Durability of Recycled Aggregate Concrete Under Real Conditions in Tropical Ambience

Abstract

The substitution of natural resources by the use of recycled aggregates from construction and demolition waste is a huge advantage for the sustainability in the concrete production. The presented paper considers different processing methods of recycling material evaluated with respect to their advantages and disadvantages in sustainability. But once the recycled aggregates are used in concrete, there is a lag of knowledge in the field of its durability behavior. Durability results from a long-time study on 100% recycled aggregate concretes (RAC) suspended the real conditions in a tropical island are presented with respect to their chloride ingress. As reference a natural aggregate concrete (NAC) with the same w/c-ratio was used. The compressive strength of the RAC reached 30 MPa and is only 6% less than that for natural concrete. Samples of each concrete are exposed to three sites of different aggressiveness depending on the distance to the sea, which involves for one site wet-dry cycles by tides or changes in the relative humidity and the chloride content of the ambience. After 5 month exposure the chloride ingress of samples exposed to the sea shore is up to 39% lower in RAC than in NAC. The changes of chloride ingress with time are observed with a second measurement after 17 month exposure. Results in the carbonation show similar trends in the durability behavior with a lower carbonation depth in RAC. However, remaining tests such as electrical resistance and air permeability show better results for NAC.