超缓凝剂对硅酸盐水泥砂浆性能的影响

目的为配制一种新型有机复合超缓凝剂，研究不同掺量及养护条件下其缓凝效果和硬化机理．使之可有效地应用于大体积混凝土及缓黏接预应力混凝土工程中．方法利用XRD和SEM等微观手段，对掺入超缓凝剂水泥砂浆的缓凝性能进行了测试和表征．结果超缓凝剂在不同养护条件下，可使水泥水化“休眠”20～40d，“休眠”结束后能迅速水化而结构不发生变化．XRD图谱表明并未发现异常水化物产生；SEM图像表明，掺超缓凝剂的水泥硬化结构更加致密．结论在标准养护条件下，掺量0．035％的超缓凝剂可使水泥水化“休眠”34d，“休眠”结束后59d可达空白试件28d强度．随养护温度增加和超缓凝剂掺量的降低，水化“休眠”期降低．超缓凝剂并未使水化产物发生本质变化，其耐久性应是可靠的．

The Influence of Super-retarding agent on the Properties of Portland Cement Mortar

A new type of organic composite super-retarding agent has been prepared.In order to apply the super-retarding agent to mass concrete and retarding coherence prestressed concrete construction effectively,the retarding effect and hardening mechanism of the super-retarding agent under different curing conditions and with different additions are studied.The retarding properties of cement paste with the super-retarding agent have been characterized and analyzed by means of XRD and SEM.Under different curing condition,the super-retarding agent can make the cement hydration into "dormant state",the "dormant state" period is from 20 days to 40 days.When the "dormant state" is over,the cement hydration goes on quickly and the microstructure of hydration resultants do not change.The results of XRD show that abnormal hydration resultants do not be found.SEM photographs indicate that the microstructure of hardening cement with super-retarding agent is more compact.Under standard curing condition,0.035% super-retarding agent can make the "dormant state" period of cement hydration lasts for 34 days.After the "dormant state" is over,the 59d compressive strength of cement mortar with super-retarding agent can reach the 28d compressive strength of cement mortar without super-retarding agent.With the curing temperature rising and the addition of super-retarding agent reducing,the "dormant state" period of cement hydration becomes short.The super-retarding agent does not make the cement hydration resultants change essentially,so its durability should be reliable.