Accelerated carbonation effect on behaviour of ternary Portland cements

The carbonation of hydrated ternary Portland cement (TPC), containing thermally activated paper sludge and fly ash, was studied in a semi-dynamic atmosphere of 100% CO2, and 65% relative humidity at 20 ± 1 °C, for a period of 30 days. The changes of the mineralogical phases and porosity before and during the carbonation were characterized by X-ray diffraction and mercury intrusion porosimetry. The kinetics of the process was evaluated from the total CaCO3 content by means of thermogravimetric analysis. The pH of the simulated pore solution was analyzed before and after different periods of time. An equivalent study was carried out on ordinary Portland cement (OPC), whose results were compared to those of TPC one. The carbonation attack was 2.2 times faster in the case of the TPC. The results were discussed on the basis of the different porosity, portlandite content and pH of the pore-solution.