Henry G. Russell, Henry G. Russell, Inc.
Self-consolidating concrete (SCC) must have the ability to flow under its own weight, to pass reinforcing bars or other obstacles without segregation, and not segregate during or after casting. The following ASTM standard test methods have been developed to address these fresh concrete properties.
ASTM C1611—Slump Flow of Self-Consolidating Concrete
This test is performed in a similar manner and with similar equipment as the conventional slump test—ASTM C143. The slump cone can be either used the same way up or inverted. A sample of freshly mixed concrete is placed in the cone in one lift without tamping or vibration. The mold is lifted and the concrete allowed to spread. After spreading ceases, two orthogonal diameters of the concrete patty are measured. The slump flow is the average of the two diameters.
The slump flow test allows a comparison of the lateral flow and filling potential of different SCC mixtures. A common range of slump flow for SCC is 18 to 30 in. (450 to 750 mm). The slump flow test can be used in production to assess the consistency of SCC. According to ACI 237R-07, the slump flow should not differ by more than 2 in. (50 mm) from batch to batch.
A nonmandatory appendix of ASTM C1611 provides a procedure for a relative measurement of flow rate, viscosity, and stability. The flow rate is determined by measuring the time it takes for the outer edge of the concrete to reach a diameter of 20 in. (500 mm). The flow rate is influenced by the concrete’s viscosity. The stability can be observed by visually examining the concrete patty for evidence of segregation.
ASTM C1621—Passing Ability of Self-Consolidating Concrete by J-Ring
This test method provides a procedure to determine the passing ability of concrete by using a J-Ring in combination with the ASTM C1611 slump flow test. The J-Ring is placed outside the slump cone so that the concrete flows through the legs of the ring when the cone is lifted. The slump flow with and without the J-Ring is measured. A difference of less than 1 in. (25 mm) indicates good passing ability. A difference greater than 2 in. (50 mm) indicates poor passing ability. The test method is suitable for use in the laboratory and in the field.
ASTM C1610—Static Segregation for Self-Consolidating Concrete Using Column Technique
In the test method, a sample of freshly mixed concrete is placed in a cylindrical mold without tamping or vibration. After 15 minutes, the mold is separated into three sections representing the top, middle, and bottom of the cylinder. Each section is removed individually and the concrete in the top and bottom sections washed over a No. 4 (4.75 mm) sieve. The retained aggregate from each section is weighed and the static segregation calculated as the difference between the bottom and top sections divided by the average weight. The test method is a laboratory procedure to determine the potential static segregation. An SCC mixture is generally considered to be acceptable if the percent segregation is less than 10% (ACI 237R-07).
Further information
ACI 237R-07, Self-Consolidating Concrete, American Concrete Institute, Farmington Hills, MI, 2007, 30 pp.