Yield stress of cement grouts

• Published in: Tunnelling and underground space technology 2017-01, Vol.61, p.50-60
• Main Authors: Rahman, Mashuqur, Wiklund, Johan, Kotzé, Reinhardt, Håkansson, Ulf
• Format: Article
• Language: English
• Subjects: Cement grout; Cement grouts; Cements; Design standards; Dielectric losses; Direct measurement; Elasticity; Flow velocity; Grout; Grouting; Grouting designs; In-line measurements; In-line rheology; Measurement techniques; Mortar; pH effects; Pressure differences; Prestressed materials; Pulsed Ultrasound Velocimetry + Pressure Difference; Rheological properties; Rheology; Rheometers; Shear rate; Thixotropy; Ultrasonic applications; Ultrasonic testing; Ultrasound; Velocity profiles; Yield strength; Yield stress
• ISSN: 0886-7798; 1878-4364; 1878-4364
• DOI: 10.1016/j.tust.2016.09.009

•Two ranges of yield stress, i.e., static and dynamic yield stress was measured.•The static and dynamic yield stress should be used as the design input for grouting.•The Flow Viz industrial rheometer can perform direct measurement of yield stress.•The change of viscosity is abrupt just below and above the yield stress. The rheology of cement grout is complex due to its thixotropic nature and the presence of a yield stress. Despite the importance of the yield stress for grouting design, no standard methods are yet available to determine the yield stress. Most common methods are based on using conventional rheometers, but the results are subjective due to the measurement techniques, applied shear history and hydration. In this work, measurement of the yield stress of cement grout was performed with different measurement techniques using a conventional rheometer. In addition, in-line measurements using an ultrasound based technique were made in order to visualize the flow profile and perform a direct measurement of the yield stress. Two ranges of yield stress, static and dynamic yield stress, were measured. These results should be used for design purposes depending on the prevailing shear rate. The ultrasound based Flow Viz industrial rheometer was found capable of performing direct in-line measurement of the yield stress and providing a detailed visualization of the velocity profile of cement grout.