Characterization and Utilization of Polystyrene and Polyacrylamide-Graft-Methoxypolyethylene as Cement Admixtures

A series of polystyrene-g-methoxypolyoxyethylene (PS-g-MPOE) was prepared by solution polymerization technique using benzoyl peroxide as an initiator and another series of polyacrylamide-g-methoxypolyoxyethylene (PAM-g-MPOE) was prepared by using potassium persulfate initiator. The prepared grafted copolymers were characterized by infrared (IR), thermogravimetric analysis (TGA) and rheological properties. The results illustrated that the solution of PS-g-MPOE in water behaved as a Newtonian fluid, but the solution of PAM-g-MPOE as pseudoplastic at higher acrylamide ratios. The TGA analysis showed that the thermal stability of PAM-g-MPOE was highest. Some of these polymers were evaluated as cement admixtures. The water of consistency and setting time of the cement pastes premixed with the polymers decreased sharply than those of the blank, i.e., these polymer admixtures can act as superplastisizers and at the same time as accelerators. The combined water and free lime contents as well as compressive strength of the cement pastes premixed with PS-g-MPOE or PAM-g-MPOE were slightly lower than the blank at the early ages up to 7 d, and then became higher during the later hydration ages. Their total porosities are higher during the early ages and lower during the later ages of hydration. The SEM images confirmed that the addition of the organic polymer solutions to the cement powder does not affect the chemical composition of the normal hydration products, but only affects the physical state, shape or morphology and size of crystals of the formed hydrates.