Abstract
An experimental study was conducted to investigate the ability of municipal solid waste bottom ash as a resource of cement. Bottom ash contains a large amount of chlorine, and insoluble chlorine such as Friedel’s salt in bottom ash has remained as a problem.
Friedel’s salt forms by a chemical reaction between C3A(3CaO&middit;Al2O3) and CaCl2, and it has been reported as a “poorly understood phase in the CaO-Al2O3-CaCl2-H2O system”. The solubility of Friedel’s salt increases with increasing degree of carbonation and decreasing pH. In this study, the possibility of Friedel’s salt formation from compounds other than for C3A, and Friedel’s salt decomposition by sulfuric acid ion are examined.
The conclusions of this study are as follows: 1) Bottom ash contain not less than two insoluble chlorines of Friedel’s salt (formed from C3A) and hydrocalumite (formed from compounds except for C3A). 2) Friedel’s salt in bottom ash converted to ettringite under a circumstance with a high sulfuric acid ion concentration.
