To assure the quality and required workability of mortar or concrete, various types of superplasticizers are used. There are many factors affecting the performance of superplasticizers explicitly, type and dosage of the superplasticizers, type of cement, temperature and mixing procedure, as well as the addition times of the superplasticizers. Some researchers investigated the effect of delaying the addition time of superplasticizer to mortar or concrete, but there is not enough data about the effect of external temperature on performance of superplasticizers and consequent influences on fresh properties of mortar or concrete. In this research the effect of delaying the addition time of superplasticizers and influence of external temperature, namely, heat stimulation of superplasticizers, on fluidity, fresh density and air content of fresh cement mortar was investigated. Two types of Precast and Ready-Mix of Polycarboxylic acid-based ether superplasticizers with Ordinary Portland Cement was used. Delaying the addition time of superplasticizers enhanced the fluidity, slightly decreased the fresh density and increased the air content of mortar in comparison with simultaneous addition time with both heated and non-heated Superplasticizers.

Abstract-The objective of this research is to study the effects of thermal stimulation of PC ether high performance water-reducing agent on the workability of fresh cement-mortar. For better understanding of the behavior of these admixtures under thermal stimulation condition, two types of water-reducing agents are used, superplasticizer and high range water reducer (Air Entraining type). The chosen admixtures were heated by different temperatures, 40, 50 and 60℃ for two various times, 30 minutes and 24 hours. These conditions experimentally investigated different types of cements, high early strength cement and ordinary Portland cement. As a result, influence of thermal stimulation of admixtures on the workability of fresh cement-mortar is observed. Accordingly, in a specific water cement ratio in cement concrete, the amount of the admixture can be significantly reduced by using thermal simulation technique in comparison to non-thermal stimulated ones. Therefore, it is possible to reduce the economic aspect of production with this technique.Index Terms-Thermal stimulation, superplasticizer, workability, high-performance AE water reducing agent, high range water reducer, fresh properties, mortar paste.

The objective of this study was to investigate the interaction of different types of cement and superplasticizer admixtures in which the Superplasticizers were stimulated by heating before addition to the mortar. To evaluate the desired impacts, tests on the luidity and low loss of mortar were conducted. For better considering the behavior of admixtures under heat stimulation with different cements, three types of cement and two types of superplasticizer are used, Polycarboxylic acid-based and Polycarboxylic acid-based ether. The admixtures were heated to 40˚C, 50˚C, and 60˚C for 0.5 hours and 24 hours. Generally Polycarboxylic acid-based admixtures showed higher low improvement in 60˚C heating with all cement types especially with High Early Cement, in comparison with Polycarboxylic acid-based ether type. The low loss of mortar was reduced by heat stimulation of admixtures, Polycarboxylic acid-based ether (the product suitable for Ready Mix Concrete) showed signi icant low improvement after 15 minutes and kept it to one hour. As the result of this research, it is possible to reduce the admixture dosage and maintain the desired luidity of mortar, or increase the mortar luidity by applying the heat stimulation technique.