Minimum Horizontal Spacing Between Parallel Main Reinforcing Bars For two parallel main reinforcement bars placed side by side, the minimum clear horizontal distance should be chosen as which of the following?

Introduction / Context:
Adequate spacing between reinforcing bars ensures proper aggregate flow, minimizes honeycombing, and allows compaction around bars. Codes prescribe a minimum clear spacing that depends on bar size and aggregate size.

Given Data / Assumptions:

• Two parallel main bars in the same layer.
• Nominal maximum size of coarse aggregate known from mix design.
• Objective: choose the controlling minimum clear spacing.

Concept / Approach:

The minimum clear spacing should prevent aggregate blocking and allow adequate grout to surround bars. Hence, spacing is tied to bar diameter and aggregate size, and the controlling rule is to adopt the greatest of specified checks.

Step-by-Step Solution:

Verification / Alternative check:

Concrete placement trials consistently show that respecting the largest controlling spacing delivers fewer voids and better consolidation around reinforcement.

Why Other Options Are Wrong:

• Options a, b, c singly may be non-conservative when the other parameter governs.
• Only option d captures the intent to take the largest controlling value.

Common Pitfalls:

Using bar diameter alone and ignoring aggregate size, which can cause blocking and honeycombing in congested regions.

Final Answer:

Greatest value of the above