Experimental study of magnesium ammonium phosphate cements modified by fly ash and metakaolin

Abstract

In order to make anti-corrosion coating for steel structure, the prepared MAPC paste should meet the requirements of spraying process and require high fluidity. The purpose of this paper is to prepare MAPC paste with high fluidity. but too high water-cement ratio will lead to the decrease of strength. In order to solve this problem, mineral admixtures are added to improve the performance of MAPC. The strength, fluidity, volume deformation, hydration temperature, early water stability, microstructure and phase composition of fly ash or metakaolin modified high fluidity MAPC paste were tested and analyzed. The results show that the addition of mineral admixture can effectively improve the performance of high fluidity MAPC paste without decreasing the fluidity of the paste, in which metakaolin can improve the strength of MAPC paste better than fly ash; this is due to the formation of more highly reinforced microstructures and denser interfaces between the metakaolin particles and hydration products in the MAPC paste containing metakaolin. Based on the micro-analysis of XRD, SEM and energy dispersive spectrometer (EDS), the improvement mechanism was discussed.