Time-Dependent Variations of Compressive Strength and Small-Strain Stiffness of Sands Grouted with Microfine Cement

Unconfined compressive strength ($q_{\mathrm{ucs}}$) and maximum shear modulus ($G_{\max }$), which are essential properties of grouted sands for quality control and stable design, exhibit a nonlinear behavior with curing time that makes it difficult to estimate the long-term $q_{\mathrm{ucs}}$ and/or $G_{\max }$. This study investigates the applicability of the hyperbolic model to capture the nonlinear development of $q_{\mathrm{ucs}}$ and $G_{\max }$ of grouted sands relative to curing time, with the ultimate goal of estimating the long-term $q_{\mathrm{ucs}}$. Three sands with varying particle sizes were grouted with microfine cement at three different water-to-cement ratios ($\mathrm{W}/\mathrm{C}=1$, 1.5, and 2), after which unconfined compression tests and bender element tests were performed according to curing time. The results of this study demonstrate that the hyperbolic model can effectively capture the time-dependent variations of both $q_{\mathrm{ucs}}$ and $G_{\max }$ of the tested grouted sands. Investigation of the hyperbolic coefficient $k$ of the tested materials reveals that the sand particle size and W/C affect the required curing time for completion of the hydration process, and relatively constant $G_{\max }$ values can be obtained at a relatively earlier curing time compared with $q_{\mathrm{ucs}}$. Finally, the direct relationship between $q_{\mathrm{ucs}}$ and $G_{\max }$ is investigated in this study.