Studies on Rheological Properties of High-Flowable Concrete

Abstract

Self-compacting concrete (SCC) has considerably lower yield stress as compared to the conventional vibrated concrete (CVC) in their fresh condition and this forms one of their primary differences. To place CVC and SCC via pumping, the latter would require a lower pumping pressure to pump and place as it requires lower yield stress in comparison. Pumping is one of the most preferred methods of conveying and placing concrete due to the field requirements of reaching heights and less accessible places. It is obvious that the intensity of pumping pressure might affect the state of fresh properties of concrete, while being pumped and/or placed. Currently, Rheometers are available to measure the fresh properties of pumped concrete under dynamic condition, i.e., while the mixes are being agitated and pumped; similar instruments are not extensively available or used after pumping and placing concrete i.e., when concrete is at rest when supported on a formwork post pumping and placing. It is necessary to study the fresh properties of placement of concrete at rest i.e., under static condition to understand the actual phenomenon under said condition. The current experimental study attempts to determine the fresh properties of concrete under rest i.e., static condition using shear box test. The concrete mixes were proportioned using volume fraction technique and their characteristics were evaluated using both empirical and material science approach.

The results show the uniqueness of the approach for determining the rheological properties of CVC and SCC mixes under static conditions. The study exhibits an interesting finding, which is the invalidation of the use of Bingham model for SCC with a flow value of 800 mm and beyond.