Delivering Innovation

The A21 scheme involved removing 50mm off the existing asphalt surface, and replacing with a new 50mm thick hot rolled asphalt surface course. In some locations, where National Highways’ designers identified that there might be deep cracks, the planing went down to 130mm to allow repairs to be made before new binder and surface courses were laid.  

The planings taken from the road surface were returned to FM Conway’s Chelsfield recycling depot, where they were processed and sent on to our Erith asphalt plant to be incorporated into recycled pavement material.

FM Conway’s Surfacing team used an app to monitor the rate of spread of the chippings in the new surfacing. The app is linked to an infrared camera, fitted to a smartphone, which can calculate the rate of spread and the percentage of the asphalt mat that is covered by the chippings. Traditionally, this is something a technician would do manually, standing on the newly laid asphalt and taking measurements around working rollers and chippers. The app means the same job can be done much quicker and far more safely from the side of the carriageway. Additional safety benefits come from using a telematics system that creates an accurate record of every load of material that goes down on the road. The system collects data about the material as it is loaded into a truck at the asphalt plant, and then records the time, temperature and GPS location at the time of laying. It can also be linked to temperature sensors in the roller and can incorporate compaction rates.

Challenges and Solutions

Careful planning and collaboration meant the A21 contract was the first work to be undertaken by any of the contractors on the new framework in the Southeast.

“One of the benefits of being the principal contractor is our early involvement, which enabled us to have more control of the programme, so we could plan in the phases from the very start and capture any efficiencies,” says FM Conway framework manager Andy Weymouth.

The business also managed to shave time off the programme, cutting the number of shifts from 25 to just 20. This was partly due to efficiencies, and also because FM Conway advised National Highways that not all the anticipated crack repairs were required.

Outcomes

The scheme was delivered in two phases – the southbound carriageway first and then the northbound. Work started at 8pm each evening, and the carriageway had to be handed back, complete with road markings, by 6am the next morning.

“The collaboration between National Highways, ourselves and the other SDF contractors was key to delivering this scheme,” says Andy. “This was the first scheme under the new framework for everyone, and we had good buy-in from the start from an efficiency point of view and in terms of the quality we were trying to achieve.”