Hydration characteristics and environmental friendly performance of a cementitious material composed of calcium silicate slag

Na Zhang; Hongxu Li; Yazhao Zhao; Xiaoming Liu

doi:10.1016/j.jhazmat.2015.11.055

Hydration characteristics and environmental friendly performance of a cementitious material composed of calcium silicate slag

J Hazard Mater. 2016 Apr 5:306:67-76. doi: 10.1016/j.jhazmat.2015.11.055. Epub 2015 Dec 2.

Authors

Na Zhang¹, Hongxu Li¹, Yazhao Zhao², Xiaoming Liu³

Affiliations

¹ School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China; Beijing Key Laboratory of Rare and Precious Metals Green Recycling and Extraction, University of Science and Technology Beijing, Beijing 100083, China.
² School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China.
³ School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China; Beijing Key Laboratory of Rare and Precious Metals Green Recycling and Extraction, University of Science and Technology Beijing, Beijing 100083, China. Electronic address: liuxm@ustb.edu.cn.

PMID: 26691955
DOI: 10.1016/j.jhazmat.2015.11.055

Abstract

Calcium silicate slag is an alkali leaching waste generated during the process of extracting Al2O3 from high-alumina fly ash. In this research, a cementitious material composed of calcium silicate slag was developed, and its mechanical and physical properties, hydration characteristics and environmental friendly performance were investigated. The results show that an optimal design for the cementitious material composed of calcium silicate slag was determined by the specimen CFSC7 containing 30% calcium silicate slag, 5% high-alumina fly ash, 24% blast furnace slag, 35% clinker and 6% FGD gypsum. This blended system yields excellent physical and mechanical properties, confirming the usefulness of CFSC7. The hydration products of CFSC7 are mostly amorphous C-A-S-H gel, rod-like ettringite and hexagonal-sheet Ca(OH)2 with small amount of zeolite-like minerals such as CaAl2Si2O8·4H2O and Na2Al2Si2O8·H2O. As the predominant hydration products, rod-like ettringite and amorphous C-A-S-H gel play a positive role in promoting densification of the paste structure, resulting in strength development of CFSC7 in the early hydration process. The leaching toxicity and radioactivity tests results indicate that the developed cementitious material composed of calcium silicate slag is environmentally acceptable. This study points out a promising direction for the proper utilization of calcium silicate slag in large quantities.

Keywords: Calcium silicate slag; Cementitious material; Environmental friendly performance; High-alumina fly ash; Hydration products.

Publication types

Research Support, Non-U.S. Gov't