Avaliação da autocicatrização de concretos microfissurados com aditivo cristalizante e submetidos a ambiente agressivo

Abstract

This work aims to evaluate the contribution of a national crystallizing additive (CA) in the property of self-cication of structural concretes subjected to damage in the early ages (microcracks) against the mechanical properties of axial compression (Fc)pull in bending (ft), and armor corrosion (CAIM test). Two traits were produced, one of reference and another with the incorporation of 1% of crystallizing additive and both dosed to achieve structural strength of 30MPa. For the tests of the mechanical properties two types of specimens were produced: cylindrical (Fc) and prismatic (ft). For the reinforcement corrosion tests (CAIM), a CA-50 steel bar was inserted in part of the prismatic specimens. After production, the concretes were subjected to submerged curing. At the age of 7 days, three prismatic samples were ruptured at flexion. From the mean rupture value was determined the percentage of 50% of this resistance. At this same age, part of the prismatic specimens were submitted to a pre-loading by tensile flexion of 50%fcm for the induction of damage (microcracks). Part of the prismatic samples remained intact, to serve as a reference. After the imposition of damages, the samples returned to the curing process until the age of 28 days to favor self-cication, when they were tested at flexural tension and accelerated corrosion test (CAIN). The axial compression control test was performed in prismatic samples and not imposed to damage at the age of 14 and 28 days. The results showed that the use of the crystallizing additive increased the axial compressive strength of the concretes, but did not influence the tensile strength in bending, because the reference trait (without AC) showed the best results. In contrast, it is concluded that the preload applied in concretes in the early ages did not imply losses of the evaluated property (flexural tensile strength) for the control age at 28 days. As for the influence of the crystallizing additive on the reinforcement corrosion protection by the CAIM test, it was concluded that the concretes with crystallizing additive promoted a lower loss of mass of the steel bars.