Effects of different mineral admixtures on the properties of magnesium potassium phosphate cement mortar

Magnesium potassium phosphate cement (MKPC) is one of chemical bonded ceramic material that has more prominent advantages including fast-setting compared to Ordinary Portland Cement. In recent years, although there have been some studies on MKPC and its admixtures, the effects of individual admixture on MKPC have not been well understood. In this paper, the mechanical properties and microstructure of MKPC with mineral admixtures including fly ash (FA), silica fume (SF) and steel slag (SSP) were investigated and compared. Mechanical properties were analyzed by carrying out flexural strength and compressive strength tests. The hydration products and microstructure of MKPC samples with and without mineral admixtures were investigated using X-ray diffraction, energy dispersive X-ray spectrometry, scanning electron microscopy and adsorption isotherm. Based on the test results, it was shown that the optimum addition of FA, SF and SSP additives were found to be 30 %, 20 % and 5 %, respectively. Compared to MKPC without admixture, the flexural strength of MKPC incorporating FA, SF and SSP can be enhanced by 28 %, 40 % and 17.3 %, respectively, while the compressive strength can be improved by 43.4 %, 52.6 % and 6.7 %, respectively. Hence, it can be concluded that the SF has the largest effects on the compressive strength of MKPC, while the effects of SSP is the smallest.