Development of More Accurate Methods for Determining Carbonation Depth in Cement-Based Materials

Kai Zhang,Marcus Yio,Hong Wong,Nick Buenfeld

Cement and Concrete Research（2024）SCI 1区

Imperial Coll London

Cited 12|Views12

Abstract

Measuring carbonation is increasingly important, especially for developing novel low-CO2 cements and carbon capture technologies. This study shows for the first time, the feasibility and advantages of confocal Raman microscopy (CRM) for measuring carbonation depth in cement-based materials, providing high spatial resolution (down to <100 mu m), by mapping CaCO3 and Ca(OH)(2). Pastes and mortars of different binders (CEM I, 30 % PFA, 50 % GGBS) and w/b ratios (0.45, 0.60) exposed to natural (440 ppm CO2) and accelerated carbonation (4 % CO2) at 65 % RH, 21 C for up to 3 months were tested. CRM shows a sharp carbonation front, without the transition zone commonly supposed. Carbonation depths measured with image analysis of CRM-CaCO3 maps and phenolphthalein-treated surfaces are in excellent agreement, however the latter is less reliable for depths <5 mm. Profile-based methods (TGA, XRD, FTIR, RS and BSE) systematically over-estimate carbonation depth; a simple method to correct this error is proposed.

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Key words

Carbonation,Ca(OH)2,CaCO3,Confocal Raman microscopy,Durability,Image analysis,Microstructure

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