The influence of relative humidity on structural and chemical changes during carbonation of hydraulic lime

Reference:

El-Turki, A., Ball, R. J. and Allen, G. C., 2007. The influence of relative humidity on structural and chemical changes during carbonation of hydraulic lime. Cement and Concrete Research, 37 (8), pp. 1233-1240.

Related documents:

Official URL:

http://dx.doi.org/10.1016/j.cemconres.2007.05.002

Abstract

Studies monitoring the carbonation of NHL3.5 hydraulic lime are described. Weight-gain measurements, focused ion beam imaging, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy were used to monitor changes in structure and composition occurring in lime pastes after exposure to 100% carbon dioxide at relative humidities of 65 and 97%. Lime paste exposed to a relative humidity (R.H.) of 97% indicated a higher carbonation rate compared to paste exposed to 65% R.H. Surface analysis showed that the sample exposed to a relative humidity of 97% was completely carbonated. No calcium hydroxide was detected. A small amount of calcium hydroxide was, however, present at the surface of the sample exposed to 65% R.H. These observations suggest that high humidity results in the formation of a thin layer of crystalline calcium carbonate covering silicate and hydroxide phases. The actual mass increase of the sample also indicated that uncarbonated calcium hydroxide remained beneath the surface.

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