Shrinkage, fire resistance and carbonation characteristics of alkali-activated CFBC ash/slag mortar

Abstract

The number of CFBC (Circulating Fluidized Bed Combustion) type coal-fired power plants are increasing as such plants produce lower NOx, and SOx emissions compared to conventional PC (Pulverized Coal) type coal-fired power plants. CFBC ash contains large amounts of CaO due to the desulfurization process that involves the injection of limestone during combustion. Although the use of coal ash with large amounts of CaO as a construction material results in expansion and decreased durability, CFBC ash was used in this study instead of slag to reduce shrinkage in alkali-activated slag mortar.

Alkali-activated CFBC ash/slag mortar has not been studied from a cement chemistry perspective. This study describes the following: 1) an investigation of the chemical characteristics and CO2 sequestration characteristics of CFBC ash, 2) the identification of the shrinkage mechanism of alkali-activated CFBC ash/slag mortar, and 3) comparison analysis between CFBC ash and conventional alkali-activated slag mortar in terms of characteristics according to exposed to high temperatures as well as carbonation performance characteristics (due to the lack of basic durability research on similar materials. In addition, CO2 emissions were estimated for environmental impact assessment. According to the results, CFBC ash-incorporated cement exhibited less shrinkage and improved durability compared to cement that used conventional alkali-activated slag.