부산대학교 도서관

In this paper, a suite of three Standard Reference Materials (SRM) for calibration of rotational rheometers that are used to characterize the flow of cement-based materials is described. These SRMs were designed to have rheological properties similar to those of a cement paste, mortar, and concrete but are stable for at least 7 days with no hydration. The SRMs for mortar and for concrete are unique because their certifed values are based largely on computer simulations. Indeed, this is the first time that a computer simulation-based SRM has been certifed at the National Institute of Standards and Technology (NIST). The authors were motivated to use a computational approach for creating these SRMs because physical measurements introduced a variety of flow artifacts, due to rheometer designs, that put the experimental results into question. The use of such SRMs for calibrating different rheometers, which typically provide measurements in terms of torque and rotational rate, will allow the user to obtain results in fundamental units. That is, different rheometers will provide consistent measurements of viscosity versus shear rate. In addition, this approach uses a universal scaling ansatz that allows one to establish a relationship between the viscosity versus shear rate of a paste, mortar, or concrete to each other. Keywords: cement-based materials; computational fluid dynamics; non-Newtonian fluids; rheology; shear rate; smoothed particles dynamics; Standard Reference Materials (SRM); viscosity.
INTRODUCTION Concrete performance is generally specified as the strength or durability of its final hardened state. However, these hardened properties would not be achieved if the concrete were not placed [...]