Abstract: C3 S synthesized with analytically pure compounds and nano-SiO2 were used to prepare pastes . The electrical properties , phase composition and specific surface area of the pastes were characterized by means of ζpotential measurement , X-ray diffraction and adsorption-desorption of N 2 , respectively .The adsorption and desorption properties of K +and Na +by the pastes mixed with de-ionized water or alkali solutions were investigated .The results show that the higher the replacement level of nano-SiO2 , the larger the ability of C 3 S-nano-SiO2 pastes to bind alkali .There is no obvious difference between amount of K+and Na +adsorbed by the pastes .Adsorption of K +and Na +by the pastes mixed with de-ionized water is mainly with physical adsorption .There are few residual alkali ions in the pastes mixed with alkali solutions after washed with enough de-ionized water .

Key words: C3 S-nano-SiO2 paste;adsorption;desorption;K+;Na+