磷石膏基超硫酸盐水泥水化过程中胀缩行为研究

Study on the Behavior of Swelling-Shrinkage in Hydration Process of Phosphogypsum-based Super-Sulfated Cement

磷石膏基超硫酸盐水泥(PSSC)水化时存在体积胀缩行为,这种行为对工程建筑的稳定性是否产生不利影响尚不明确,因此明晰该行为的产生机制至关重要.为探究PSSC的胀缩机制,开展了“恒体积法”膨胀力、体积胀缩量、水化热、X射线衍射(XRD)、扫描电镜(SEM)试验,研究水化热、失水率、各水化产物的含量、水化物的晶体形态对体积胀缩的影响;通过汞孔隙法(MIP)进一步揭示胀缩行为对结构孔隙的影响.结果表明:水化前期,水化温度急剧上升,水化产物中钙矾石呈放射状生长,引起PSSC迅速膨胀;水化中期,PSSC的膨胀速率随着钙矾石生成速率的减缓而降低;水化后期,PSSC体系的持续失水导致其体积略有回缩.MIP结果进一步证明,胀缩行为使得孔隙结构更加密实.

The volume expansion and contraction behavior observed during the hydration of phosphogypsum-based super-sulfate cement(PSSC)remains unclear in terms of its potential adverse effects on the stability of engineering structures.Therefore,it is very important to clarify the mechanisms underlying this behavior.In order to investigate the expansion and shrinkage mechanism of PSSC,the expansion force test which carried out by the"constant volume method",volume expansion and shrinkage test,heat of hydration test,X-ray diffraction(XRD)and scanning electron microscopy(SEM),which revealed the effects of heat of hydration,water loss,content of each hydration product and hydrate crystal morphology on the volume expansion and shrinkage.The effects of volume expansion and contraction on the structural porosity were investigated by mercury intrusion porosimetry(MIP)and SEM.The results show that:the large amount of heat of hydration and the radially growing ettringite in the hydration products caused the rapid expansion of PSSC in the early stage of hydration;the slow generation of ettringite lead to the less expansion of PSSC in the middle stage of hydration;the continuous loss of water in the late stage of hydration led to the shrinkage of the PSSC;and the expansion and shrinkage behaviors resulted in the more compact of the pore structure.