Comportamento sob altas temperaturas de concretos com agregados reciclados de concreto

Abstract

Recycled aggregate of concrete (RAC) presents different characteristics from the natural aggregates because it is formed by part of natural aggregate with attached mortar around. This difference directly affects its properties and consequently the concretes produced with. Thus, for the rational use of the RAC in the concrete production, it is necessary to know the relation between the amount of the attached mortar and the rheological, physical, mechanical and durability properties of the concrete. It is interesting to mention that there are not fully studies about the behavior of these concretes under high temperatures. The present work aims to evaluate the influence of recycled aggregates on the physical, mechanical and microstructural behavior of different classes of concrete (C25 e C65), after exposure to temperatures of 150, 400 and 650°C. The concretes were designed using the compressive packing method and the substitution contents, by volume, of coarse natural aggregates by RAC were about 50 and 100%, in order to access the influence of the stuck mortar on the residual properties of the concrete. The results showed that the concretes containing RAC presented practically the same mechanical behavior with the conventional concrete. Until 150°C, the properties of the concretes rose, and a higher degradation started only at 400°C. Microstrutural analyses showed a gradual increase of cracks in the interfaces aggregateold mortar, aggregate-new mortar and new mortar – old mortar, from this temperature.