FTIR investigations
FTIR investigations on the bottom ash and foamed bricks are shown
in Fig. 5. Infrared spectroscopy reveals a significant broad band around3400 cm−1 and 1630 cm−1 corresponding to OH stretching and bending
respectively for the pure bottomash [22,23]. These bands are almost
absent in the foams, indicating the full dehydration of the sample. The
SiOT (T: Si or Al) asymmetric stretching vibration for the bottom
ash is detected at 1092 cm−1 while this vibration for the foams is
present at 1004 cm−1. This shifting of wave number indicates that the
SiOT (T: Si or Al) molecular structure is more long ranged compared
to the bottom ash hence bigger molecules were formed during microwave
curing; hence a higher degree of crosslinking [24]. However the
relative degree of polymerization of foams, based on their SiOT
(T: Si or Al) peak height and peak area, decreases as the bottom ash
content increased. The first reason is that as the bottom ash content
increases, the amount of silica from sodium silicate to create the silica–
alumina network decreases and secondly, while decreasing the