THE EFFECT OF SILICA FUME ON THE DURABILITY OF MAGNESIUM OXYCHLORIDE CEMENT

This paper investigated the water resistance of magnesium oxychloride cement (MOC) incorporating silica fume + phosphoric acid + nano-silica (SPN). Strength retention was tested to evaluate the water resistance of MOC. The characterisation of the hydration products and the microstructure of the typical samples before and after water immersion were carried out by using X-ray diffraction (XRD) and scanning electron microscope (SEM) facilities. The results show that incorporation of SPN significantly enhances the water resistance of MOC. The generation of an insoluble magnesium-chloride-silicate-hydrate gel and a magnesium-chloride-hydrate gel and the densification of the microstructure contribute to the remarkable improvement in the water resistance of MOC. Meanwhile, the pore structure results show that the total porosity and permeability of MOC has no direct relevant relationship on the improvement of the water resistance at the time of 28-day air curing.