Non-contact viscosity detection for cement slurry using laser scanning of wave motion under rod impact

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Concrete workability was typically assessed using slump tests and viscometers, which involved contact-based measurements and required sampling, making them unsuitable for online measurements. This study proposed a non-contact inspecting approach by utilizing a laser profiler to scan the mixture surface height changes at high speed and high resolution when the mixture was impacted by a free-fall rod. The energy transfer efficiency was defined to analyze the energy transferred from the rod kinetic energy to the mixture waving energy, and the mechanism between the material hydration and the surface dynamic response was revealed. The maximum wave peaks, waveform areas, and energy transfer efficiencies were extracted as critical features and established a robust correlation with the mixture viscosity with R2 of 0.945, 0.919, and 0.949 correlation with the viscosity, respectively, proving that the proposed approach can be utilized in the in-line liquid material inspection. This study demonstrated the laser scanning method as a simple and effective approach, providing the possibility of non-contact detection to characterize the rheological properties by analyzing the surface fluctuations.