Sodium Dihydrogen Phosphate and Sodium Stearate Compound Modified Foamed Magnesium Oxysulfate Cement

The foamed magnesium oxysulfate cement (FMOSC) samples prepared by the composite modification and single-admixture modification of sodium dihydrogen phosphate (SDP) and sodium stearate (SS) were compared. The effect of compound modifier on dry density, porosity, pore structure, pore size distribution, compressive strength and softening coefficient of FMOSC were studied. The phase composition and microscopic morphology of hydration product were studied by X-ray diffraction, infrared spectra and scanning electron microscopy. The results show that SDP and SS have a slight influence on the dry density and porosity of the sample, the pore structure and pore size distribution are optimized, and the compressive strength and softening coefficient are more than two times higher than before modification by composite modification. In the meantime, the effect of the composite modification is better than that of single modification. The main hydrate product of FMOSC is Mg(OH)2 after the addition of SS and 517 phase when the SDP have been introduced. It is indicated that the H2PO4- can adsorb on the surface of hydrated magnesium oxide, inhibiting the formation of Mg(OH)2 and promoting the formation of 517 crystal nucleus. During the self-assembly process of crystal nucleus to form 517 crystal phase, the C17H35COO- adsorbed on the surface of crystal nucleus and affected the morphology of 517 crystal. Under the double action of SDP and SS, the FMOSC with advantages of lightweight, high strength and excellent water resistance have been prepared. © 2021, Materials Review Magazine. All right reserved.