Effect of SRA and active MgO expansive agent on volume deformation and mechanical properties of Portland cement composites

The volume shrinkage of Portland cement during the hydration process will lead to micro cracks in the cement sheath and affect the cementing quality. In order to further alleviate the volume shrinkage of Portland cement, the shrinkage reducing agent (SRA) and a variety of different active MgO expansive agent (MEA) were added to the cement slurry, and the effects of the two on the hydration characteristics, volume deformation, mechanical properties, and phase transformation of cement were studied. The results showed that the combined use of SRA and active MEA can effectively reduce the volume shrinkage of cement slurry under sealing conditions and increase the free expansion rate of cement. The volume shrinkage of the combined cement slurry of SRA and medium active MEA (MgO-M) is only 1.73% in 168 h, and the free expansion rate is 0.15% in 90 days. SRA and active MEA have a synergistic effect in compensating the volume shrinkage of cement, the addition of SRA delays the hydration of MEA, which can avoid the ineffective expansion caused by excessive hydration of highly active MEA, and help MEA play a more effective expansion role in the strength development stage of cement stone. Studied the effects of SRA and activity MEA on volume deformation, mechanical properties, phase change and microstructure of oil well cement.The combined application of SRA and active MEA can significantly reduce the shrinkage of cement slurry and increase the free expansion.Explained the synergistic expansion mechanism of SRA and active MEA.

Automated summary

The study examined the effects of a shrinkage reducing agent (SRA) and various active MgO expansive agents (MEA) on the hydration characteristics, volume deformation, mechanical properties, and phase transformation of cement. The results showed that the combined use of SRA and active MEA effectively reduced volume shrinkage and increased free expansion of the cement slurry.