Time-dependent characteristics of quick-setting slurry rheological parameters with extremely high temperature: Experimental study

The increasing number of deep-buried tunnel projects has made high-temperature water inrush disasters a severe challenge for tunnel construction. Grouting has been proven to be one of the most effective measures against such disasters, with quick-setting slurry being the most commonly used grouting material. Nevertheless, time-dependent characteristics of quick-setting slurry rheological parameters under high temperatures remain insufficiently understood, which affects the prediction of the grouting effect. To fill this knowledge gap, this study proposed a fixed-shear rate rheological testing method, which suits the extremely short phase transition duration of quick-setting slurry under high-temperature conditions. Taking the cement-sodium silicate slurry (C-S slurry) as a typical quick-setting slurry, the relationships between slurry shear stress and shear rate under different temperatures and slurry proportions were studied. The results revealed that the slurry flow pattern remained that of a Bingham fluid and neither temperature nor slurry proportions could alter this flow behavior. Nevertheless, the fluid–solid phase transition process could be significantly affected by the temperature and slurry proportion. Increases in temperature and the cement to sodium silicate volume ratio (c/s ratio) could shorten the slurry phase transition duration by up to 60 % and 89 % respectively. Conversely, an increase in the water to cement ratio (w/c ratio) would extend the phase transition time by a maximum of 25 %. In addition, the peak yield stress and viscosity of the slurry dropped with the increase in temperature and w/c ratio, while with the decrease in c/s ratio. Compared to 10 °C, the peak yield stress and viscosity decreased by 51 % and 37 % respectively at 90 °C. At a w/c ratio of 1.6, the peak yield stress and viscosity dropped by 47 % and 67 % relative to 0.8. With a c/s ratio of 1, the peak yield stress and viscosity decreased by only 18 % and 28 % compared to 3. The effect of temperature and the w/c ratio on peak yield stress and viscosity of the slurry was more pronounced than the c/s ratio. Time variation curves of slurry yield stress and viscosity during the fluid–solid phase transition process conformed to power functions. Constitutive equations of C-S slurry with different temperatures and proportions during the whole phase-transition process were established, which are expected to provide theoretical basis for grouting control and water disaster treatment in deep buried tunnels.