Characterization of Hydration Products’ Formation and Strength Development in Cement-Stabilized Kaolinite Using TG and XRD

This study investigates the use of thermogravimetry (TG) and X-ray diffraction (XRD) to characterize and quantify the hydration products, particularly calcium silicate hydrate (CSH) and calcium hydroxide Ca(OH)2, in stabilized soils and to establish correlations between these products and strength gain over time. A pure kaolinite is the soil for this study and portland cement is the selected stabilizer. Untreated and cement-stabilized samples are compacted at their optimum conditions and cured for different periods of up to 90 days. The unconfined compression test, which is a relatively simple and commonly used test, is performed to measure the unconfined compressive strength (UCS) for all the samples and record the macroscopic behavior. A portion of soil from each set of samples is recovered and subsequently subjected to the TG test coupled with mass spectrometry (MS) and XRD. Using TG, the amounts of CSH (mass loss between 105 and 440°C) and calcium hydroxide (mass loss between 440 and 580°C) are measured and monitored with time to establish their correlation with strength gain. Quantitative XRD using whole-pattern fitting (Rietveld analysis) and the reference intensity ratio (RIR) indicated that the amount of kaolinite decreases logarithmically with curing time and a strong linear correlation is observed between the amount of kaolinite and the unconfined compression strength.