Which sequence correctly describes the steps for slump testing the delivered concrete?

Which sequence correctly describes the steps for slump testing the delivered concrete?

• A. Collect a sample, fill the slump cone in lifts, compact each layer, strike off the top, lift the cone and measure the slump.
• B. Collect a sample, strike off the top before filling the slump cone, then compact each layer and measure.
• C. Fill the slump cone with concrete, compact each layer, then collect a sample and measure the slump.
• D. Collect a sample, fill the slump cone in lifts, compact only the bottom layer, strike off the top, and measure slump.

Answer: (A)

The test measures concrete’s workability by how much its height changes when the slump cone is removed, so the steps must establish a consistent starting point and uniform compaction before removing the mold. Start by taking a representative sample and placing the slump cone on a flat, non-absorbent surface. Fill the cone in three equal lifts, ensuring each layer is firmly compacted to eliminate air pockets. After the cone is fully filled and each layer compacted, strike off the excess concrete level with a straight edge to create a clean, level top. Then lift the cone away smoothly and vertically, without twisting, and measure how far the concrete subsides—the slump. This sequence yields a reliable measure of workability because the three-layer fill and per-layer compaction produce a uniform sample, the strike-off provides a defined starting height, and lifting the cone without disturbance gives an accurate height change. The other options mix up the order or omit important steps: striking off before filling doesn’t establish the correct initial surface, measuring before lifting ignores the actual slump, and compacting only the bottom layer fails to produce a representative sample.

The test measures concrete’s workability by how much its height changes when the slump cone is removed, so the steps must establish a consistent starting point and uniform compaction before removing the mold. Start by taking a representative sample and placing the slump cone on a flat, non-absorbent surface. Fill the cone in three equal lifts, ensuring each layer is firmly compacted to eliminate air pockets. After the cone is fully filled and each layer compacted, strike off the excess concrete level with a straight edge to create a clean, level top. Then lift the cone away smoothly and vertically, without twisting, and measure how far the concrete subsides—the slump. This sequence yields a reliable measure of workability because the three-layer fill and per-layer compaction produce a uniform sample, the strike-off provides a defined starting height, and lifting the cone without disturbance gives an accurate height change.

The other options mix up the order or omit important steps: striking off before filling doesn’t establish the correct initial surface, measuring before lifting ignores the actual slump, and compacting only the bottom layer fails to produce a representative sample.