Characterisation of magnesium potassium phosphate cements blended with fly ash and ground granulated blast furnace slag. (August 2015)

• Record Type: Journal Article
• Authors: Gardner, Laura J.; Bernal, Susan A.; Walling, Samuel A.; Corkhill, Claire L.; Provis, John L.; Hyatt, Neil C.
• Is Part Of: Cement and concrete research. Volume 74(2015)
• Page Start: 78
• Page End: 87
• Publication Date: 2015-08
• Subjects: Microstructure (B) -- SEM (B) -- Fly ash (D) -- Granulated blast furnace slag (D) -- Chemically Bonded Ceramics (D); Cement -- Periodicals; Cement -- Research -- Periodicals; Concrete -- Periodicals; Concrete -- Research -- Periodicals; Ciment -- Périodiques; Béton -- Périodiques; Cement; Concrete; Periodicals; 620.135
• DOI: 10.1016/j.cemconres.2015.01.015
• Languages: English
• ISSNs: 0008-8846

Abstract

Abstract: Magnesium potassium phosphate cements (MKPCs), blended with 50 wt.% fly ash (FA) or ground granulated blast furnace slag (GBFS) to reduce heat evolution, water demand and cost, were assessed using compressive strength, X-ray diffraction (XRD), scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) spectroscopy on 25 Mg, 27 Al, 29 Si, 31 P and 39 K nuclei. We present the first definitive evidence that dissolution of the glassy aluminosilicate phases of both FA and GBFS occurred under the pH conditions of MKPC. In addition to the main binder phase, struvite-K, an amorphous orthophosphate phase was detected in FA/MKPC and GBFS/MKPC systems. It was postulated that an aluminium phosphate phase was formed, however, no significant Al–O–P interactions were identified. High-field NMR analysis of the GBFS/MKPC system indicated the potential formation of a potassium-aluminosilicate phase. This study demonstrates the need for further research on these binders, as both FA and GBFS are generally regarded as inert fillers within MKPC.