The use of carbonation depth techniques on stabilized peat

Abstract

The phenolphthalein indicator method, the pH of slurries method, X-ray powder diffraction analysis (XRD), and Fourier transform infrared spectroscopy (FTIR) are all commonly associated with evaluating the carbonation front depth in concrete. Recent research (using a closed chamber method) has indicated that stabilized peat is a net sink of carbon dioxide (CO2) (at least in the short term), as the binder takes in CO2 both from the atmosphere and any CO2 released by oxidized peat. Therefore, the application of carbonation depth techniques to stabilized peat are of interest and are explored in this paper for the first time as a precursor to developing a greater understanding of the carbonation process in this material. The carbonation fronts obtained by XRD, loss on ignition, and FTIR all arose at similar depths, as these methods all identify the depth at which the calcium carbonate concentration is elevated with respect to the baseline (i.e., the maximum advancement of the carbonation front). In contrast, the phenolphthalein method underestimated the carbonation front considerably. The pH of the stabilized peat slurries method gave the depth at which leaching of calcium hydroxide and calcium ions occurred, rather than a carbonation depth, and exceeds the depths determined from the other techniques. Advantages and disadvantages of all techniques are discussed.