Which statement best describes a bonded wearing course (BWC)?

• A. A Bonded wearing course is a gap-graded, ultra-thin hot-mix asphalt mixture applied over a thick polymer-modified asphalt emulsion.
• B. A bonded wearing course is a thick, conventional asphalt layer applied directly to the subgrade.
• C. A bonded wearing course uses cold-mix asphalt with standard aggregate.
• D. A bonded wearing course is a surface treatment using asphalt emulsion only.

Answer: (A)

Bonded wearing course is a very thin, durable wearing surface that is bonded to the existing pavement using a bonding layer. It uses a gap-graded hot-mix asphalt overlay placed over a thick polymer-modified asphalt emulsion, which acts as the adhesive. This combination gives good friction and wear resistance with minimal thickness, since the emulsion bonds the new asphalt to the old surface and the gap-graded mix provides the right texture and performance without needing a thick layer. The other descriptions describe different approaches: a thick traditional asphalt layer laid directly on the subgrade, a cold-mix overlay, or a surface treatment that relies on emulsion alone rather than a bonded hot-mix layer.