A critical review of the resulting effective water-to-cement ratio of fine recycled aggregate concrete

Abstract

The initial moisture condition of recycled concrete aggregates has a great influence on the fresh and hardened state of concrete. Water compensation is generally proposed with the aim of avoiding changes in the effective water-to-cement ratio and preventing water transfer from the mix to the porous aggregates. However, full compensation of water absorption of aggregates is not recommended. The issue remains unclear for recycled aggregates in general, and for fine recycled concrete aggregates (FRCA) in particular. Moreover, the water absorption of FRCA shows large variations depending on the determination method, making the value for the effective water-to-cement ratio even more uncertain. This paper entails a revision on the knowledge of the FRCA absorption kinetics and its consideration in mix proportioning. Own experimental results and data from the literature are analysed to show the relationship between the compressive strength of concrete and both the effective and total water-to-cement ratios. Compressive strength seems to be notably affected by how FRCA water absorption is taken into account in mix proportioning.