Onset of Creation of Residual Strain during the hydration of oil-well cement paste

In this paper, the Creation of Residual Strain during the hydration of cement paste is studied by performing oedometric experiments on class G cement pastes during the six first days of hydration. Various conditions of temperature (between 7 and 30 °C) and pressure (between 0.3 and 45 MPa) are explored. It is found that after a hydration degree of about 18%, mechanical loadings can induce residual strain. This state is reached at a time called critical time for Creation of Residual Strain (CRS). It corresponds to the maximum axial strain rate in an oedometric test or to the maximum rate of wave-velocity evolution versus time recorded in a Ultrasonic Cement Analyzer (UCA) test. The Boundary Nucleation and Growth (BNG) model is used to estimate the critical time for CRS. Within the range of studied temperatures and pressures, the predictive capacity of the BNG model for estimation of the critical time for CRS is demonstrated.