Study on the synergistic retarding effects of the compounding of superplasticizer with retarders

The synergistic retarding effects of retarders compounded with superplasticizers on the initial and final setting time of cement and concrete was investigated.Three types of retarders were sodium gluconate,sodium tripolyhosphate and calcium sugar.Three types of superplastici-zers used were naphthalene-based,ammonia-based and polycarboxylicate-based superplasticizers.The results showed that a appreciable positive synergistic retarding effect could be seen when the retarder used together superplasticizers,for the fixed water-cement ratio;compared to retarders used separately,if superplasticizers used together with retarders,the initial and final setting time of cement and concrete can be further prolonged.The synergistic retarding effect for paste of normal consistency was smaller than that of fixed water-cement ratio.The ammonia-based super-plasticizers displayed retarding property.The synergistic effect of the ammonia-based superplasticizers/retarder combination was even obvious.