## 3 Results and Discussion
### Young's Modulus, Dynamic Shear Modulus, Poisson Ratio and Compressive Strength
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Properties**} & \multirow{2}{*}{**Temperature [\({}^{\circ}\)C]**} & \multicolumn{5}{c}{**Mortar**} \\ \cline{3-6}  & & **A** & **B** & **C** & **D** & **E** \\ \hline \multirow{4}{*}{Dynamic shear modulus[MPa]} & 20 & 1349 (71) & 98 (14) & 66 (4) & 2826 (139) & 3230 (97) \\ \cline{2-6}  & 100 & 955 (82) & 124 (45) & 122 (2) & 3369 (1091) & 3000 (317) \\ \cline{2-6}  & 150 & 888 (68) & 128 (46) & 64 (2) & 2606 (411) & 2223 (179) \\ \cline{2-6}  & 200 & 1177 (35) & 140 (10) & 99 (4) & 5213 (180) & 2178 (57) \\ \cline{2-6}  & 250 & 1379 (137) & 99 (29) & 86 (1) & 4455 (110) & 1387 (324) \\ \hline \multirow{4}{*}{Poisson ratio[–]} & 20 & 0.17 (0.05) & 0.23 (0.16) & 0.30 (0.00) & 0.30 (0.00) & 0.13 (0.11) \\ \cline{2-6}  & 100 & 0.18 (0.08) & 0.29 (0.02) & 0.08 (0.01) & 0.24 (0.09) & 0.18 (0.06) \\ \cline{1-1} \cline{2-6}  & 150 & 0.15 (0.06) & 0.20 (0.12) & 0.30 (0.00) & 0.30 (0.00) & 0.11 (0.03) \\ \cline{1-1} \cline{2-6}  & 200 & 0.12 (0.02) & 0.17 (0.07) & 0.30 (0.00) & 0.12 (0.04) & 0.12 (0.05) \\ \cline{1-1} \cline{2-6}  & 250 & 0.14 (0.04) & 0.31 (0.10) & 0.16 (0.12) & 0.11 (0.04) & 0.05 (0.02) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Summary of dynamic shear modulus and Poisson ratio: average and standard deviation (in parentheses). Figure 6: Compressive strength (%) vs. exposure temperature. Between 150 \({}^{\circ}\)C and 200 \({}^{\circ}\)C there was an increase in compressive strength in mortars A\({}^{\text{EC}}\) and D\({}^{\text{ref}}\) and stabilization in mortars B\({}^{\text{GEC}}\) and E\({}^{\text{AD}}\). This behavior is due to the competing effects of acceleration of hydration of the non-hydrated cement and degradation due to microcracking [49]. This hydration results from the passage of water vapor released by the pores originating steam condition under the effect of the so-called internal autoclaving that occurs from 160 \({}^{\circ}\)C to 220 \({}^{\circ}\)C in cement-based materials [58; 59]. After 200 \({}^{\circ}\)C, decomposition of C-S-H gel and the sulfoaluminate phase cause cracks with significant effect on the compressive strength [60]. Despite the considerable relative variation, the smaller variation of the compressive strength (in absolute value) of expanded clay mortar compared to sand mortars may be justified by a greater compatibility of the coefficient of thermal expansion (CET) of cement paste with that of expanded clay when compared to sand [50]. The different magnitudes of the compressive strength changes point out the importance of considering the CET of the aggregates in mortars exposed to elevated temperatures. Thus, when analyzing the variation in compressive strength with increasing temperature, the largest variations (1.06 MPa in mortar D\({}^{\text{ref}}\) and 2.44 MPa in mortar E\({}^{\text{AD}}\)) occurred in mortars with sand (with CET between 10 and 13 \(\times\) 10-6 \({}^{\circ}\)C\({}^{-1}\)[61]), followed (0.9 MPa) by the AEC mortar with expanded clay (with CET between 6 and 10 \(\times\) 10-6 \({}^{\circ}\)C\({}^{-1}\)[61]). The mortar with the lowest variation in compressive strength (0.24 MPa) was the C\({}^{\text{AERO}}\) mortar with silica aerogel, which has the lowest CET (between 2 and 4 \(\times\) 10-6 \({}^{\circ}\)C\({}^{-1}\)[62]) among all aggregates under study. Although granulated expanded cork has a high CET (between 25 and 50 \(\times\) 10-6 \({}^{\circ}\)C\({}^{-1}\)[63]), it also has a high compressibility [64], which may explain the small variation in compressive strength (0.27 MPa) of mortar B\({}^{\text{GEC}}\). Thus, the major effects (reduction and increase in density and mechanical resistance) caused by increasing temperature are essentially due to the temperature influence on the cement paste. This study shows that the magnitude of those effects depends significantly on the types of aggregates, namely their thermal expansion coefficient and compressibility.