The Study On The Effects Of Surfactant In Alkali-activated Slag Cement System

Alkali-activated slag cement(ASC)is a kind of binding material through alkaline compound activating the slag. Alkali-activated slag concrete has good physical mechanics and durability performance. ASC also is a kind of green building material with some advantages, such as saving energy, reducing waste, and protecting environment. The hydration theory of alkali-activated slag cement and concrete was researched deeply, the problems of control of setting time and the worry of alkaline-aggregate reaction were resolved 1980-1990.The ASC show a larger viscosity and a lower workability under normal water/binder ratio. Therefore, it can not be adapted by modern construction technology and it has been a key technique restricting the development of alkali-activated slag cement and concrete. Adding surfactant is an important technique to solve those problems, but so far the mechanism research of surfactant in alkali-activated slag cement and concrete is rare. The mechanism research on surfactant in alkali-activated slag cement and concrete is an important theoretical basis to determine a suitable plasticizer fitting the special binder material.The effect of variety ,dosage of surfactant and activator on the adsorbed mount of surfactant on the surface of slag was reserched,ζpotential of slag, molecular structure diversification of surfactant, fluidity, strength and setting time of cement paste were analyzed through adsorbed amount test.ζpotential test, fluidity test, setting time test and molecular structure stability test. The mechanism of surfactant in alkali-activated slag cement was investigated. The results show that:①The adsorbed amount of naphthalene-based and calcium lignosulfonate surfactant on alkali-activated slag phases decreases with the alkali concentration (alkali-equivalent) increases in alkali-activated slag cement system. The adsorbed amount of surfactants decreases as the modulus of water glass increase in range of 1.0 to 2.0.②The silica acid radical in water grass affect theζpotential of alkali-activated slag system. The absolute value ofζpotential of water glass-activated slag system is higher than the that of NaOH-activated slag system under the same alkali-equivalent. The absolute value and falling speed ofζpotential both increase with the alkali-equivalent increases. The absolute value ofζpotential of NaOH-activated slag cement system is enhanced by adding surfactants into the system. Theζpotential of water glass-activated slag cement system changes little after adding surfactants into the system.③The calcium lignosulfonate, naphthalene-based and C18H29SO3Na surfactant can be existed stably in NaOH system when the alkali-equivalent is 4% but the molecular structure of aminosulfonic-based polycarboxylate superplasticizer are destroyed under the same condition. The function groups of surfactant molecular structure are all destroyed in water glass system when the alkali-equivalent is 4% and the modulus is 1.5 except benzene ring.④The calcium lignosulfonate, naphthalene-based and aminosulfonic-based surfactant improve the fluidity of NaOH-activated slag cement paste. On the contrary, they can not improve the fluidity of water glass-activated slagcement paste.⑤The strength of alkali-activated slag cement is enhanced by adding calcium lignosulfonate, aminosulfonic-based, polycarboxylate and C18H29SO3Na surfactant into NaOH-activated slag system. Naphthalene-based surfactant can decrease the water-binder ratio of cement paste but it also can decrease the strength.⑥The initial and final setting time of alkali-activated slag cement are both delayed after adding calcium lignosulfonate and polycarboxylate surfactant into NaOH-activated slag system. All the five kinds of surfactants almost can not affect the setting time of water glass-activated slag cement system.