# Impact of Temperature on the Moisture Buffering Performance of Palm and Sunflower Concretes
## 4 Numerical Study and Discussions  
Influence of Temperature on the Moisture Buffering Capacity and Classification of Bio-Based Materials  
The experimental studies carried out on palm concrete (PC) showed that the temperature has a significant impact on the MBV. Therefore, a study focusing on the influence of the temperature on the moisture buffering capacity is necessary in order to evaluate, analyze and optimize the hygric performance of bio-based materials. In this section, the physical model and the boundary conditions are the same as the ones used in the section dedicated to the model validation. A wall thickness of 10.0 cm is considered for both bio-based concretes (PC and SC). The simulations are performed on a range of temperatures which vary from 10 to 35 \({}^{\circ}\)C, with a step of 5 \({}^{\circ}\)C. The hygothermal properties used are the ones obtained experimentally and presented in Figure 1 and Table 2. The outputs of the simulation are the mass variation of the samples according to the variation in the indoor relative humidity and MBV at different temperatures. The numerical values of the MBV of two materials are calculated, compared and presented in Figure 5. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**T (\({}^{\circ}\)C)**} & \multirow{2}{*}{**P\({}_{n,sat}\) (Pa)**} & \multirow{2}{*}{\(\rho_{v,e}\) (g/m\({}^{3}\))**} & \multirow{2}{*}{**P\({}_{v}\) (Pa)**} & \multirow{2}{*}{\(\rho_{v,e}\) (g/m\({}^{3}\))**} & \multirow{2}{*}{**P\({}_{v}\) (Pa)**} \\  & & & **at 33\%** & & **at 75\%** & **at 75\%** \\ \hline
10 & 1241.2 & 3.13 & 409.6 & 7.1 & 930.9 \\ \hline
15 & 1724.2 & 4.3 & 569 & 9.7 & 1293.1 \\ \hline
20 & 2364.9 & 5.8 & 780.4 & 13.1 & 1773.7 \\ \hline
23 & 2842.1 & 6.9 & 937.9 & 15.6 & 2131.6 \\ \hline
25 & 3205.2 & 7.7 & 1057.7 & 17.5 & 2403.9 \\ \hline
30 & 4295 & 10.1 & 1417.7 & 23 & 3221.3 \\ \hline
35 & 5693.8 & 13.2 & 1879 & 30 & 4270.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Influence of temperature on vapor pressure and water vapor concentration. Figure 4: Sample mass variation at 23 \({}^{\circ}\)C for PC case: model validation. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Materials**} & \multirow{2}{*}{\
\begin{tabular}{c} **Experimental MBV** \\ **(g/(m\({}^{2}\)\(\diamond\)RH))** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Numerical MBV** \\ **(g/(m\({}^{2}\)\(\diamond\)RH))** \\ \end{tabular} } \\  & & 2.03 at 10 \({}^{\circ}\)C & 2.01 at 10 \({}^{\circ}\)C \\  & and 2.96 at 23 \({}^{\circ}\)C & and 2.99 at 23 \({}^{\circ}\)C \\ \hline SC & 2.26 at 23 \({}^{\circ}\)C & 2.29 at 23 \({}^{\circ}\)C \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Experimental and numerical MBVs of PC and SC concretes. In Figure 5, it can be observed that increasing the temperature will increase the moisture buffer value. As explained above, this is due to the fact that increasing the interior temperature will influence the vapor pressure gradient of the surrounding environment. Table 4 and Figure 6 show the dependence of the saturation pressure of water vapor on the studied range of temperatures, going from 10 to 35 \({}^{\circ}\)C, and the vapor pressure/water vapor concentration as a function of the temperature and relative humidity. At a temperature of 10 \({}^{\circ}\)C, when the surrounding relative humidity varies from 33% to 75%, the water vapor pressure P\({}_{v}\) varies from 409.6 to 930.9 Pa (\(\Delta\)P\({}_{v}\) = 521.3 Pa) compared to the variation from 1879 to 4270.4 Pa (\(\Delta\)P\({}_{v}\) = 2391.4 Pa) at a temperature of 35 \({}^{\circ}\)C. This significant difference in the water vapor pressure gradient results in a significant influence on the MBV obtained and classification, as shown in Figure 5.  
Most bio-based concretes are excellent regulators of indoor relative humidity. This is due to the microstructure of vegetal particles (see Figures 7 and 8) that are incorporated in bio-based concretes.