Reinforcement mechanisms of cementation strength at the interface between the casing and the sulpho-aluminate set cement

Sulpho-aluminate cement is a kind of potential cementing material, and its microstructure and cementation strength at the cementing interface have not been figured out. In regard of this, the reinforcement mechanisms of cementation strength at the cementing interface of sulpho-aluminate cement slurry were experimentally studied. The hydration mechanisms of sulpho-aluminate cement slurry were investigated by using the X-ray diffractometer, the cementation strength at the cementing interface of sulpho-aluminate cement slurry were measured by means of the cementation strength test unit, and the microstructure and chemical compositions at the cementing interface were characterized by virtue of scanning electron microscope (SEM) and X-ray energy spectrum analysis. It is shown that the cementation strength between the sulpho-aluminate cement and the casing at the age of 1 d, 3 d and 7 d is 24.3%, 20.1% and 25.3% higher than that of G-grade cement of the same age. The microscopic analysis result indicates that a large amount of Al element (AH₃ gel) accumulates on the surface of the casing, and its high polymerization degree can decrease the porosity at the interface, so as to improve the interface cementing performance of sulpho-aluminate set cement.