粉煤灰与矿渣的早期火山灰反应放热行为及其机理

Behavior and Mechanism of Pozzolanic Reaction Heat of Fly Ash and Ground Granulated Blastfurnace Slag at Early Age

针对大体积混凝土绝热温升计算中粉煤灰与矿渣的火山灰反应放热问题,利用微量热仪法测试了不同掺量粉煤灰和矿渣对水泥水化热及放热速率的影响规律,分析了粉煤灰和矿渣水化3 d以前的火山灰反应放热行为,采用X射线衍射与差示扫描量热–热重法研究了粉煤灰与矿渣对水泥早期水化及其火山灰放热行为的影响机理。结果表明:粉煤灰与矿渣水化3d时火山灰反应热分别约为3～5J/g和15～16J/g。粉煤灰对水泥水化的阻碍作用在水化24h前最为明显,其火山灰效应主要发生于水化24h之后;矿渣对水泥水化有促进作用,自加水开始即表现出一定的火山灰效应。粉煤灰与矿渣掺入后有助于水泥水化产物中钙矾石的稳定,钙矾石抑制了水泥水化,Ca(OH)2生成量减少,因而粉煤灰与矿渣的火山灰反应也受到影响。

In order to evaluate the pozzolanic reaction heat of fly ash （FA） and ground granulated blastfumace slag （GGBS） in temperature simulation of mass concrete, the influence of replacement of FA and GGBS on the hydration process and heat rate of cement was investigated via microcalorimetry, and the behaviors of pozzolanic reaction heat of FA and GGBS before 3 d were analyzed. Reaction heat of FA and GGBS at early age was discussed by X-ray diffraction and differential scanning calorimetry-thermogravimetry （DSC-TG）, respectively. The mechanism of pozzolanic. The results show that the pozzolanic reaction heat of FA and GGBS is 3-5 J/g and 15-16 J/g. The FA has a negative effect on the cement hydration before 24 h, but its pozzolanic effect plays a positive effect on the cement hydration after 24 h. The pozzolanic effect of the GGBS accelerates the cement hydration at early age. Ettringite is more steady in the cement hydration production when FA or GGBS is added, which delays the hydration of cement and produce of Ca（OH）2 Therefore, the pozzolanic reaction of the FA and GGBS can be affected.