Adsorption capacity and mechanism of citric acid-modified chitosan on the cement particle surface

Abstract

In this paper, citric acid-modified chitosan (CAMC) was added to cement slurry and its adsorption and hydration regulation mechanism on cement particles was studied. The rheological properties, agglomeration properties, and adsorption properties were characterized by different testing techniques. The effect of CAMC on the evolution of C-S-H gel and aluminum hydrate was further studied by the NMR technique. The results show that the negatively charged CAMC will adsorb on the surface of cement and agglomerate cement particles. In addition to being adsorbed on the positively charged aluminate phase surface under the electrostatic effect, CAMC was also adsorbed on the negatively charged silicate phase through complexation between carboxyl groups and calcium ions. The formation of complexes on the surface of the silicate phase hinders the hydration of calcium silicate (C3S).CAMC significantly reduced the hydration rate of early cement, hindering the nucleation of C-S-H and ettringite (AFt).