Measurement of Workability of Fresh Concrete Using a Mixing Truck.
Measurement of Workability of Fresh Concrete Using a
Mixing Truck.
(1088 K)
Amziane, S.; Ferraris, C. F.; Koehler, E. P.
Journal of Research of the National Institute of
Standards and Technology, Vol. 110, No. 1, 55-66,
January/February 2005.
Keywords:
concretes; mixing; rehometers; rheology; mixer truck;
trucks
Abstract:
The main objective of this study is to evaluate the
workability of fresh portland cement concrete while it
is still in the mixing truck by determining fundamental
rheological parameters (plastic viscosity and yield
stress). Nine concrete mixtures with different values of
yield stress and plastic viscosity were tested in a
concrete truck. The measurements made with the truck
were based on the typical method of determining the flow
behavior in a traditional fluid rheometer; that is, the
shear rate in the mixing truck was swept from high to
low by varying the rotation speed of the drum. The
results of these experiments are discussed and compared
with data provided by the ICAR rheometer, a portable
rheometer designed for measuring concrete rheology. The
test results indicate that the mixing truck equipment is
sufficiently sensitive to detect differences in yield
stress, slump, and plastic viscosity. However, the
plastic viscosity determined by the truck measurement
did not correlate with plastic viscosity as measured by
the ICAR rheometer, while the yield stress determined by
the truck measurement did correlate well with the
measured slump and the ICAR rheometer results.
Suggestions are given on how to improve the mixing truck
for better use as a
rheometer.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899