Long-term carbon dioxide sequestration by concretes with supplementary cementitious materials under indoor and outdoor exposure: Assessment as per a standardized model

Abstract

An experimental study was carried out on concretes designed with an ordinary Portland cement (CEM I 52.5 N), blended cements containing 23 wt% fly ash (CEM II/B-V 32.5 R) or 82 wt% ground granulated blast-furnace slag (CEM III/C 32.5 N), and partial substitutions of CEM I with fly ash (30 wt%) or ground granulated blast-furnace slag (30 and 75 wt%). Measurements were carried out on Ø11X22 cm specimens after 10.8 years of exposure, under indoor and outdoor exposure, to determine their carbonation rates and degrees of carbonation. The objective was to compare CO2 uptake calculated with the parameters measured experimentally to that calculated with parameters defined by a standardized model commonly used by construction engineering (EN 16757 model). The comparison showed that the model: (i) underestimates the carbonation rate (up to 61%), (ii) underestimates the degree of carbonation under indoor exposure (up to 49%) and overestimates it under outdoor exposure (up to 78%), and (iii) considerably underestimates the maximum theoretical CO2 uptake (up to 77%) for high ground granulated blast-furnace slag content. Consequently, the model underestimates the CO2 uptake under indoor exposure (up to 86%). However, the comparison showed a better correlation under outdoor exposure. Based on these results, some adjustments to the parameters defined by the standardized model were suggested to better account for effects of exposure conditions and supplementary cementitious materials, which should improve the CO2 uptake assessment.