The Adsorption Characteristics Of Polycarboxylate Superplasticizer To The Hydration And Nonhydratable System

Polycarboxylate superplasticizer has been widely used as an important direction for the development of the concrete admixtures in modern concrete projects because of the high water reducing ration and excellent slump performance and so on. It has become increasingly prominent that the compatibility problems of the polycarboxylate superplasticizer with cement, fly ash and slag with the growth in the number of industrial waste and environmental resources. Most of previous studies of polycarboxylate superplasticizer to cement and fly ash or mineral powder mixed gel system in the research.However, the research on adsorption characteristics of particle surface behavior of the polycarboxylate superplasticizer with a single component of fly ash and mineral powder research was less. This article selected the base of cement, fly ash and slag, to research the influence of adsorption behavior and the fluidity of paste of the polycarboxylate superplasticizer with cement, fly ash and slag particle surface. The main research results were as follows:The fluidity of paste of polycarboxylate superplasticizer with the base cement, fly ash and slag was studied. Test results showed that with the increasing of the dosage of polycarboxylate superplasticizer, the increasing of the initial fluidity of base cement, fly ash and slag. When the content reached a certain value, the fluidity was stable. However it was higher than the certain value, it could reduce the fluidity. Meanwhile the fluidity of the citric acid to the three powder paste was also studied. The results showed that the initial fluidity of paste could increase, in the contrary, the initial fluidity of paste could reduce.The adsorption behavior of powder particle surface of polycarboxylate superplasticizer to the base cement, fly ash and slag were studied. The results showed that the adsorption behavior on base cement, fly ash and slag particles could be described with Langmuir monolayer adsorption. The sequence of adsorptive amount was as follows: base cement >slag> fly ash.The effect of competition adsorption between polycarboxylate superplasticizer and retarder citrate in the powder particle surface was also studied. The results showed that the addition of an excess of citric acid, resulted in the decrease of polycarboxylate superplasticizer adsorption capacity in the powder particle surface.The zeta potential of cement paste was determined through zeta potentiometer. The results showed that the polycarboxylate superplasticizer also has electrostatic repulsion. Compare to the naphthalene superplasticizer, the zeta potential of polycarboxylate superplasticizer was lower.XPS of polycarboxylate superplasticizer with powder paste was researched. Results showed that the addition the polycarboxylate superplasticizer enhanced the peak of C, and reduced the O and Ca peak, and decreased slightly the peak of Si. By calculating the thickness of adsorption layer of the Si on the surface of the powder particles, it showed the thickness of adsorption layer of the cement was largest.This paper aimed at studying the hydrated cement paste and the nonhydrated fly ash and slag paste and the difference of the fluidity of the paste and adsorption of the polycarboxylate superplasticizer to the system of hydrated and nonhydrated, which discussed the interaction mechanism of collaborative applications of polycarboxylate superplasticizer and cement, fly ash and slag.