Influences of Fly Ash on the Compressive Strength and Hydration Products of Magnesium Oxysulfate Cement

Magnesium oxysulfate cement (MOS) pastes mixed with different amounts of fly ash were tested on the compressive strength. The examinations of strength development, phase compositions and microstructure of MOS cement are discussed in detail. Results showed that the compressive strength of MOS cement specimens decreased with increasing fly ash content from 0% to 50% at the curing age 1 day. Moreover, the effects of fly ash on the compressive strength of MOS cement have relation to the molar ratio of H₂O/MgSO₄. Very fine particles of fly ash trap more capillary water and yields micro porosities and filling voids in MOS cement which would result increased compressive strength at the higher content.