Valorisation of fines recycled concrete obtained by mechanosynthesis for construction materials production

Deconstruction concretes are reused as aggregate or fill. Most of these materials are recovered as new concrete aggregate or granular pavement materials, particularly in structural layers such as pavement bases and sub-bases. However, the finer parts of the concrete are relatively unexplored despite their high hydraulic and pozzolanic potential. Fine recycled concrete (FRC) obtained by mechanosynthesis is studied as cement substitution, different milling times (5, 15, 30 and 60 min), and rotation speed (200 and 400 rpm) carried out. X-ray diffraction analysis showed that mechanical activation resulted in the portlandite amorphisation and nanocrystalline quartz and calcite formation. Furthermore, the use of 50% of activated FRC as a CEMI substitution for mortar confection resulted in an improvement of compressive strength compared to the use of the unmilled FRC estimated at + 110%, +61% and 68% at 1,7 and 28 curing days, respectively. However, compared to a 100% CEMI mortar, the performances are lower but reach CEM II and CEM III mechanical performance.