Investigation into the rate of natural carbonation of concrete blocks under Irish production yard conditions

Abstract

The release of CO2 from calcination during the manufacture of cement can be partially offset by the CO2 it naturally absorbs during its lifetime. This paper reports results from a preliminary investigation into the rate of carbonation in concrete blocks stacked in a production yard over a period of 6 months. The blocks were organised in a normal manner under natural exposure conditions. Carbonation progress was determined using phenolphthalein. It was found that the rate of the carbonation front progression differed depending on the exposure face and block type. Carbonation fronts on exposed front (FF) or side faces (SF) were seen to advance at rates of over 1 mm/week for the initial 6 months of exposure. Exposed top faces (TF) showed a slower rate of carbonation of just over 0.6 mm/week. The speed of the advance of the carbonation front into concrete slowed over time, however, it was noted that slower progression occurred during the second half of testing over the winter period. Rates of carbonation and estimates of carbon sequestration were calculated. The findings suggest that carbonation should be included in the manufacturing stage of life cycle assessments for open textured concrete products such as blocks.