Relating fresh concrete viscosity measurements from different rheometers

Abstract

Concrete rheological properties need to be properly measured and predicted in order to characterize the workability of fresh concrete, including special concretes such as self-consolidating concrete (SCC). It was shown by a round-robin test held in 2000 [1,2] that different rheometer designs gave different values of viscosity for the same concrete. While empirical correlation between different rheometers was possible, for a procedure that is supposed to “scientifically” improve on the empirical slump tests, this situation is unsatisfactory. To remedy this situation, a new interpretation of the data was developed. In this paper, it is shown that all instruments tested could be directly and quantitatively compared in terms of relative plastic viscosity instead of the plastic viscosity alone. This should eventually allow the measurements from various rheometer designs to be directly calibrated against known standards of plastic viscosity, putting concrete rheometry and concrete workability on a sounder materials science basis.

Towards a prediction of superplasticized concrete rheology

“…This ought to be the case for plastic viscosity. In fact, Ferraris and Martys [12] have recently shown that the plastic viscosity of concrete normalised by the plastic viscosity of its corresponding mortar, tends to follow a master curve which is well matched by their simulation (Fig. 3).…”

The virtual cement and concrete testing laboratory consortium:

“…Plots of relative viscosity versus volume fraction of coarse aggregate were shown to be in reasonably good agreement across laboratories using different rheometer geometries, as shown in Figure 4. These results lend support to the claim that the influences of geometry and experimental procedure can be scaled out of the measurements to some extent, yielding truer measurements of the actual rheological properties of the material, by using relative viscosity instead of plastic viscosity [10]. The influence of air content on the flow of concrete was also investigated, and Fig.…”

Parallel-plate Rheometer Calibration Using Oil and Computer Simulation

“…Clearly, great care must be taken when interpreting experimental results on rheology of fresh cementitious materials and also when comparing results derived from different rheometers (Ferraris et al 2003). In this paper all the experimental work and the simulation was performed using an oil and not a suspension.…”