Supplementary cementitious materials based on recycled concrete paste

The use of recycled concrete not only reduces the consumption of natural materials, but the finest fraction produced also offers a potential to save CO2 emissions. Three novel valorization methods to convert this finest fraction into supplementary cementitious materials were applied to industrially produced fines and assessed regarding their performance, impact on embodied CO2 emissions and energy. The methods - carbonation with and without autoclaving step or production of reactive glasses - resulted in a reduction of embodied CO2 per strength achieved by the composite cements in the range of 10-40% at 28 days. Among the valorization techniques, various methods involving carbonation that actively remove CO2 from the production process were found to be generally more effective also when considering future decarbonation of clinker and electricity production. With the proven feasibility of efficient and value-added valorization of the fine fraction from concrete recycling, the complete concrete recycling can be upscaled and industrially deployed and therefore contribute to make concrete truly circular and carbon-neutral in the future.