The standard slump test was performed according to ASTM C143 and the vertical slump of the concrete was measured. Another measurement widely used for flowable concrete but not a standard is the spread of the concrete, after the slump cone was lifted. The diameter of the concrete spread was measured after the concrete had stopped flowing. The time to reach the maximum spread was not recorded.
The IBB rheometer was developed in Canada. It consists of a cylindrical container holding the concrete, with an H-shaped impeller driven through the concrete in a planetary motion. The speed of the impeller rotation was first increased to maximum rotation rate and then the rotation rate was decreased in six stages with each stage having at least two complete center shaft revolutions. The torque (N·m) generated by the resistance of the concrete specimen to the impeller rotation was recorded at each stage as well as the impeller rotation rate (revolutions per second) measured by the shaft tachometer. The torque versus the impeller rotation rate can be approximated by a linear function, whose slope is related to the plastic viscosity and intercept, at zero rotation rate, is related to the yield stress. As the geometry and flow patterns are too complicated in this rheometer, the values obtained are only proportional to the plastic viscosity and yield stress of the concrete. The unit used are N·m and N·m·s for yield stress and viscosity, respectively.
The BTRHEOM is a parallel plate rheometer, i.e., the concrete is sheared between two plates. The plate at the bottom is stationary and the plate at the top rotates with variable speed similar to the impeller of the IBB rheometer. The torque generated during rotation is recorded while the rotation rate is first increased and then decreased in stages. This is similar to the IBB procedure but does not use identical rates and times. The rheological parameters can be calculated using the Bingham equation applied to the torque and rotation rate data of the decreasing speed portion of the test. Due to the simple geometry of the shearing area, it is possible to calculate the results in fundamental units, i.e. Pa for yield stress and Pa·s for viscosity.
The most commonly used test for SCC is a U-flow device ( Figure 1). This test simulates the flow of concrete through a volume containing reinforcing steel. Other tests exist that operate on the same principle with a different geometry but usually they require a larger amount of concrete than the U-flow. The test is performed by first completely filling in the left chamber with concrete (Figure 1) while the sliding door between the two chambers is closed. The door is then opened and the concrete flows past the rebars into the right chamber. SCC for use in highly congested areas should flow to about the same height in the two chambers. The criterion adopted, in this study, was that if the filling height was more than 70 % of the maximum height possible, the concrete was considered self-compacting. The selection of this percentage is arbitrary and a higher value might be considered more conservative. In the U-flow device used, the maximum height is 285.5 mm, half of 571 mm, the total height. Therefore, a concrete with a filling height of more than 200 mm is considered SCC.
Another test used was the V-flow test. It consists of a funnel with a rectangular cross section. The top dimensions are 495 mm by 75 mm and the bottom opening is 75 mm by 75 mm. The total height is 572 mm with a 150 mm long straight section. The concrete is poured into the funnel with a gate blocking the bottom opening. When the funnel is completely filled, the bottom gate is opened and the time for the concrete to flow out of the funnel is measured. This time is called V-flow time.
A full description of all the tests presented here can be found in reference [2].