What cylinder sampling method is used for FDOT strength testing?

• A. Collect a representative composite sample from the discharge, fill cylinders in layers per spec, cap and label, then cure.
• B. Take a representative sample from the top layer only.
• C. Use pre-cast cylinders from supplier.
• D. Use the last portion of discharge.

Answer: (A)

The method used for FDOT strength testing relies on getting a representative composite sample from the discharge and then preparing the cylinders in layers per the specification, followed by proper curing and labeling. A composite sample captures the variability in the batch, ensuring the cylinders reflect the actual concrete being placed rather than just a portion of it. Filling in layers helps prevent segregation and trapped air, which can skew strength results. Proper curing preserves the hydration process so the measured strength reflects the intended mix design. Sampling only from the top layer or from the last portion of discharge can produce biased results, while using pre-cast supplier cylinders may not represent the field mix and curing conditions.