Abstract
Calcium silicate briquettes were hydrothermally made from the raw materials of waste coal ash which were activated by pretreating with 0.05mol/l-HCl solution or 0.1mol/l-NaOH solution at 80°C for 4 hours. After curing for 72 hours, the briquette consisted of hydrogarnet, C-S-H, and tobermorite. The briquette made from the pretreated coal ash had lower bending strength and lower bulk density than those made from untreated coal ash. To improve the strength, waste silica containing 85wt% α-quartz was added with the pretreated coal ash. The pretreatment of coal ash indirectly improved the reactivity of waste silica, since hydrothermal solution easily invaded into the briquette through pore developed by the reaction of coal ash. The briquettes having bending strength of 18.7MPa and bulk density of 1.42Mg/m3 were obtained.
