Evaluation of Density-Measurement Methods for Construction Slurries

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Abstract The density of slurries is an important quality-control parameter for many types of geotechnical works, such as slurry trenching, grouting, and bored piling. Although the working range of this parameter has been refined over the years in many standard specifications, surprisingly almost nothing has been done to improve the accuracy of the density-measurement technique. For density testing, almost all of the current standards specify the use of the conventional mud balance, although it has a measurement range far greater than what is actually needed for civil engineering works. To provide a scientific basis for the possible adoption of other measurement tools, this paper compares the performance of four different tools, namely, mud balance, digital density meter, aerometer, and pycnometer. From the results, it was found that the performance of the pycnometer depends on its measurement volume, and that the one with a nominal volume of 2 liters gives the best overall performance (measurement error ≤0.001 g/cm3). The accuracy of the mud balance and the aerometer has been found to be dependent on how they are read (i.e., to the original scale division or with care to a half a division) and also on the specimen. The digital density meter, although having good overall performance, cannot be used to measure fluids containing coarse soil particles because of the small diameter of the internal vibrating U-tube. The findings of this study will find applications in geotechnical works involving the use of slurries or grouts.