Compressive Strength Comparison must be performed within what timeframe after placement?

• A. Within 24 hours post-placement
• B. Within 7 days post-placement
• C. At 28 days
• D. Before placement

Answer: (A)

Early-age strength verification is done soon after concrete placement to decide if it has reached the required strength before proceeding with next steps like form removal or allowing traffic. Testing the compressive strength within 24 hours after placement gives rapid feedback, allowing timely decisions and adjustments if the concrete isn’t meeting the early-strength criteria. Waiting until 7 days or 28 days delays this decision and can miss problems that appear early, while testing before placement isn’t possible because there is nothing placed to test. Therefore, the appropriate timeframe is within 24 hours post-placement.