Avaliação dos parâmetros de durabilidade frente ao ataque por íons cloreto em concreto autoadensável com uso de agregados reciclados de resíduos da construção civil

Abstract

As economic growth drives the accelerated pace of construction, a global environmental crisis is projected as a result of the waste of natural resources from non-renewable sources, thus arousing the search for alternatives for reuse of construction waste (RCW). In this study, the influence of incorporating recycled aggregates of RCW, sand and gravel, on the durability parameters in mixtures of self-compacting concrete (SCC), with and without the addition of metakaolin, submitted to two exposure conditions: in open air and in chloride ion attack cycles, was verified. Five mixtures were produced: (1) reference SCC, with natural sand and gravel; (2) SCC with recycled sand and gravel; (3) SCC with recycled sand and gravel and addition of 10% MK; (4) SCC with recycled sand, natural gravel and addition of 10% MK and (5) SCC with natural sand, recycled gravel and addition of 10% MK. The water/binder ratio was kept constant for all mixtures and the additive dosage was adjusted according to the variation in the use of aggregates. The evaluation of mechanical properties and durability was performed from tests of axial compressive strength, ultrasonic pulse velocity, chloride penetration, chloride ion diffusion and electrical resistivity. The results showed the feasibility of using recycled aggregates in SCC. The addition of metakaolin improved the performance of SCC with the use of these aggregates significantly. The mixture of SCC with recycled sand and metakaolin stood out positively in relation to the others and, therefore, it was concluded that it is possible to produce such a mixture with acceptable performance and ensure a good behavior under aggressive environmental conditions.