Workability study of concretes made with recycled mortar aggregate

The use of recycled aggregates (RA) for concrete production usually involves a reduction of the workability as measured by slump. This reduction is mainly due to higher absorption rates, rough-textured surfaces and particles with quite irregular shape from RA. Besides that, the slump test is a static test, whose result is influenced by its own weight and by internal friction between particles. Because of that, recycled concrete workability is not well explained by the slump test. Thus, the main goal of this study is to assess the workability of concrete by varying: (1) workability tests (slump test, flow test and VeBe test); (2) the amount of fine and coarse RAs (0, 50 and 100 %); and, (3) the compensation index of RA absorption rates (60, 70, 80 and 90 %). Concrete compressive strength, at 28 days of age was also evaluated. It was observed that the flow test is the most suitable method for measuring the workability of recycled concrete. The results show that increasing the compensation index of RA absorption rate, there is an improvement of the workability of concrete and a reduction of compressive strength, which is related to the increase of the initial water content in mixtures.