Influence of seawater and blast furnace cement employment on recycled aggregate concretes' properties

Recycled aggregates of mixed composition (MRA) may exhibit great variability in their properties, which in turn reduces their applicability. This study intends to extend the use of MRA in a broadened scope of applications by producing recycled aggregate concretes (RAC), which were mixed using two different types of cement, ordinary Portland cement and cement incorporating blast-furnace slag, and two types of water, fresh and seawater. The testing programme included analyses of the properties of concrete in its fresh (setting time and plastic shrinkage) and hardened state (physical, mechanical and drying shrinkage). The results showed that all of the physical and several of the mechanical properties as well as drying shrinkage were negatively influenced by the use of MRA. In contrast, however, the plastic shrinkage and flexural strength were improved. The use of seawater improved the mechanical properties, reduced setting time and increased drying shrinkage, however, it was found that the cement type was more influential on most of the properties. The use of seawater and cement with blast-furnace slag improved the performances of the RAC.