The proof rolling requires at least how many passes?

• A. 3
• B. 4
• C. 5
• D. 6

Answer: (C)

Proof rolling relies on applying repeated loads with a heavy roller to test how the subgrade responds. A single pass can’t reliably reveal all weaknesses because moisture pockets, varying density, or fine unstable layers may resist initial compaction. With each additional pass, the soil is pressed more tightly, air voids are squeezed out, and particles rearrange into a denser, more stable structure. After enough passes, weak spots surface through continued deflection or pumping, making them identifiable for treatment. Requiring a minimum number of passes—commonly five—ensures the test is thorough enough to distinguish adequately compacted areas from those needing stabilization. If soft areas still show instability after that sequence, corrective measures are needed before paving.