Propriedades mecânicas e durabilidade de concretos produzidos com agregados miúdos reciclados e metacaulim dosados pelo modelo de empacotamento compressível

Abstract

When it comes to construction and demolition waste, the small portion of it is often discarded since this material is capable of producing changes in fresh and hardened properties of concrete as well as modifying durability characteristics. The current Brazilian technical standard indicates that the use of recycled aggregate in structural concrete must be limited to 20% of the total amount of aggregates in mass. Thus, structural concrete of C30 and C50 grade were studied, considering replacement contents of fine natural aggregate by recycled ones varying between 0% and 25%. The concrete mixtures were designed regarding the Compressible Packing Model (CPM), optimizing them for maximum packing density. Slump test, compressive strength test, splitting tensile test, capillarity and total absorption, drying shrinkage and chloride penetration were carried out for all mixtures. The concretes that contained recycled fine aggregates and metakaolin achieved satisfactory mechanical properties when compared to reference concrete. Regarding the durability properties evaluated, concretes with recycled aggregates presented advantageous results when considering capillarity absorption, total absorption and chloride penetration. In relation to drying shrinkage, mixtures with recycled aggregates presented higher shrinkage when compared to reference mixtures. Furthermore, the use of these aggregates with metakaolin produced positive results in terms of durability.