地热环境下AFt和AFm的转化机制  

Transformation Mechanism of AFt and AFm in Geothermal Environment

作　　者：任鹏程 郑和平 金祖权[2] 李梦圆 李金鑫 逄博 REN Pengcheng;ZHENG Heping;JIN Zuquan;LI Mengyuan;LI Jinxin;PANG Bo(Lanshan Management Office,Shandong High Speed Rail Transit Group,Rizhao 276800,China;School of Civil Engineering,Qingdao University of Technology,Qingdao 266033,China)

机构地区：[1]山东高速轨道交通集团岚山管理处,日照276800 [2]青岛理工大学土木工程学院,青岛266033

出　　处：《硅酸盐通报》2023年第5期1551-1560,共10页Bulletin of the Chinese Ceramic Society

基　　金：国家自然科学基金(52078259,5191102012,52208259);山东省泰山学者工程专项经费(ts20190942)。

摘　　要：在地热环境下水泥水化初期,单硫型硫铝酸盐(AFm)易与硫酸根在孔隙或界面处生成延迟钙矾石(DEF),导致混凝土膨胀开裂。本文采用溶液法模拟钙矾石(AFt)生成的温湿耦合液相环境,通过分子动力学模拟方法研究AFt在常温和地热环境下的内部结构变化,确定DEF的生成温度界限和水泥中石膏临界掺量。结果表明,地热高温环境会影响AFt晶体在(100)、(110)晶面上的生长,导致AFt生成量随温度升高逐渐减少;70~75℃为AFt转变为AFm的关键温度区间,但在75℃以上液相环境中AFt依然能够生成,转化的AFm含量会随温度增加而逐渐增多;高温对水泥早期水化生成AFt具有促进作用,但随着养护龄期增长,高温会造成早期生成的AFt逐渐转化为AFm;混凝土中AFt生成量随石膏掺量增大而增加,质量分数为4%左右的石膏是适宜掺量;分子动力学模拟结果同样表明AFt在常温下结构稳定,而在地热条件下结构发生改变。At the initial stage of cement hydration under geothermal environment,the monosulfoaluminate(AFm)and sulfate are easy to form delayed ettringite(DEF)in the pores or interfaces,which will lead to expansion and cracking of concrete.The solution method was used to simulate the temperature humidity coupled liquid environment of ettringite(AFt)formation,the molecular dynamics simulation method was used to study the internal structure change of AFt under normal temperature and geothermal environment,and the formation temperature limit of DEF and the critical gypsum content in cement were determined.The results show that the geothermal high temperature environment will affect the growth of AFt crystals on(100)and(110)crystal planes,leading to the gradual decrease of AFt formation with the increase of temperature.70~75℃is the key temperature range for the transformation of AFt to AFm,but AFt can still be formed in the liquid phase environment above 75℃,and transformed AFm content will gradually increase with the increase of temperature.High temperature can promote the formation of AFt hydrated at early stage of cement.With the increase of curing age,high temperature will cause that AFt generated at early stage to gradually transform into AFm.Forming amout of AFt in concrete increases with the increase of gypsum content,and gypsum with a mass fraction of about 4%is the appropriate content.The molecular dynamics simulation results also show that AFt structure is stable at room temperature,but its structure changes under geothermal conditions.

关 键 词：地热环境 延迟钙矾石 临界温度 石膏掺量 分子动力学模拟 结构转变 

分 类 号：TU528[建筑科学—建筑技术科学]