The N12 (Section 19 and 20) serves as a strategic link between Johannesburg and the N4 Maputo Corridor to Mpumalanga. It is located in the main coal mining region of the Mpumalanga Province. This emphasises the strategic importance of the road.
The condition of the road was determined via a detailed investigation and instrumental survey, including rutting measurements, deflection and roughness, as well as the riding quality, all of which indicated a road in distress.
The remedial measures entailed the milling, construction of base layer with a sub-base layer in selected areas. Surfacing consisted of:
- Slurry texture treatment in the fast lane, slow shoulders and the ramps.
- Replacing the asphalt with an A-E2 modified asphalt and a 16.0 mm bitumen rubber single seal in the slow lane. This prevents rutting and ensures that the skid resistance in the slow lane is maintained longer.
- Construction of a 13.2 mm bitumen rubber single seal in the fast lane, shoulders and ramps.
- Repair of an 11 km section of concrete pavement by means of extensive concrete patching, repairing and sealing of joints.
- Construction of a slurry treatment and 16.0 mm SAMI over the concrete pavement.
- Construction of a new Bitumen rubber Asphalt overlay over pre-treated concrete pavement to improve the riding quality and placing a mix capable of accommodating slight movement over joints.