Effects of β-cyclodextrin side chains on the dispersing and retarding properties of polycarboxylate superplasticizers

摘要

A modified polycarboxylate (MPC) superplasticizer was synthesized by the copolymerization of acrylic acid, methallyl sulfonic acid, allyl poly(ethylene glycol)s, and β-cyclodextrin (β-CD) grafted maleic anhydride. The molecular structure of the MPC was characterized by Fourier transform infrared spectroscopy and gel permeation chromatography. The effects of the content of β-CD on the application performance of MPC were investigated with measurements of the cement paste fluidity, setting time, amount of adsorption of MPC on the cement particles, and Χ potentials of the cement particles and differential scanning calorimetry-thermogravimetric analysis of different hydration ages of the cement pastes. The results indicate that the initial fluidities and setting times of the cement pastes increased with increasing number of β-CD side chains. The dispersion capacity of MPC on the cement particles mainly came from a steric hindrance effect and an air-entraining effect of the β-CD side chains. The better retarding performance of MPC was attributed to the solvation water film formed by the polyoxyethylene side chains and chelates formed by -OH groups on the β-CD structure combined with Ca ~(2+) ions on the surface of the cement particles.