Properties of Concrete with Thermo-mechanically Beneficiated Fine Recycled Aggregates

There is a worldwide shortage of fine aggregates/sand, and recycled concrete aggregates could be an alternate source to meet the demand. However, the main problem associated with the fine recycled concrete aggregate (FRCA) is the high amount of low-density porous adhered cement paste. This, along with the presence of finer particles (<300 mu m), could increase the absorption capacity of FRCA significantly. Considering this in the present study, an attempt has been made to use thermo-mechanical beneficiation, where waste concrete was heated at a temperature of 400-500 degrees C followed by cooling at ambient temperature, after which it is processed further with the help of a ball mill. After this, the finer particles (<300 mu m) are separated to give FRCA that has been used in concrete mixtures of 40 MPa design compressive strength. The mechanical properties were found to be comparable to the reference mix with natural sand. Also, the results from durability tests show that the use of beneficiated FRCA would not significantly reduce the durability of concrete, which could be a major concern.