Amphoteric ion polymer as fluid loss additive for phosphoaluminate cement in the presence of sodium hexametaphosphate

The fluid loss of modified aluminate phosphate cement system with excellent CO2 resistant ability cannot meet the demand of cementing engineering and the conventional fluid loss additive lose effectiveness in this cement system. The aim of this paper is to reveal the failure mechanisms of the conventional fluid loss additive and develop one kind of amphoteric ion polymer to control the fluid loss. Results showed that massive of sodium hexametaphosphate exists in cement system limits the hydration and expansive degree of hydrophilic group of fluid loss additive and succeeds in the competition with fluid loss additive for adsorbing on the surface of cement particle. Using 2-acrylamido-2-methyl propane sulfonic acid, acrylamide, diallyl dimethyl ammonium chloride, and itaconic acid, a new fluid loss additive which has excellent ability to control fluid loss is synthesized by free radical aqueous solution copolymerization. The reducing fluid loss function of this kind of fluid loss additive is achieved by the cationic groups adsorbing on the surface of cement particle and anionic groups absorbing water to achieve hydration expansion to plug the flow passages between the cement particles. However, the dosage of this kind of fluid loss additive is limited by the negative retarding effect.