How is the slump test performed and what constitutes a valid result?

• A. Fill cone in two lifts, rodding each, strike off, measure slump; must exceed design range.
• B. Follow ASTM C143: fill cone in three lifts, rodding each lift, strike off, lift and remove cone, measure slump; result must meet project-design range.
• C. Pour slump directly on ground and estimate visually.
• D. Use oven-dried sample to determine slump.

Answer: (B)

The key idea is how to gauge the workability of fresh concrete using the standard slump test. This test follows ASTM C143, which requires filling the slump cone in three equal lifts, rodding each lift to consolidate, striking off the top flat, then lifting the cone straight up and letting the concrete slump. The slump value is the vertical distance the concrete subsides from the original top of the mold, measured after the cone is removed. This measured slump must fall within the project’s specified design range to be considered valid. If the result is outside that range, the mix or proportioning needs adjustment and the test repeated.

Why the other options don’t fit: the method uses three lifts with proper rodding and removal of the cone, not two lifts or any other sequence; the test uses fresh concrete, not material poured directly on the ground; and you don’t assess slump with an oven-dried sample, since that would not reflect workability of fresh concrete.