, , , , Alex Olivas
The calibration of rheometers to determine the rheological properties of cement based materials ranging from cement paste to concrete cannot be done using standard oils as they are cost prohibitive and do not possess sufficient granularity to test slip phenomena at the fluid wall interface. From American Concrete Institute Committee 238 discussions and two international testing campaigns, it was clear that there was a need for a reference material specifically designed for such granular materials. A newly developed series of reference materials, composed of corn syrup solution, fine limestone powder and glass beads, is presented here. Glass beads of 1 mm and 10 mm represent the sand and coarse aggregates respectively, while the mixture of corn syrup solution and limestone represents the paste. These systems simulating cement paste, mortar and concrete were tested using both rheological measurements and modelling. The synergy between experimental and modeling allowed for the elucidation of an effective slippage phenomenon near the moving surface, and suggested possibilities to reduce it. This paper explores what kind of measurements would be most suitable for the development of the reference materials as well as the results obtained using various rheometer geometries, such as parallel plate, coaxial, vane and double spiral geometries. A critical analysis on the measurement techniques is presented.
Rheology, Rheometers, Reference Materials