3.2.3. TG/DSC characterizationThe T

3.2.3. TG/DSC characterization
The TG/DSC curves of CSK, CSK-K2, CSK-K3 and CSK-K4 are exhibited in Fig. 6, which can provide information about the thermal behavior of samples. The TG curve of CSK (Fig. 6a) shows a mass loss of 10.93% corresponding to the dehydroxylation of CSK (Ruiz-Cruz and Franco, 2000). Meanwhile, a maximum endothermic peak at 533 °C and an exothermic peak at 986 °C were discovered in its DSC curve, due to the dehydroxylation of CSK and the phase transition that forms the mullite (Orzechowski et al., 2006). For the TG/DSC curves of CSK-K3 (Fig. 6c), the maximum endothermic peak occurs at 358 °C owing to the dehydroxylation of CSK-K3, and a mass loss of 15.13% arises between 300 °C and 650 °C, as a result of the decomposition of KAc, the dehydroxylation of CSK-K3, and the dehydroxylation of nonintercalated kaolinite (Cheng et al., 2010). The result discloses that the temperature of dehydroxylation for CSK-K3 decreases dramatically when compared with that of CSK. However, the temperature of dehydroxylation for CSK-K2 expresses no significant decreases as the maximum endothermic peak appears at 512 °C with a mass loss of 12.63% (Fig. 6b). Thus, calcination at 400 °C is not sufficient for the dehydroxylation of CSK-K2, which leads to poor compressive strength of the geopolymer. Moreover, the temperature of dehydroxylation for CSK-K4 emerges at 350 °C (Fig. 6d), which is the lowest of all and the corresponding mass loss is 17.25%. It intimates that a higher dosage of KAc leads to a lower temperature of dehydroxylation. However, considering the result of compressive strength test, too much KAc decreases the compressive strength of geopolymer though the temperature of dehydroxylation is lower. Therefore, the results demonstrate that the KAc intercalated can decrease the temperature of dehydroxylation, but not having more KAc is better.