Concrete is a complex material formed mainly by cement paste and aggregates. Currently, to measure the flow properties of concrete, semi-empirical measurements are commonly used (e.g., slump cone). In this project, the goal is to provide industry with tools, both experimental and simulation based, to predict the rheological properties of concrete based on sound material science, instead of semi-empirical methods. The NIST approach to develop new measurement science tools has been to use a multiscale model, where cement paste is the fluid for mortar and subsequently mortar is the medium for concrete. Hence, the knowledge of the cement paste behavior would be the input for a computerized simulation to predict concrete rheological properties. NIST has already developed some tools to measure paste and mortar, Standard Reference Materials (SRMs) to calibrate rotational rheometers, and a grout pumping station to validate the predictions. Thus, this project would include improving prediction of the flowability in a pipe, placement of concrete, and finishability. Further test methods to measure the rheological properties at the construction site or in the laboratory, both as quality control or validation of the model, will be developed. These new test methods could he submitted to ASTM for adoption as a new standard.

References

Ferraris CF, Martys NS: Chapter 4-Concrete Rheometers, in Understanding the Rheology of Concrete. Edited by Nicolas Roussel, Oxford: Woodhead Publishing, 20l2

Ferraris CF, et al: Development of a Reference Material for the Calibration of Cement Paste Rheometers, ASTM-Advances in Civil Engineering Materials (2)1: 2013

Martys NS, et al: Rheologica Acta 49: 1059, 2010