## 3 Results and Discussion  
### TGA Observations  
Figure 8 shows the evaporation curves of the PCM and GPCM, respectively. The examination of the PCM's and GPCM's respective TGA curves shows that the two curves behaved very differently. The slope (dw/dt) of each curve indicates the material's weight loss rate. For the PCM curve, the evaporation took place immediately, and almost 3% of the mass was lost at a temperature of 50 \({}^{\circ}\)C. As the temperature increased, the weight loss increased. It is clearly shown that the rate of weight loss was almost constant after 50 wt% losses till it completely evaporated at about 150 \({}^{\circ}\)C. For the GPCM paste, three phases were observed in the evaporation curve. In the first stage, there was a steady stage, at which there was no weight loss as the temperature increased to 125 \({}^{\circ}\)C (in other words, the slope of dw/dt = 0). In the second phase, the weight loss started at 125 \({}^{\circ}\)C and reached 50 wt% losses at 250 dw/dt. However, the final phase was similar to the first phase, where almost no weight loss was observed till the end of the test.  
It is worth mentioning that when GP was added to PCM (GPCM) in a ratio of 50:50, the maximum weight loss of the PCM occurred at about 250 \({}^{\circ}\)C. However, when the ratio of the GP:PCM was 0:100 (PCM only), the maximum weight loss of the PCM took place at 150 \({}^{\circ}\)C. The delay in the maximum evaporation temperature was attributed to the ability of the GP material (powder form) to absorb PCM (liquid form). The explanation of this mechanism is that the pores in the GP were able to form in a semi-shell-like shape, delaying the evaporation process of the PCM. The fact that glass has a relatively low thermal conductivity has most likely also contributed to delaying the evaporation of the PCM retained in PG particles.  
In addition, the TGA test was conducted on the control, 5%PCM, and 7%GPCM binders. Table 4 summarizes the initial, medium, and maximum evaporation temperatures of these binders.  
TGA results showed that the evaporation temperature of the PCMs alone was relatively low. This low gradation temperature created a challenge in maintaining the mass of PCMs in the asphalt mixture to achieve its anticipated benefits. For this reason, use of PCMs in hot mix asphalt cannot be evaluated. Moreover, to mitigate the risk of PCM evaporation during the production process, it is recommended to use PCMs with warm or half-warm mix asphalt (WMA and HWMA), as the production temperature of these mixes is typically lower than 150 \({}^{\circ}\)C. The PCMs can also help reduce the viscosity of the binder during the mixing and compaction, which can facilitate the conduction of these operations at lower temperatures.  
TGA analysis indicated that the PCMs had a thermal decomposing temperature significantly lower than the mixing temperature of the PG70-28 binder. It is reported that SBS-modified binders have higher mixing and compaction temperatures than straight-run binders, as the SBS increases the viscosity and reduces the pumpability of the binder [23]. As a result, using this type of PCM is not compatible with polymer-modified binder as it is expected that severe evaporation can happen to the PCM during the production of the asphalt mix.