Carbonation of cement paste: Understanding, challenges, and opportunities

• A systematic review of literature related to mechanisms of carbonation in cement paste is given.
• Active uses of carbonation for improvement of cement based materials are also discussed.
• The study provides a starting point for research of carbonation in new cementitious materials.
• It can be of use for development of new active carbonation procedures which utilize and capture CO2.

Cement paste is known to react with atmospheric carbon dioxide. Carbonation of cement paste has long been recognized as one of the causes of reinforcement corrosion. On the other hand, carbonation causes numerous chemomechanical changes in the cement paste, most notably changes in strength, porosity, pore size distribution, and chemistry. Furthermore, it can cause shrinkage and cracking of the cementitious matrix. The present review summarises the state of the art regarding the understanding and consequences of carbonation of cement paste. Apart from the passive process of reaction of atmospheric CO2 with cement paste, carbonation is sometimes used on purpose in order to improve certain properties of cementitious materials. This review further summarises recent efforts regarding active use of carbonation as a tool for manipulating certain properties of cement based materials. Possible fields of application include accelerated curing, improvement of fibre reinforced cementitious composites, concrete recycling, and waste immobilization.