For a large pour with multiple suppliers, what is the purpose of representative cylinder sampling?

• A. To limit the number of samples.
• B. To sample at the start only.
• C. To sample only after mixing at the end.
• D. To ensure samples reflect the overall batch across suppliers.

Answer: (D)

When multiple suppliers contribute to a single large pour, the sample must represent the entire batch, not just a portion. Concrete from different trucks can vary slightly in slump, air content, temperature, and strength. By taking cylinder samples that reflect material from all sources in proportion to their share of the pour and combining them into a representative composite sample, you ensure the test results apply to what was actually placed. This makes your strength and quality checks meaningful for the whole pour and helps catch issues that could be missed if you only sampled from one supplier or only at a certain stage.

Limiting the number of samples or sampling only at the start or only after mixing at the end would fail to capture the variability across the entire batch, so the results wouldn’t reliably represent what was placed.