CONICET | Buscador de Institutos y Recursos Humanos

Heat development during portland cement hydration is affected by the type of cement used, thepresence of additions and admixtures, "water / binder material" ratio, the calcium sulfate state,temperature, and others. Hydration process can be monitored by calorimetric techniques whichpermits to evaluate from the time that cement comes into contact with water, the paste behaviorthrough the release rate of heat produced by the interpretation of acceleration or delay of hydrationreactions as well as the intensity of the heat release occurring. Fresh concrete temperature plays anessential role in transportation, placing and curing, accelerating or delaying the onset of reactionsand/or modifying the speed of them.Furthermore, the presence of superplasticizer, while achieve significant reductions in water mixingamount, modify the properties of concrete according to the dose and composition of cement. Thiscauses changes in the time of placement, curing, strength development, among others.In this paper the influence of one water-reducing admixture in two cements with low and high C3Acontent, which was previously heated to remove partially and totally the combination water of calciumsulfate, are evaluated. Through a calorimeter, hydration development under isothermal conditions(20 and 30 °C) was studied.Results show that in general increasing the dose of admixture the hydration reactions are delayed, andon the other hand because of the prior heating of cement significant changes are produced in theacceleration of these reactions. With increasing temperature, the hydration reactions occur earlierwith higher intensity peaks.When high C3A cement is used, the preheating does not produce significant changes in the hydrationreactions, but when C3A is low, the result are very different.Finally, the increase in temperature of pastes makes accelerate reactions and heat release intensitiesincrease.