*3.5. Infrared Thermography*

In order to evaluate the thermal insulating properties of the cement composites, the infrared thermography (IRT) experiment was carried out on all the samples: CS, E50, E100, CST, E50T, and E100T. Figure 10 illustrates the thermal images of surface temperature distribution of the samples captured by the IRT camera at different heating times. According to the relationship between the color and temperature value, it can be suggested that the heat-transferring rate and thermal conductivity of cement composites were significantly decreased with the inclusion of EGA. The thermal images clearly demonstrate a different temperature distribution in the control sample (CS mix) and the samples containing EGA (E50 and E100 mixes). The results show that the temperature increased rapidly in the CS however, a noticeable slower heat transfer rate observed for samples incorporated with EGA (E50 and E100). The data also revealed a drop in the heat transfer rate as the EGA content increased. For instance, after 15 min the average surface temperature in the CS sample reached 55 ◦C while the average surface temperature in the E50 and E100 samples reached 52.7 and 48.7 ◦C respectively, which shows a temperature difference of 2.3 ◦C and 6.0 ◦C for E50 and E100 respectively. Moreover, the results demonstrated the heat transfer rate of 1.75, 1.60, and 1.35 ◦C/min for CS, E50, and E100 respectively that shows a lower rate for samples

containing EGA (E50 and E100) in comparison to the control sample (CS). This observation was attributed to a high porosity and low thermal conductivity of EGA. Indeed, by incorporation of EGA the air void is replaced with sand, which has a high thermal conductivity. EGA has a thermal conductivity of 0.07 W/mK that is much less than that of sand (Expanded Glass Technologies). Consequently, by replacing the NA with EGA the heat transfer of the cement composite was reduced.

**Figure 10.** Infrared thermography images of different samples.

Table 5 demonstrates the average temperature di fferences for each mix. The thermal charging results for the samples inclusion nTiO2 showed a di fferent trend to the first set of mixes (mixes without nTiO2). It was observed that incorporation nTiO2 increased the heat transfer rate, which is undesired in terms of thermal insulation properties. The thermal images demonstrated that inclusion of nTiO2 into the composite increased the heat transfer rate compared to the samples without nTiO2. For example, after 15 min the average surface temperature in CS, E50, and E100 samples reached to 55 ◦C, 52.7 ◦C, and 48.7 ◦C respectively. While average surface temperature in the CT, E50T, and E100T samples reached to 56.8 ◦C, 55 ◦C, and 49.1 ◦C respectively that shows an increase in the temperature di fference of 1.6 ◦C, 2.3 ◦C, and 1.4 ◦C respectively. Furthermore, the results demonstrated the heat transfer rate of 1.87, 1.76, and 1.38 ◦C/min for CT, E50T, and E100T respectively that indicates higher rate than the samples without nTiO2. It can be concluded that nTiO2 acts as a filler and changes the pore structures of the cement composite and consequently the thermal charging performance of the matrix. Therefore, in terms of thermal properties, NA substitution with EGA improves the thermal insulation properties of cement composites. This positive e ffect is attributed to lower thermally conductive and higher porosity of EGA compared to NA.


**Table 5.** The average temperature di fferences for each mix.
