Is under tolerance of mixing depth allowed?

• A. Yes
• B. Sometimes
• C. Only with approval
• D. No

Answer: (D)

Mixing depth is set with a tolerance to ensure the treated layer is uniform and strong enough across the project. If the actual depth is shallower than specified, you haven’t fully mixed the material to the designed depth, which can leave weak spots, poor bonding with adjacent layers, and reduced stability and drainage performance. Because the integrity of the stabilized or treated layer depends on reaching the full depth, under-tolerance is not allowed. Any shortfall typically requires rework to achieve the required depth, and approvals do not usually waive this requirement.