Workability and rheology of fresh recycled aggregate concrete

The use of recycled aggregates concrete (RAC) with coarse recycled concrete aggregates (CRCA) has been widely studied in literature. A number of works investigated both mechanical and durability-related properties of these concretes; however, fresh properties of RAC have not been extensively analyzed yet. Limited studies were focused on the influence of some recycled aggregate properties on slump, which is the most frequently used measure to evaluate workability. Since this measure is a single-value and it is often operator-sensitive, a more quantitative estimate can be derived in terms of fundamental physical quantities, such as plastic viscosity and yield stress. The higher heterogeneity in terms of experimental slump measure occurs indeed when recycled aggregate concrete is tested. In this chapter, a review of the existing experimental methods for the evaluation of fresh concrete workability is given. Additionally, the behavior of fresh concrete is explored, aiming to understand which physical phenomena govern the macroscopic rheological behavior, under some specific conditions, e.g. in terms of mix composition, casting conditions, etc. Some experimental results about fresh recycled concretes workability and rheology, collected from literature, are also discussed.