TY - JOUR A1 - Vanoutrive, Hanne A1 - Alderete, Natalia A1 - De Belie, Nele A1 - Etxeberria, Miren A1 - Grengg, Cyrill A1 - Ignjatović, Ivan A1 - Ling, Tung-Chai A1 - Liu, Zhiyuan A1 - Garcia-Lodeiro, Inés A1 - Medina Martínez, César A1 - Sanchez, Javier A1 - Palomo, Angel A1 - Rebolledo, Nuria A1 - Sakoparnig, Marlene A1 - Sideris, Kosmas A1 - Thiel, Charlotte A1 - Van den Heede, Philip A1 - Vollpracht, Anya A1 - von Greve-Dierfeld, Stefanie A1 - Wei, Jinxin A1 - Zając, Maciej A1 - Gruyaert, Elke T1 - Report of RILEM TC 281-CCC: outcomes of a round robin on the resistance to natural carbonation of Portland, Portland-fly ash and blast-furnace cements and its relation to accelerated carbonation JF - Materials and Structures N2 - Numerous (inter)national standards are in place for assessing the resistance to carbonation of mortar and concrete. Within the framework of RILEM TC 281-CCC ‘Carbonation of Concrete with SCMs,’ an extensive interlaboratory test campaign (ILT) involving twenty-two participating laboratories worldwide was initiated to compare natural carbonation of concrete and mortar with three different cement types (Portland cement (CEM I), Portland-fly ash cement (CEM II/B-V) and blast-furnace cement (CEM III/B)) and investigate its relation to accelerated carbonation as reported in Vanoutrive et al. (Mater Struct 55:1–29, 2022). It could be concluded that ranking of cement types was analogous between accelerated and natural carbonation methods. Environmental parameters have an important effect on the carbonation rate, however, differences between the mean carbonation rates originating from indoor and sheltered outdoor natural exposure with different exposure conditions and curing regimes were insignificant for each considered cement type. This is caused by the scatter related to carbonation testing among different laboratories. Nevertheless, results showed that a natural exposure period of at least one year is essential to reach a constant carbonation rate over time. For both natural and accelerated carbonation, the carbonation rate increased by 18% when the aggregate-to-cement ratio increased by 1.79 (concrete versus mortar). This correlation seems insensitive to binder type and exposure method. Finally, the best correlation between natural and accelerated carbonation was found for EN 12390–10 (specifically natural indoor exposure) and EN 12390–12 (accelerated exposure) when only test methods performed by more than one laboratory were considered. Y1 - 2024 U6 - https://doi.org/10.1617/s11527-024-02464-1 SN - 1359-5997 VL - 57 IS - 9 PB - Springer Science and Business Media ER -