Influence Of The Surface Properties Of Cement Material On The Adsorption Of Superplasticizers

Superplasticizer is an essential component of manufacturing high performance concrete materials, and it has become the fifth important component in concrete. At present, people usually adopt surface zeta potential of particles, adsorption and thickness of adsorption layer to characterize the effects of superplasticizer on cement. But the research hasn’t been done on the properties of the powders before mixing. Surface energy is one of the important parameters of powder material performance. Therefore, studying the effect of powder surface property on the absorption of superplasticizer is of great significance.By measuring the surface energy of cement and fly ash powders, surface zeta potential of particle and superplasticizer adsorption within different concentration solution of polycarboxylate type and naphthalene superplasticizer, the relationship between surface energy, zeta potential and superplasticizer adsorption was discussed.From the present study the following conclusions can be drawn:1.The fineness of cement powder A, B, C, in order: cement A > cement B > cement C. With the increase of powder fineness, the dynamic contact angle between deionized water and the thin layer of cement powder decreased,and the hydrophilic enhancement. The surface energy of the cement powder A, B and C were 55.5427mN·m-1、53.3935 mN·m-1、50.5843mN·m-1, respectively. The surface energy of the fly ash powder FA and FB were 42.9175mN·m-1and 36.8512mN·m-1. As to powder particles, the more finenesss, the bigger the surface energy. The cement powder had stronger hydrophilic than fly ash and the surface energy of cement powders is three times bigger than that of fly ash with the same particle size distribution.2. In the deionized water solution, surface zeta potential of cement particle was changed from positive to negative as the hydration time extension. However, zeta potential of fly ash was negative and almost didn’t change over time.3. In the same superplasticizer solution, cement particle surface zeta potential tends to increase with concentration added and decrease over time. The cement particle surface zeta potential in and naphthalene superplasticizer solution was larger than in polycarboxylate type superplasticizer. The adsorption of superplasticizer at cement was increase with the extension of time. Compared with polycarboxylate type superplasticizer, the cement showed higher adsorption in naphthalene superplasticizer solution. It is related to functional groups contained in superplasticizer molecule and the molecular structure. For the same type and concentration of superplasticizer solution, the adsorption from low to high followed by cement A, B and C, that is the higher surface energy, the larger adsorption. Fly ash and cement showed a similar rule, but the zeta potential and the adsorption were reduced to various degrees.4. In different type of superplasticizer solution, absolute value of cement and fly ash particle surface zeta potential and adsorption capacity were increased as the initial concentration of the superplasticizer increasing, and increasing with the increase of surface energy, almost the linear relationship.