# Assessment of Lightweight Concrete Thermal Properties at Elevated Temperatures
## 3 Results and Discussion
### MTPS Results
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Type of Concrete** & **Sample** & **Moisture Content (\%)** &
\begin{tabular}{c} _k (T = 20 \({}^{\circ}\)C)_ \\ **W/mK** \\ \end{tabular} \\ \hline LWC-1 & A & \(3.1\pm 0.1\) & 1.228 \\ LWC-1 & B & \(5.8\pm 0.1\) & 1.596 \\ LWC-1 & C & \(6.2\pm 0.1\) & 1.619 \\ LWC-1 & D & \(6.4\pm 0.1\) & 1.699 \\ \hline LWC-2 & A & \(5.8\pm 0.25\) & 1.499 \\ LWC-2 & B & \(7.4\pm 0.12\) & 1.736 \\ LWC-2 & C & \(7.5\pm 0.1\) & 1.737 \\ LWC-2 & D & \(5.6\pm 0.1\) & 1.470 \\ \hline LWC-3 & A & \(7.3\pm 0.1\) & 1.590 \\ LWC-3 & B & \(6.4\pm 0.1\) & 1.425 \\ LWC-3 & C & \(7.1\pm 0.1\) & 1.562 \\ LWC-3 & D & \(7.6\pm 0.1\) & 1.480 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Moisture content and average thermal conductivity values of LWC samples at ambient temperature. square error. For a moisture content of 7%, the average thermal conductivity values of LWCs vary from 1.917 to 1.505 W/mK, as shown in Table 4. This is significantly lower than the thermal conductivity of normal concrete. The heat transfer and energy consumption are also lower. Figure 6 shows specific heat at elevated temperatures. According to the results, the specific heat behavior of concretes is almost identical for all LWC types. Due to the vaporization of free water in the range of 100 to 140 \({}^{\circ}\)C, specific heat increases. The average test results for thermal conductivity at elevated temperatures are shown in Table 5. For all the LWCs, the thermal conductivity behavior is similar, decreasing linearly with temperatures up to 70 \({}^{\circ}\)C. It then remains almost constant between 70 and 100 \({}^{\circ}\)C, with minor variations attributed to vaporization. Due to the vaporization of free water and the reduction in latent heat, at 100 \({}^{\circ}\)C, there is a slight increase in thermal conductivity, as shown in previous works [4; 12]. The steep slope of thermal conductivity between 100 and 160 \({}^{\circ}\)C can be attributed to moisture loss as a consequence of vaporization of free water with a rise in temperature [12; 41]. All the LWCs show thermal conductivity values at elevated temperatures up to 50% lower tha \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample** & **\(\mathbf{k}\) (LWC-1)** & **\(\mathbf{k}\) (LWC-2)** & **\(\mathbf{k}\) (LWC-3)** \\  & **W/mK** & **W/mK** & **W/mK** \\ \hline A & 2.120 & 1.611 & 1.562 \\ B & 1.888 & 1.695 & 1.477 \\ C & 1.811 & 1.686 & 1.553 \\ D & 1.848 & 1.599 & 1.428 \\ \hline Mean value & 1.917 & 1.648 & 1.505 \\ \(\sigma\) & 0.139 & 0.050 & 0.064 \\ Error (\%) & 7.259 & 3.016 & 4.243 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Fitted values of thermal conductivity for 7% of moisture content. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Type of Concrete** & **Sample** & \(\mathbf{k}\) (70 \({}^{\circ}\)C) & \(\mathbf{k}\) (100 \({}^{\circ}\)C) & \(\mathbf{k}\) (120 \({}^{\circ}\)C) & \(\mathbf{k}\) (160 \({}^{\circ}\)C) \\  & **W/mK** & **W/mK** & **W/mK** & **W/mK** & **W/mK** \\ \hline LWC-1 & A & 1.063 & 1.106 & 0.902 & 0.632 \\ \hline LWC-1 & B & 1.367 & 1.404 & 1.100 & 0.661 \\ LWC-1 & C & 1.492 & 1.531 & 1.127 & 0.670 \\ LWC-1 & D & 1.575 & 1.616 & 1.253 & 0.752 \\ Mean value & 1.478 & 1.517 & 1.160 & 0.679 \\ Standard deviation & 0.225 & 0.223 & 0.145 & 0.051 \\ \hline LWC-2 & A & 1.348 & 1.345 & 1.094 & 0.791 \\ LWC-2 & B & 1.704 & 1.719 & 1.196 & 0.819 \\ LWC-2 & C & 1.630 & 1.663 & 1.209 & 0.828 \\ LWC-2 & D & 1.408 & 1.429 & 1.086 & 0.827 \\ Mean value & 1.522 & 1.539 & 1.146 & 0.816 \\ Standard deviation & 0.171 & 0.181 & 0.065 & 0.017 \\ \hline LWC-3 & A & 1.486 & 1.503 & 1.223 & 0.867 \\ LWC-3 & B & 1.373 & 1.380 & 1.100 & 0.801 \\ LWC-3 & C & 1.437 & 1.537 & 1.182 & 0.853 \\ LWC-3 & D & 1.423 & 1.495 & 1.181 & 0.842 \\ Mean value & 1.430 & 1.479 & 1.171 & 0.841 \\ Standard deviation & 0.046 & 0.068 & 0.052 & 0.028 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Average thermal conductivity values of LWC samples in different high-temperature environments.