Cement stress and microstructure evolution during curing in semi-rigid high-pressure environments

• Published in: Cement and concrete research Vol. 149; p. 106555
• Main Authors: Meng, Meng, Frash, Luke P., William Carey, J., Li, Wenfeng, Welch, Nathan J., Zhang, Weicheng
• Format: Journal Article
• Language: English
• Published: Elmsford Elsevier Ltd 01.11.2021; Elsevier BV; Elsevier
• Subjects: 02 PETROLEUM; Cement; Cement hydration; Cements; Curing; Foundations; Initial stress; Initial stresses; Microstructure; Porous media; Slurries; Steel pipes; Steel structures; Stress state; Well drilling; Wells; Zonal isolation; Initial stress; Foundations; Zonal isolation; Cement hydration; Wells
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/j.cemconres.2021.106555

The process of cement slurry curing into a solid has a direct effect on the initial state of stress in a composite concrete and steel structure. Failure models for critical infrastructure and wellbores could benefit from measurements of this initial stress because it greatly influences structural performance. Here, we present measurements of the initial stress state (total stress, effective stress, and pore pressure) of multiple cement formulations cured under a high-pressure of 40 MPa within a semi-rigid steel pipe. Our results show that cements cured in this restrained environment exhibit dense microstructures with low permeability (nano-Darcy), develop an anisotropic stress state greater than zero and less than the curing pressure, and undergo a staged curing process where hydration and mechanical behaviors evolve from a slurry into a pre-stressed porous medium. Both drained and undrained scenarios were investigated, revealing a feedback from the semi-rigid boundary towards improved cement performance.