Speaker:
Dr. Maciej Zajac, Heidelberg Materials AG, Leimen, Germany

Abstract:                                                                
Recycling of construction materials is crucial for sustainable development. It helps to reduce the environmental impact of construction activities, conserves natural resources, decreases waste generation and reduces CO₂ emissions.

This contribution focuses on carbonation technologies that can be used to valorise industrial streams of cement-based materials while enabling circular economy and CO₂ sequestration. Different approaches and technologies for cement carbonation will be discussed, along with the associated reaction mechanisms for the relevant phase assemblages. The reactivity and application of the carbonated materials as pozzolanic additive for cement and concrete production will also be addressed.

Recent research has shown that carbonation of different industrial material streams can be conducted at ambient temperature and pressure, achieving high degrees of reaction compared to the current level of carbonation of natural magnesium silicate rocks. CO₂ mineralization occurs when calcium reacts with carbonate ions in an exothermic process, resulting in the formation of calcium carbonate and reactive siliceous gel. The carbonated materials can be used as supplementary cementitious materials, contributing actively to the performance evolution. When combined with recycling approaches, carbonation can make a significant contribution to circularity in the building material industry and reduce the CO₂ footprint of cementitious materials.