Closing Letter of RILEM TC 281-CCC: Carbonation of Concrete with Supplementary Cementitious Materials

The RILEM Technical Committee (TC) 281-CCC, on carbonation of concrete with supplementary cementitious materials (SCMs) was active from 2018 to 2024, bringing together over 120 members from different continents. The objective of the TC was to understand the mechanisms leading to carbonation and identify best practices for the assessment of carbonation resistance of blended cement concrete. The activities of the committee were carried out in five different working groups (WGs) centring on (i) effect of SCMs on natural and accelerated carbonation of blended cementitious materials, (ii) modelling of carbonation, (iii) effects of the combined action of load and carbonation, (iv) carbonation induced corrosion, and (v) carbonation of alkali-activated materials. These topics covered all critical aspects to reveal the connections between the mechanisms and factors leading to carbonation of binders and concrete with SCMs, the impact of carbonation in concrete performance and corrosion, and the suitability of existing testing methodologies for its evaluation. The scientific activities of the TC members led to the publication of a topical collection with nine articles in Materials and Structures and one article in RILEM Technical Letters. This included three critical review papers, six original research papers and one recommendation. In this Letter we provide an overview of the key findings linked to the WGs activities and present remaining research needs on the topic of carbonation of concrete with SCMs.