Contribuição ao estudo de aceleração de desenvolvimento de resistência do concreto visando á indústria de pré-fabricados

Abstract

The construction industry has been growing requiring improvements in the performance of materials, procedures and human resources. In order to improve concrete performance in the first ages, strategies have been used, among them the steam cure, the autoclave and the use of accelerators additives. In addition, a plausible alternative has been the heating of the materials, especially the mixing water. It is known that the temperature of the mixing water produces significant changes in the rate of hydration of the cement solids in influencing the properties of the fresh and hardened concrete. In precast industry to increase productivity it is necessary to optimize to the maximum the use of forms. However, in the southwest of Paraná, more specifically in Pato Branco, have been periods when the daily average temperature is 8° C, which greatly affects the rate of hydration of the cement solids and therefore the deadlines for the release and lifting parts. Consequently, it is noted that it is indispensable to adopt actions to mitigate the effect of temperature on the concrete hydration rate. The actions taken in order to obtain minimum adhesion strength for lifting the pre-molded parts were as follows: consider the cement and the aggregates at 8 ° C temperature and heat the water to 60 ° C kneading employ accelerators and handle hardening and superplasticizers, dose relationships with three different water / cement ratio. Furthermore, to minimize adherence voltage, it is considered that the parts would be raised at four points. Were produced three concrete mix and then after curing were tested compression thereby yielded results that did not satisfy the desired strength. For comparison and trying to solve the problem over 6 traces were produced with the curing time of 24 hours and 7 days, cured at 8 and 22 ° C. The results are that the mixtures cured at 8 ° C with 24 hours does not reach the desired strength. Since cured at 22 ° C, aged 24 hours and 7 days at 8 ° C and 7 days reached the desired strength.