## 3 Results and Discussion  
### Physical-Mechanical Characterization  
The AAMs' residual properties were characterized as a function of temperature (up to 1100 \({}^{\circ}\)C) and heating rate (1 and 10 \({}^{\circ}\)C/min). Figure 2 illustrates the color change, cracking, and deformation of the mortars after high-temperature exposure. Below 750 \({}^{\circ}\)C, there were no visible effects on the surface of the specimens independent of the heating rate used. Similar observations have been made by [PERSON] et al. [23] in fly ash/GGBPS mortars. Only a slight lightening of the color could be observed from 20 \({}^{\circ}\)C (Figure 2a) to 600 \({}^{\circ}\)C (Figure 2b), which can be attributed to gradual dehydration and some Fe oxidation as shown by [PERSON] et al. [24]. In fact, Figure 3 shows that mass loss mainly occurred in this temperature range. The mass loss at 105 \({}^{\circ}\)C can be attributed to the evaporation of free water located in existing pores. Previous works [7] have reported a higher mass loss in this temperature range, which can be explained--along with the differences in binder chemistry--by the curing conditions (50 \({}^{\circ}\)C for 3 d) and curing duration (28 d) prior to thermal testing employed in this work. Thus, part of the water has already evaporated before the experiment when following this procedure. The further mass loss observed at temperatures up to 600 \({}^{\circ}\)C can be attributed to the egress of water present in smaller sized pores, interstitial water, and chemically bonded water in hydroxyl groups [11,14]. No anisotropic features were detected, and a uniform volumetric contraction that did not exceed 20 vol% was observed. [PERSON] et al. [24] reported significant lower shrinkage values in Fe-rich AAMS (3% at 900 \({}^{\circ}\)C) while [PERSON] et al. [25] refer to shrinkage values of 5% in FA geopolymers fired at temperature of 800 \({}^{\circ}\)C. The influence of the heating rate started to become evident from 750 \({}^{\circ}\)C, as shown in Figure 2c-h. The specimens heated at lower rates (1 \({}^{\circ}\)C/min) changed color from a light grey to a gradually more brownish and yellow color (see Figure 2c,e,g). No cracks were visible on the surfaces of these samples, and the absence of color gradients indicates uniform mineralogical transformations [24]. The mineralogical transformations that occurred at these temperatures explain the changes in color and are discussed later in this work. Figure 2: Alkali activated mortar specimens after 28 d of curing and thermal exposure to: (**a**) 20 \({}^{\circ}\)C; (**b**) 600 \({}^{\circ}\)C; (**c,d**) 750 \({}^{\circ}\)C with heating rates of 1 and 10 \({}^{\circ}\)C/min, respectively; (**e,f**) 900 \({}^{\circ}\)C with heating rates of 1 and 10 \({}^{\circ}\)C/min, respectively; (**g,h**) 1100 \({}^{\circ}\)C with heating rates of 1 and 10 \({}^{\circ}\)C/min, respectively. Mortars exposed to 105 \({}^{\circ}\)C are not shown here, but no significant modifications of specimens’ appearance could be seen relative to the ones kept at 20 and 600 \({}^{\circ}\)C (**a**). At 600 \({}^{\circ}\)C there were no visible differences between specimens heated with distinct heating rates, with (**b**) being a representative example of both. Molten material at the surface of mortars heated up to 1100 \({}^{\circ}\)C at 10 \({}^{\circ}\)C/min is illustrated in (**h**). When a higher heating rate was employed (10 \({}^{\circ}\)C/min), less distinguishable color changes were observed. The specimens heated up to 750 and 900 \({}^{\circ}\)C presented a less vivid brownish color relative to the ones heated at lower heating rates. Some color gradients were observed across the specimens' surfaces, especially when heated to 900 \({}^{\circ}\)C. The differences in color indicate that temperature gradients may have led to uneven transformations as suggested elsewhere [24]. In addition, some cracks and superficial degradation were visible on the surface of samples.