# Internal Curing Effect of Waste Glass Beads on High-Strength Cement Composites
## 3 Results and Discussion
### Tga  
Figure 6 shows the derivative TG/TGA (DTG/TGA) results of HSCC specimens at the ages of 3 and 56 d, respectively. The weight loss at 100 \({}^{\circ}\)C or less was caused by the dehydration and decomposition of bound water and ettringing [43]. At the age of 3 d, SP and R10 specimens showed the highest weight losses, which were 2.53% and 3.69%, respectively. At the age of 56 d, S20 and R10 specimens exhibited the highest weight losses, which were 3.24% and 2.79%, respectively. The weight loss observed in the range of 250-280 \({}^{\circ}\)C is due to the decomposition of aluminum hydroxide [44]. Among S-group specimens at the age of 56 d, S10 and S20 specimens showed thermal decomposition and mass losses of 2.22% and 2.32%, respectively. As WGB content increased, the weight reduction in samples increased, and a more dynamic difference was observed in room temperature curing than in steam curing. According to Figure 7, at the age of 3 d, the SP sample had the highest weight loss. However, according to Figure 8, at the age of 56 d, the S20 sample had the largest weight reduction with a WGB content of 20%. Pre-wetted WGBs reduced the strength owing to the nature of LWAs, but the water contained inside contributed to the hydration reaction in the matrix, as confirmed by the difference in the TGA of the generated hydrates. Figure 6: Quantitative calculation results for clinker constituents and product hydrates calculated from the results of XRD quantitative analysis. Figure 7: Thermogravimetric analysis (TGA) of samples at the ages of 3 and 56 d (the derivative TG (DTG) and weight reduction curves of the steam curing and room temperature curing specimens are classified according to age, and the combustion materials are selected according to the temperature range). The R10 sample exhibited a weight loss similar to that of R20 at an early age, but it had the highest weight loss of all samples at the age of 56 d. This indicates that most hydrates were formed in the R10 sample, which is obvious in its XRD peak intensity. Moreover, the hydration degree of the specimen with a WGB content of 10% was higher in the case of room temperature curing. In addition, in S-group specimens, those specimens with the highest weight losses at the ages of 3 and 56 d were SP and S20, respectively. This indicates that internal curing is more effective as age increases and is considered to influence the improvement of the internal curing of WGB after steam curing. R-group specimens showed proportional results with increasing weight loss and increasing WGB mixing rate as age increased. Thus, internal curing by WGBs was performed in R20, in contrast to RP, which was sealed inside as age increased. Considering a major weight loss, the AFm phase-related dehydration of C-S-H and ettringite occurs at 100 \({}^{\circ}\)C or less; moreover, the evaporation of bound water in the physically bound matrix occurs at 130 \({}^{\circ}\)C. Dehydroxylation of portlandite then occurs until 400-450 \({}^{\circ}\)C, followed by the decarbonation of calcium carbonate and unreacted clinker between 500 and 700 \({}^{\circ}\)C [45; 46; 47; 48]. At an early age, portlandite was apparently consumed for some level of hydration as age increased, confirming the occurrence of pozzolanic reaction. This led to a larger change in R-group specimens, and the consumption of portlandite increased as WGB content increased. All samples showed similar tendencies, indicating that significant initial hydration occurred because of the curing environment, such as steam curing. Table 5 summarizes the relative weight loss due to the dehydration of C-S-H and ettringite, dehydroxylation of portlandite, and decarbonation of unreacted clinker. The weight loss trend below 200 \({}^{\circ}\)C clearly decreased with long-term age, and the decrease rate was larger in the case of steam curing specimens. The ratio of Ca(OH)\({}_{2}\) produced was similar for both steam curing and room temperature curing on the 56 th day.