The science of rheology is increasingly used to describe the properties of fresh cement paste. Compared to standard workability tests, rheological properties allow for more fundamental investigation, more precise phenomenological description of flow properties and serve as input for numerical simulations. Standard commercially available rheometers are typically used to perform those measurements. However, the results of the measurement depend on the geometry, testing procedure and a number of potential artefacts. This technical letter describes the most common techniques and procedures used to assess the rheological properties of cement paste, as well as challenges during measurements and actions to counter these challenges.

No abstract

Different methods for measuring particle size distribution (PSD) and specific surface area of crushed aggregate fines (≤ 250 µm), produced by high-speed vertical shaft impact (VSI) crushing of rock types from different quarries in Norway, have been investigated. Among all the methods studied, X-ray sedimentation is preferred because it has adequate resolution and requires fewer and more reliable input parameters. This combination makes it suitable for practical applications at hard rock quarries. X-ray microcomputed tomography (µCT) combined with spherical harmonic analysis was applied to estimate the actual error introduced when PSD measurements were used to calculate the specific surface area of the VSI crushed rock fines. The µCT results, to the limit of their resolution, show that the error in the calculated surface area caused by assuming spherical particles (a common assumption in PSD measurements) is of unexpectedly similar magnitude (-20 % to-30 %) over the entire investigated particle size range, which was approximately 3 µm to 200 µm. This finding is important, becauses it simplifies relative surface area determination and is thought to be quite general, since the crushed aggregate fines investigated were produced from 10 rock types that had a wide range of mineralogies.