JOB REPORT

Roadworks in progress – traffic keeps moving.

“In-situ” cold recycling on Jingshen Expressway, China

The 658 km long Jingshen Expressway links Beijing to the city of Shenyang in China’s north. Due to the high percentage of heavy goods traffic, a section of the motorway was in need of rehabilitation. The entire operation was to be carried out, however, without closing the section to traffic.

As performance and speed were key factors in this project on account of the high volumes of traffic using the motorway, it was decided to use a combination of “in-situ” and “in-plant” cold recycling.

The operation began with a W 2000 large milling machine from Wirtgen milling off the topmost layer at a depth of 18 cm. A WR 4200 cold recycler from Wirtgen then recycled the underlying layers of the road structure at a depth of 18 cm, mixed the milled material with 3% foamed bitumen and 2% cement, and placed the new base layer – all in one single pass. The cement was injected as a slurry from the WM 1000 slurry mixer.

The WR 4200 cold recycler produced 400 tons per hour of cold recycled mix. One 25-ton 3625 HT single-drum compactor and one HD O 120 V tandem roller from Hamm followed right behind, compacting the freshly paved base layer. While the high-performance recycler from Wirtgen recycled one lane across the full width in one single pass, traffic flowed along smoothly on the Jingshen Expressway.

A 20 cm layer of cold mix was placed in the next step of the recycling operation. The cold mix was produced by a KMA 200 cold recycling mixing plant, which had been set up not far from the construction site. It used the granulated material of the old surface course, adding 2.3% foamed bitumen and 1.5% cement. In the final stage of the construction project, a 4 cm asphalt surface course containing polymer-modified bitumen was placed on top of the cold recycled layer.