The Use of Thermogravimetry in Quantifying the Hydration Products in Cement-Stabilized Kaolinite

The study presented in this paper was aimed at investigating the use of thermogravimetry (TG) to quantify the amounts of various hydration products, particularly calcium silicate hydrate (CSH) and calcium hydroxide (CH), in stabilized soils and establish correlations between them and strength gain over time. For that purpose, a pure kaolinite was chosen as the soil for this study and Portland cement was the selected stabilizer. Kaolinite samples and cement-stabilized samples were compacted at their optimum conditions and cured for different periods of time up to 90 days. The unconfined compression test, which is a relatively simple and commonly used test, was performed to measure the unconfined compressive strength (UCS) for all the samples and record the macroscopic behavior. Then, a portion of soil from each set of samples was recovered and subsequently subjected to the TG test which was performed at a constant heating rate of 10 K/min until 1000 ^oC, while being connected to a mass spectrometer (MS) for simultaneous evolved gas analysis. The thermal decomposition was divided into four major regions i) desorption of adsorbed water below 105 ^oC, ii) dehydration of CSH phases between 105 and 440 ^oC, iii) dehydroxylation of kaolinite and CH between 440 and 580 ^oC, and iv) decarbonation of calcium carbonate at temperature between 580 and 1000 ^oC. The quantitative analysis revealed that strong linear correlations exist between the amounts of CSH and CH, and strength gain.