Avaliação da eficiência de sistemas de reparo no combate à iniciação e à propagação da corrosão do aço induzida por cloretos

Abstract

The present work evaluated the efficiency of five systems of repair to minimize the initiation and propagation of corrosion rebars attacked by chlorides ions. These systems consist in 5 types of mortars with a w/c ratio of 0,50 and cement:sand proportion of 1:3 and one with iron bars covered with a zinc primer. The attack evaluation was made by accelerated corrosion experiments in cycles of humidity and drying of prisms samples (45x80x90cm). These samples had two 5 mm diameter ion bars inside that were 5 and 10 mm far from the border. The accomplished rehearsals were modulus of elasticity (NBR 8522, 1984) and compressive strength (NBR 5739, 1993). Some durability experiments were also carried out: immersion absorption (NBR 9778, 1987), capillary absorption (NBR 9779, 1995), chlorides diffusion and determination of chlorides content in mortars. At the end, it was made an economic analysis of each system. The mortar samples used to measure mechanical and durability properties were cured in an humid camera during 7 days and later on in laboratory atmosphere until to complete 28 days. The results achieved point out a considerable increasing in compressive strength and modulus of elasticity of the mortar with addition of silica fume. The addition of estirene-butadiene (SBR) didn't modify the compressive strength of the mortar significantly, although it has turned it more deformable. Also, the sodium nitrite did not check significant modifications in these properties. In the durability point of view, the system of repair modified of estirene-butadiene polymer (SBR) showed the best performance, followed in a decreasing way by silica fume, sodium nitrite and zinc primer. The economic analysis indicate that the silica fume system of repair is the best one.