Internal carbonation of calcium silicate cement incorporated with Na2CO3 and NaHCO3

초록

This study investigates internal carbonation in calcium silicate cement (CSC) paste using sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3). CSC slurries, with 2.5-10 % Na2CO3 and NaHCO3 were cured under a 60 degrees C atmosphere along with CSC slurries cured under a 10 % COQ environment. Microstructure and carbonation kinetics were studied using analytical tools such as TGA, XRD, FT-IR and ITC. CSC primarily comprises non-hydraulic phases such as CS, beta-C2S, C3S2 and gamma-C2S, which are depleted with increased Na2CO3 and NaHCO3 content due to the carbonation reaction. This reaction is exothermic and accompanied by a higher heat release than CSC slurries. The inclusion of NaHCO3 in the CSC matrix promotes the formation of strength- giving phases such as CaCO3 and amorphous phases. Moreover, the IR spectra show the consumption of Q0 and Q1 silicate species accompanied by a subsequent increase in carbonate absorption dip during carbonation.

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