Concrete Pixels

Concrete when produced requires a certain measure of what we call workability. Until today I doubt if there is really a general agreement on the definition of workability. This is the reason why there are so many methods in measuring it like the slump, flow, vebee, compaction index, etc. Despite it’s many limitation, the slump is the most popular method for centuries and accepted globally in almost every local standard due to its simplicity and ease of use at job sites. A It does not directly measure the work needed to compact the concrete but it gives a reasonable indication of how easily a mix can be placed. The advancement of technology has also advanced the method in measuring workability. The latest of which is by employing the concept of rheology. Rheology refers to the study of flow of matter not only liquids but also soft solids where the flow can not be characterized by a single value of viscosity like concrete. Concrete rheology is the scientific approach to measuring workability and can be used to optimize mixture proportions and to ensure consistent fresh concrete quality.The characterization and control of rheology are especially critical for specialized concretes such as self-consolidating concrete (SCC).
An instrument was developed by the International Center for Aggregates Research (ICAR) - University of Texas at Austin to efficiently measure the workability of concrete. It is a pretty handy instrument with a four blade vane that is inserted into a sample of fresh concrete and rotated at a series of various speeds. The resulting torque acting on the vane at each speed is recorded and used to compute the Bingham model parameters of yield stress and plastic viscosity in fundamental units. The operation of the test is fully automated and can be completed in less than a minute. In addition, this instrument is capable of performing a stress growth test, monitoring workability retention, and characterizing thixotropy. It is also capable of testing concretes with slumps greater than 50 mm and is especially applicable to self-consolidating concrete (SCC). It is ideal for use on almost any jobsites and can even be brought as checked-in luggage on an airplane. Before using this new high-tech method check that it is acceptable by your codes.