Title: Interfacial Transition Zone of Alkali-Activated Slag Concrete

Author(s): Tao Ji, Qiaoling Gao, Wenyuan Zheng, Xujian Lin, and Hwai-Chung Wu

Publication: Materials Journal

Volume: 114

Issue: 3

Appears on pages(s): 347-354

Keywords: activator types; Ca/Si ratio; microhardness; presoaked ceramsite; sodium sulfate

DOI: 10.14359/51689473

Date: 5/1/2017

Abstract:
In this study, both micro and macro tests were performed to investigate the effect of activator types on the characteristics of the interfacial transition zone (ITZ) in alkali-activated slag concrete (AASC) with presoaked ceramsite. Two types of chemical activators (Na2SO4 and Na2SO4 plus water glass) were used, each leading to unique cement products. Microhardness was measured within ITZ and analyzed together with microstructure observations by scanning electron microscopy (SEM). Macroscopic properties, including compressive strength and splitting tensile strength, were also measured. For the AASCs with natural coarse aggregate and ceramsite activated by Na2SO4, the microhardness and the Ca/Si ratio of the ITZ are lower than that of portland-cement concrete (PC). For the natural coarse aggregate-AASC activated by Na2SO4 plus water glass, the microhardness of the ITZ is higher than that of PC, and the Ca/Si ratio of the ITZ is lower than that of PC; replacing natural coarse aggregate with ceramsite, the microhardness of the ITZ improves further.