Abstract:
The purpose of this experimental work is to determine the domain of the Bingham constants within which a concrete mix possesses self-compactability. Flow characteristics or the rheological characteristics of concrete were expressed by using the Bingham model. Yield shear stress and the plastic viscosity are the two flow properties included in the Bingham model. A range of the combinations of yield shear stress and plastic viscosity was identified within which the concrete is likely to be self-compactable.
To determine the self-compactability of a concrete three index properties were determined by experiments. Those three properties are the filling ability, passing ability and the segregation resistance. To measure the filling ability, slump flow by Abram’s cone, T50cm slump flow time and V funnel test were used. To measure the passing ability, J ring test was used. V funnel at T5min test was used to test the resistance to segregation. Self-compactability was judged by comparing the results with the acceptable regions given in the EFNARC publications. Yield shear stress and the plastic viscosity were calculated by using the rotational speed and the applied torque on the concrete which were measured by a coaxial type cohesiometer.
The analysis of data by statistical procedures led to the charts showing variations of the workability indices with the water powder ratio and the superplasticizer dosage for different water cement ratios. Those charts are useful when proportioning self-compacting concrete mixes.
