The durability of recycled aggregates and recycled aggregate concrete

The physical and mechanical properties of two recycled aggregates, crushed concrete and clean, graded mixed debris, have been examined and compared with results obtained for a natural river gravel . Initial characterisation tests were performed on both the recycled and natural aggregates to determine their particle size distribution and particle shape, apparent relative density, water absorption and 10% fines value. Tests were then performed to compare t he workability, compressive strength, modulus of elasticity, and resistance to freeze/thaw conditions of concretes made with these aggregates. The results indicate that recycled aggregates have lower strengths and densities than natural aggregates. Despite this the durability of concretes manufactured with these recycled aggregates is similar to that of conventional concretes.