Efflorescence inhibition and microstructure evolution of Portland cement-based artificial stone induced by mineral additives

Portland cement-based artificial stone is one of the most important construction materials, but the high risk of efflorescence limits its application. Metakaolin, nano-SiO2 and basalt powder were used as mineral additives in Portland cement stone to inhibit efflorescence in this work. The efflorescence of cement stone was investigated from perspectives of hydration products and pore structure. Both morphology and phase assemblage of efflorescence substance was studied through optical microscope, laser confocal Raman spectroscopy and SEM at various scales. Results show that the addition of nano-SiO2 and metakaolin can effectively inhibit the efflorescence of cement stone, due to the consumption of Ca(OH)2 during cement hydration and the decline in total porosity. By contrast, nano-SiO2 with higher reactivity and specific surface area exhibits the best efflorescence resistance, accompanied with the least amount of macro-pores and total porosity, the lowest capillary absorption coefficient and portlandite content.