For the concrete protcol, we refer the reader to ASTM C856-95, Standard Practice for Petrographic Examination of Hardened Concrete [108].

          The microscopic observations are summarized in Table 11 below.

          The following figures show petrographic images of concrete.

Figure 146 Calcium Hydroxide rich paste in 1CON5_3P, 40x, cross polarized light

Figure 147 Same as Figure 146, plane polarized light

Figure 148 Decomposed Calcium Hydroxide (carbonated) in 1CON5_3P, 40x cross polarized light

Figure 149 Same as Figure 148, plane polarized light

Figure 150 Transition between normal and decomposed Calcium Hydroxide in 1CON5_3P

Figure 151 Same as Figure 150, plane polarized light

Figure 152 Carbonation of paste in 1CON5_3P, 40x, cross polarized light

Figure 153 Same as Figure 152, plane polarized light

Figure 154 Carbonation around aggregate in 1CON5_3P, 40x, cross polarized light

Figure 155 Same as Figure 154, plane polarized light

Figure 156 Transition between normal and decomposed Calcium Hydroxide in 1CON5_3P

Figure 157 Same as Figure 156, plane polarized light

Figure 158 Transition between normal and decomposed Calcium Hydroxide in 2CON2-6K

Figure 159 Same as Figure 158, plane polarized light

Figure 160 Transition between normal and decomposed Calcium Hydroxide in 2CON2-6K

Figure 161 Same as Figure 160, plane polarized light

          The following figures show the SEM examination of 1CON5_3P at the surface and at 4 mm and 12 mm depths from the exposed surface.

Figure 162 SEM images of 1CON5_3P at surface

Figure 163 SEM images of 1CON5_3P at 4 mm depth

Figure 164 SEM images of 1CON5_3P at 12 mm depth

          The following figures, Figure 165 through Figure 168, will show the SEM images of hcp subjected to known temperatures from Malhotra [126, Figures 1-10]. They provide a basis for comparison with the images gathered during this experimental research.

Figure 165 SEM micrographs of the CH, Ettringite, and C-S-H crystals: unheated, heated to 250°C and 400°C

Figure 166 SEM micrographs of the CH, Ettringite, and C-S-H crystals: heated to 500° C, 750° C, and 900° C

Figure 167 SEM micrographs of the CH, Ettringite, and C-S-H crystals: 900° exposure and a broken outer surface

Figure 168 SEM micrographs of the CH, Ettringite, and C-S-H crystals: fibrous type I C-S-H and the microstructure of normal concrete