复合使用高效减水剂与缓凝剂对水泥水化历程的影响

INFLUENCES OF COMBINATION OF SUPERPLASTICIZERS AND RETARDERS ON PROCESS OF CEMENT HYDRATION

用直接测温法及X射线衍射技术,系统研究了萘系、氨基磺酸盐系及聚羧酸盐系3种高效减水剂,三聚磷酸钠及糖钙2种缓凝剂及复合使用高效减水剂与缓凝剂对水泥水化热、水化温峰、温峰出现时间及不同水化龄期Ca(OH)2和钙矾石(ettringaite,AFt)生成量等方面的影响。结果表明:单掺高效减水剂使水化温峰升高,温峰出现时间延迟,水化热及温峰时的Ca(OH)2生成量增加。单掺缓凝剂使水化温峰降低,温峰出现时间大幅度延迟,水化热及温峰时的Ca(OH)2生成量明显减少。复合使用高效减水剂与缓凝剂时,由于协同效应,使高效减水剂的分散作用及缓凝剂的缓凝作用同时得到加强。与单掺缓凝剂相比,复掺后水泥水化温峰出现的时间进一步延迟,水化温峰进一步降低,水化热及水化温峰时Ca(OH)2生成量进一步减少;但是,外加剂对AFt生成量影响不大。

By using the direct thermometry and the X-ray diffraction technique, the influences of superplasticizers, retarders and a combination of superplasticizers and retarders on cement hydration heat, the temperature peak of hydration, the time of the appearance of the temperature peak, and the quantity of Ca（OH）2 and ettringite （AFt） at different ages were investigated. Three types of superplasticizers were used as followings： naphthalene-based, ammonia-based and polycarboxylicate-based superplasticizers. Two types of retarders were used as followings： sodium tripolyphosphate and calcium sugar. The results show that the three superplasticizers can raise the height of the main temperature peak of hydration, postpone the temperature peak, and increase the hydration heat and the quantity of Ca（OH）2 at the time of the appearance of the temperature peak. The retarders used can lower the height of the main temperature peak of hydration, obviously postpone the temperature peak, and decrease the hydration heat and the quantity of Ca（OH）2 at the time of the appearance of a temperature peak. Compared with the situation of retarders used separately, if the superplasticizers are used together with the retarders, both the dispersing action of the superplasticizers and the retarding action of the retarders can be strengthened due to their interaction, so the temperature peak of hydration can be further postponed, the temperature peak can be further lowered, and the hydration heat and the quantity of Ca（OH）2 at the time of the appearance of a temperature peak can also be further decreased. However, chemical admixtures slightly affect the quantity of ettringite.