Abstract
The discharge amount of coal ash was around 10 million tons every year from all coal-fired power plants, so there is a need to obtain new efficient usage of fly ash. Recently, aluminosilicate material processed by alkali activation attracts attention as structural material. In this study, authors reported that the paste mixing fly ash with alkali hydroxide solution and curing under hydrothermal condition has high strength and high content of zeolites. Zeolites usually have cation exchange ability, so this hardened material was expected to have an ability to remove hazardous trace elements. This study discusses the mechanical property, microstructure and cation exchange ability of this proposal material that cured under hydrothermal condition at 140℃ and 180℃. The crystalline and glassy products in the hardened material were identified by XRD, the pore size distribution was measured by mercury intrusion porosimetry. The fracture surface and polished surface were observed by SEM and EPMA respectively. The adsorption properties for cesium cadmium, and lead were measured, and the CEC was measured by Wada and Harada’s method. The compressive strength and bending strength of hardened body cured at 180℃ were 48.6 N/mm2 and 8.42 N/mm2 respectively. Main product was Gmelinite, and its plate shaped crystalline were precipitated among fly ash particles. The CEC of proposed material was 128cmol/kg, and it has good adsorption property against cesium, cadmium and lead ions. In addition, this material has much better moldability than conventional zeolite used materials.
