Adsorption Behavior Between Clay And Polycarbonxylic Copolymers

Water reducing agent has been considered as the "Liquid Gold" and the pillar part in the concrete, plays a key role and determines the trend of concrete in the future. Among them, polycarboxylic copolymer is such outstanding, it has the advantages that other water reducing agents does not had, such as high reducing rate, good dispersion, large degrees freedom in the molecular structure, green process. But during the actually process, the raw materials quality of concrete can’t be very well guaranteed, the clay inevitably mixes into concrete along with sands and stones, it will decline the strength and work ability of concrete. The main mineral in clay is montmorillonite, kaolinite, illite with strong adsorption ability, they absorbed the water reducing agent, then reduced the use and work performance of concrete.Polycarboxylic copolymer PC2000, montmorillonite and kaolinite from Tianjian Damao Chemical Reagent Factory, their adsorption behavior such as adsorption rate, adsorption capacity, adsorption mechanism, the effect of temperature and pH was investigated, to provide the theory supports for soling the problem of clay.Studies shows that montmorillonite and PC2000reaches an approximate balance3.5hours to4hours after their contact at room temperature, montmorillonite showed strong adsorption capacity, Adsorption between montmorillonite and PC2000is0.409g/g. When the temperature changes from25℃to50℃, the saturated adsorption capacity is rising, continue to change to80℃falling, and when the pH changes from7.1to11.5, the saturated adsorption quantity has been a downward trend. The (001) crystal plane spacing of montmorillonite increased with the increase of adsorption capacity, showed that the poly carboxylic acid water reducing agent molecules inserted into the (001) space of montmorillonite, and the space scale indicated that poly carboxylic acid is water reducing agent can’t completely inserted into the montmorillonite layers, but part of the branched chain or main chain into the (001) crystal plane. Comparing with the Freundlich equation, the Langmuir equation is suitable to simulate the adsorption process, showed that poly carboxylic acid water reducing agent in montmorillonite is allocated on the surface absorption effect and the distribution effects, and the distribution effects is dominant. Kaolin and poly carboxylic acid water reducing agent achieved an approximate balance within4hours to4.5hours. The saturated adsorption capacity between kaolinite and poly carboxylic acid water reducing agent is0.009g/g. When the temperature changes from25℃to60℃, the saturated adsorption amount of rising, continue to change to80℃and fall, when the pH changes from7.1to11.5, the saturated adsorption quantity has been a downward trend. Langmuir equation and Freundlich equation is suitable to simulate the adsorption process of kaolin and poly carboxylic acid, surface adsorption and distribution effect is the dominant factor.The mixed and poly carboxylic acid water reducing agent achieved an approximate balance within4hours, and combination condition shows a higher saturated adsorption capacity than a single component, this may related to "Synergy".