Influência do teor de metacaulinita na avaliação da aderência de compósitos cimentícios reforçados com fibras, como reparo de estruturas de concreto

Abstract

The deterioration of concrete structures is a recurring problem that requires good quality repair interventions. Good adhesion at the repair-concrete interface is essential when applying repairs. However, this adhesion depends on the physical-chemical and mechanical properties of the materials, in addition to the roughness of the concrete surface. This work addresses an experimental program that seeks to evaluate the adhesion between a concrete substrate and cementitious composites reinforced with fibers with different contents of metakaolin, used as a cementitious addition. Four mixtures of fiber-reinforced cementitious composites were tested. The different mixtures were characterized through physical and mechanical tests. To study the adhesion between concrete and cementitious composites, prismatic and cylindrical composite specimens (concrete/repair) were manufactured. Two types of adhesion tests were carried out on the repaired assembly, the slant shear and the diametral compression tensile tests. In the diametral compression tensile tests, 3 types of roughness were used and in the slant shear tests, only one roughness was used. Furthermore, in the slant shear tests, three different angles (20º, 25º and 30º) of the inclined concrete-composite adhesion surface were used. The substrate used was conventional concrete and fresh repair materials were applied over the hardened concrete. After 28 days of repair molding, the repaired sets were tested. When characterizing the mixtures used as repair material, it was observed that the mixtures with the presence of metakaolinite obtained compressive strength and elastic modulus similar to the mixture without metakaolinite at 28 days. Regarding flexural strength, a decrease was observed with increasing metakaolinite content, while deflection capacity increased. After analyzing the adhesion results, it can be observed that the higher metakaolinite content provided better performance in relation to adhesion strength, obtained in the different tests, and the cohesion between the concrete and the composite.