Valorization of mineral waste through accelerated carbonation

Mineral waste is by far the largest waste stream in Europe. Unlike other waste streams, it is rarely recycled and is predominantly disposed of in landfills. The aim of this study is to bring added value to some mineral waste by valorizing them as a partial substitute for cement in mortar composition.

To this end, mineral wastes are first crushed to obtain particle sizes ranging from 0 to 100 μm. Half of the resulting fine particles undergoes a carbonation process. Tests are carried out on fresh mortars in which cement is partially replaced by carbonated or non-carbonated fines, to evaluate their impact on mortars workability. Initial findings indicate that, at a fixed substitution rate, carbonation of the studied fines improves the workability of the mortars by reducing their porosity.

Tests are also conducted on hardened mortar specimens to determine their mechanical strength. Preliminary tests indicate that carbonation treatment of fines contributes to improve the mechanical performances of mortar specimens compared to specimens made of raw fines, although both result in a loss of mechanical properties when substituted to Portland cement. It also helps to reduce the porosity of the hardened mortar and, consequently, improves its durability.

In conclusion, substituting cement with carbonated fines slightly improves the durability of mortars, and reduces the loss of mechanical strength compared to mortars made with non-carbonated fines. Workability is also improved when fines are carbonated.