Aditivo cristalizante para concreto: propriedades no estado fresco e endurecido

Abstract

The quality of materials used in reinforced concrete structures could compromise the effectiveness and useful life of the building. The presence of pores in concrete, for example, favors the penetration of agressive agents, and consequently damage steel. Therefore, less permeable concretes have lower risks than the conventional one, when it comes to steel durability. In this sense, the cristalline admixtures can be incorporated into the concrete in order to obtain higher density in the concrete microstructure. The added portion of the additive, however, must be rigorously dosed for better use. This work has as objective the verification of a cristalline admixture regarding the properties in the fresh and hardened state of concrete. Through microscopy there is the classification of concrete and observation of the transition zone which can be improved from the use of additives. Concrete has a useful life that can be reduced by penetrating aggressive agents, which damage the steel and expand its size by up to 8 times. The transport of aggressives can be explained by the principle of capillarity, where the smaller the pore, the greater the water infiltration. Making the microstructure less permeable therefore corroborates for greater durability of reinforced concrete structures. In order to increase the useful life of structures or to recover existing structures, several works in Brazil have already used crystallizing additives. The results of the present study were not able to assess whether the use of cristalline admixture made the concrete less permeable, what is stated is that the properties in the fresh state were not altered with the use of the additive. Resistances to axial compression remained statistically equal when tested over 90 days. There was a significant improvement in absorption by immersion and capillarity when compared from 28 to 210 days, but the control group evolved in the same way.