8 Pages

Chemical changes and carbonation profiles of carbonated cement pastes at 80°C for different relative humidities

E. Drouet, S. Poyet & P. Le Bescop J.M. Torrenti

ABSTRACT: In the framework of radioactive waste management in France, the concrete structures would be submitted to heating due to the waste thermal output (80°C) and subsequent drying. Such environmental conditions are expected to modify the carbonation mechanisms. The objective of this work is then to evaluate the impact of RH and temperature on carbonation using a device especially developed to perform accelerated tests under temperature. Four hardened cement pastes are tested (w/c = 0.40): European CEM I, CEM II, CEM V and Low pH mix. The carbonated depth and the mineralogical modifications induced by carbonation are assessed using XRD and TGA. The results obtained at 80°C show the formation of aragonite and vaterite, as well as calcite and the reduction of katoite and C-S-H amounts. The relative proportions of aragonite and vaterite appear to be influenced by the water content. A systematic more important carbonation depth for the blended cements is shown.