Early mechanical properties and microstructural evolution of slag/metakaolin-based geopolymers exposed to karst water. (May 2019)

• Record Type: Journal Article
• Authors: Xiang, Jichun; Liu, Leping; He, Yan; Zhang, Ning; Cui, Xuemin
• Is Part Of: Cement & concrete composites. Volume 99(2019)
• Page Start: 140
• Page End: 150
• Publication Date: 2019-05
• Subjects: Karst water corrosion -- Geopolymer -- Pore structure -- Slag -- Microstructure; Composite-reinforced concrete -- Periodicals; Concrete -- Periodicals; Composite materials -- Periodicals; Composites de ciment -- Périodiques; Béton -- Périodiques; Composites -- Périodiques; Béton léger -- Périodiques; Cement composites; Composite materials; Composite-reinforced concrete; Concrete; Lightweight concrete; Periodicals; Electronic journals; 620.135
• DOI: 10.1016/j.cemconcomp.2019.03.009
• Languages: English
• ISSNs: 0958-9465

Abstract

Abstract: As a type of corrosive mixed solution, karst water contains not only chloride and sulfate ions, but also a significant amount of bicarbonate ions. The early mechanical properties and microstructure of a metakaolin-based geopolymer and metakaolin/slag geopolymers (with 20 and 40 wt% slag replacing the metakaolin) immersed in karst water were investigated using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Barrett-Joyner-Halenda (BJH) analysis, and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS). The results showed that a reduction in mechanical strengths associated with variations in the pore size, excess of alkalis (Na2 O), decalcification of C-S-H, and calcium carbonate precipitation occurred after immersion in karst water. Furthermore, the geopolymers with the addition of less slag had a greater ability to resist corrosion by karst water. This is related to the formation of calcium carbonate in the calcium-rich geopolymer, along with the excess of alkali (Na + ) for activated slag led to dissolve to the karst water.