What is proof rolling and its purpose in subgrade work?

What is proof rolling and its purpose in subgrade work?

• A. Heavy rollers test for soft spots to ensure uniform compaction and identify unstable areas.
• B. Rolling to make the surface shiny.
• C. Testing with water to measure porosity.
• D. Painting lines on pavement.

Answer: (A)

Proof rolling uses a heavily loaded roller to test the prepared subgrade or subbase for stiffness and bearing capacity. The goal is to locate soft spots or unstable areas that haven’t reached adequate compaction under load. As the roller passes slowly, you look for noticeable deflection, rutting, or pumping—signs that the soil isn’t yet able to support the pavement structure. When these spots are found, you rework them with additional compaction or stabilization so the entire surface has uniform strength before placing base and pavement. This helps prevent future settlement and pavement distress. It’s not about making the surface shiny, measuring porosity with water, or marking lines.

Proof rolling uses a heavily loaded roller to test the prepared subgrade or subbase for stiffness and bearing capacity. The goal is to locate soft spots or unstable areas that haven’t reached adequate compaction under load. As the roller passes slowly, you look for noticeable deflection, rutting, or pumping—signs that the soil isn’t yet able to support the pavement structure. When these spots are found, you rework them with additional compaction or stabilization so the entire surface has uniform strength before placing base and pavement. This helps prevent future settlement and pavement distress. It’s not about making the surface shiny, measuring porosity with water, or marking lines.