸锶催化乙二醇乙醇苯甲酸法）和仪器分析（差示扫描量热（DSC））相结合的方法，测试水泥浆体中游离氧化钙（fCaO）的含量变化，并分析了氢氧化钙、碳酸钙和硫酸钙等水泥浆体中常见含钙矿物对测试结果的影响，获得了fCaO在水泥浆体中的水化反应程度随时间的变化规律.结果表明：膨胀熟料中的fCaO在水泥浆体中的反应极为迅速，在20℃恒温条件下，水胶比为04的水泥浆体加水搅拌2h后fCaO的水化反应程度即达到30%，1d反应程度即超过50%，7d基本反应完全.因而fCaO的水化膨胀作用主要发生在7d前，7d后的膨胀则主要来源于膨胀熟料中硫酸钙、硫铝酸钙等组分的继续水化.水泥浆体中葡萄糖酸钠缓凝剂的掺加对膨胀熟料中fCaO的水化反应有一定延迟作用，但效果有限.

Abstract:

A combination method of chemical analysis(strontium nitrate ethylene glycol ethanol benzoic acid) and thermal analysis(differential scanning calorimetry, DSC) was adopted to test the content of f CaO in cement paste added with or without a kind of composite expansive clinker with CaO as the main component, and the effect of calcium containing minerals in cement paste and expansive clinker including calcium hydroxide, calcium carbonate, calcium sulfate, etc., were analyzed, and finally, the reaction process of f CaO from composite expansive clinker in cement paste was obtained. The results show that the hydration of f CaO from expansive clinker is very rapid in cement paste, under the constant temperature of 20℃, the hydration degree reaches 30% at 2 h of curing, more than 50% of f CaO is reacted at 1d, and almost 100% of f CaO is reacted at 7d. Thus, the hydration of f CaO just generates expansion before 7d, and the expansion generated after 7d is mainly due to the hydration of calcium sulfate and calcium sulphoaluminate. The addition of sodium gluconate retarder in cement paste can delay the hydration of free calcium oxide in the expansion clinker, but the effect is limited.