Why do we use concrete shoulders with PCC lanes when asphalt concrete shoulders are less expensive?
Tied concrete shoulders (with tie bars) provide stress reduction along the longitudinal joint between the outside lane and the shoulder. The largest amount of stress from truck tires is along the outside edge of pavement, so the tied shoulder spreads the load more uniformly across the longitudinal joint. An asphalt concrete shoulder does not connect to the PCC and does not provide that edge support like a tied PCC shoulder. Normally, over time, there will be shoving of the asphalt between the lane and shoulder. Remember, the outside lane is normally where trucks are traveling. Truck axle loading is the main distress that pavements endure. The HDM does allow an alternative design of asphalt shoulders with a widened PCC slab. This option keeps a 3.6 m (12-ft) lane width, but the concrete is paved at 4.27 m (14-ft) wide with an AC shoulder. The widened slab provides an approximate 0.6 m (2 ft.) buffer between the edge of travelled way and edge of PCC which reduces the edge stresses on the
