ACI SCC Testing cheat sheet

Slump flow test (ASTM C1611): invert the slump cone on a level base plate, fill in one continuous lift without rodding, strike off, and lift vertically in 3 s; measure the spread of the resulting circular patty as the average of two perpendicular diameters.

Slump flow classification per ACI 237R: SF1 = 20 to 24 in (510 to 610 mm), SF2 = 24 to 26 in (610 to 660 mm), SF3 = 26 to 30 in (660 to 760 mm); higher flow does not by itself mean better filling ability.

T50 is the time for the patty to reach a 20 in (500 mm) diameter during the slump flow test; shorter T50 (commonly 2 to 5 s for SCC) indicates higher flow rate and lower plastic viscosity.

J-ring test (ASTM C1621): place a 12 in (300 mm) diameter, 4 in (100 mm) tall ring with 16 bars of 0.625 in (16 mm) diameter around the slump cone setup; the J-ring flow is the average of two perpendicular diameters of the patty after the concrete passes the bars.

J-ring blocking assessment: passing ability is judged primarily by the difference between slump flow and J-ring flow; a difference of 1 in (25 mm) or less generally indicates adequate passing ability, and larger differences indicate blocking by the bars.

Visual stability index (VSI) per ASTM C1611: assign 0 (highly stable, no bleed), 1 (stable, slight bleed), 2 (unstable, obvious bleed with mortar halo), or 3 (highly unstable, segregation and mortar halo) based on the slump flow patty.

Column segregation test (ASTM C1610): fill a 26 in (660 mm) tall, 8 in (200 mm) diameter pipe in one lift without consolidation, let it stand undisturbed for 15 min, then divide the column into three equal sections and wash each section over a No. 4 (4.75 mm) sieve to determine coarse aggregate mass per section.

Segregation index = (maximum coarse aggregate mass in a section minus minimum coarse aggregate mass in a section) divided by the average coarse aggregate mass of the three sections; lower values indicate better stability, and values are typically reported as a percentage.

In the field, verify SCC is not over-vibrated: vibration can cause segregation and should be limited to the minimum needed to release entrapped air; SCC should be placed continuously so it flows under its own weight without mechanical spreading.

V-funnel test: fill the V-shaped funnel with about 0.17 ft³ (5 L) of concrete, strike off, open the gate, and record the time for the concrete to flow out; typical SCC values are about 6 to 12 s, with longer times indicating higher viscosity and lower flowability.

L-box test: fill a vertical hopper and horizontal channel separated by vertical reinforcing bars, then lift the gate and record the time to reach 16 in (400 mm) and the heights H1 (at the gate end) and H2 (at the far end); blocking ratio = H2/H1, with values ≥0.8 generally indicating acceptable passing ability.

Orimet test: measure the time for concrete to flow through a 3.1 in (80 mm) diameter orifice at the base of a vertical pipe; it is a rapid indicator of filling ability and flow rate, similar in concept to the V-funnel.

U-box test: fill one side of a U-shaped box containing vertical reinforcing bars, then open the gate and measure the height difference between the two sides; a smaller height difference indicates better filling and passing ability.

Sieve segregation resistance test (ASTM C1610 related): place a sample of SCC on a No. 4 (4.75 mm) sieve, allow mortar to drain for 2 min, and compute the percentage of mortar passing the sieve; higher percentages indicate greater tendency to segregate.

Mixing and conditioning: SCC test specimens should be sampled per ASTM C172 and tested at a consistent age and temperature; test methods are sensitive to rest time, so perform each fresh test promptly after mixing and do not retemper.

For hardened properties, cast specimens without mechanical consolidation per ASTM C192 practice for SCC; SCC typically develops high early strength and low permeability, and compressive strength is evaluated per ASTM C39.

Trial batch acceptance: compare slump flow, T50, J-ring, V-funnel, and segregation results against project-specified ranges before accepting a mixture; no single test fully characterizes SCC, so multiple tests are combined.

Laboratory temperature and moisture: perform fresh SCC tests at a controlled ambient temperature (commonly 68 to 73 °F / 20 to 23 °C) and record concrete temperature, since flow and viscosity results are temperature sensitive.