Reuse of recycled crushed concrete fines as mineral addition in cementitious materials

Environmental issues have led European stakeholders to join around an ambitious project, the reuse 70 % of inert wastes from construction and demolition by 2020. Among available solutions, the reuse of fine recycled aggregates as substitute of natural sand is somewhat problematic due to their high water absorption. The aim of the present research is to study a new way of recovery for fine recycled aggregates. We propose to use them as mineral addition, after a process of crushing and sieving resulting in powder (particles diameter lower than 80 lm). For this purpose, Recycled Crushed Concrete Fines (RCCF) were prepared from a 5 years old concrete and characterized by a physico-chemical approach. Attention was paid to assess the content of anhydrous cement. Mortars with different substitution levels of Portland cement by RCCF (Recycled Crushed Concrete Fines) or limestone filler were also studied at both fresh and harden states. The studied RCCF were found to have low content of anhydrous cement and thus low hydraulic properties. However, RCCF (Recycled Crushed Concrete Fines) was found to play a similar role than limestone filler on cement hydration. Portland cement could be substituted by RCCF (Recycled Crushed Concrete Fines) up to 25 % without altering properties of mortars. These results are encouraging and lead us to continue our research with inert wastes from real demolition sites.