For a panel with largest aggregate size 3 inches, the minimum clear distance between parallel bars should be at least how many inches?

• A. 3 inches
• B. 4 inches
• C. 1 inch
• D. 3.5 inches

Answer: (B)

The spacing between parallel bars must be wide enough to accommodate the largest coarse aggregate used in the concrete, so the aggregate can pass through and not bridge between bars as the concrete is placed and compacted. When the largest aggregate size is 3 inches, you need enough clearance to allow that material to flow around the bars and for proper finishing. Adding a practical margin of about 1 inch yields a minimum clear distance of four inches. This extra clearance helps prevent voids and ensures good compaction and bond around the bars. Smaller spacings, like three inches or less, would not reliably allow a 3-inch aggregate to pass, making four inches the appropriate minimum.