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Open AccessArticle

Estimation of Viscosity and Yield Stress of Cement Grouts at True Ground Temperatures Based on the Flow Spread Test

by Zhipeng Xu 1,2,*, Yichen Miao 3, Haikuan Wu 1,2, Xun Yuan 3 and Changwu Liu 1,2,*
1
College of Water Resource and Hydropower, Sichuan University, Chengdu 610065, China
2
State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu 610065, China
3
Institute for Disaster Management and Reconstruction, Sichuan University-The Hong Kong Polytechnic University, Chengdu 610207, China
*
Authors to whom correspondence should be addressed.
Materials 2020, 13(13), 2939; https://doi.org/10.3390/ma13132939
Received: 2 June 2020 / Revised: 21 June 2020 / Accepted: 30 June 2020 / Published: 30 June 2020
(This article belongs to the Collection Concrete and Construction Materials)
The rheology of cement grouts often plays a crucial role in the success of rock grouting. In practice, the rheological parameters should be timely adjusted according to the evolution of grouting pressure, flow rate and injection time. However, obtaining the magnitude of rheological parameters is not easy to achieve under site conditions. More importantly, the ground temperature in deep rock masses is elevated higher than that on the surface or under room conditions, which has been demonstrated to strongly influence the rheological properties of grouts. Reasonable understanding and control of the rheological behavior of cement grouts at true ground temperatures is very important to the quality of grouting. This paper aims to propose a simplified method to approximately estimate the initial yield stress and viscosity of cement grouts for rock grouting under elevated ground temperature that actually exists in deep rock masses, on the basis of the flow spread test. The temperature investigated was controlled between 12 °C and 45 °C to simulate the true ground temperature in rock masses with a maximum depth of 1500 m below the surface. Taking the influences of elevated temperatures into account, a temperature-based model for estimating the initial viscosity of cement grout was successfully developed on the basis of Liu’s model and the results of the flow spread test. However, the yield stress failed to be estimated by the Lapasin model due to the absence of plastic behavior of cement grouts. In contrast, yield stress can be linearly correlated to the measured relative flow area. In this work, it was also found that the dependence of yield stress of cement grouts on relative flow area is a strongly exponential law. The temperature dependence of the viscosity of water was accounted for in both estimations of viscosity and yield stress of grouts. Significantly, it was found that the packing density of cement is dependent on the grout temperature, especially when the temperature is up to 45 °C. The proposed method in this work offers an alternative solution for technicians to reasonably control the rheological properties in the increasing applications of deep rock grouting. View Full-Text
Keywords: viscosity; yield stress; cement grout; flow spread test; temperature; deep rock grouting viscosity; yield stress; cement grout; flow spread test; temperature; deep rock grouting
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MDPI and ACS Style

Xu, Z.; Miao, Y.; Wu, H.; Yuan, X.; Liu, C. Estimation of Viscosity and Yield Stress of Cement Grouts at True Ground Temperatures Based on the Flow Spread Test. Materials 2020, 13, 2939.

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