Precast concrete offers solutions to infrastructure needs

By David Archer

Extending Highway 427 in the Greater Toronto Area was a key priority in addressing the efficient movement of people and goods within the context of the province of Ontario's Growth Plan for the Greater Golden Horseshoe.

The Highway 427 extension provides economic benefits to the province by offering an enhanced freeway route into York Region, the Vaughan Business area and the CPR Vaughan Intermodal Facility. As an essential improvement to the province’s transportation network, the expansion delivers a much easier commute for residents of the area, and reduces traffic on other major routes.

LINK427 is the consortium responsible for the design, construction, finance and maintenance of the Highway 427 Expansion. LINK427 is made up of an international team of designers and constructors, namely ACS Infrastructure Canada, Dragados, The Miller Group and BOT Construction.

The expansion includes:

A 6.6 kilometre extension from Highway 7 to Major Makenzie Drive involving an eight-lane road, a six-lane road, three interchanges, and new median High Occupancy Toll (HOT) lanes.

A 4 kilometre road widening from Finch Avenue to Highway 7 involving four, six and eight lanes and new median High Occupancy Toll (HOT) lanes.

The 427 Expansion had no shortage of obstacles along the way: rivers, creeks, ravines, railways, and other roadways. Consequently, DECAST supplied a wide variety of girder shapes and sizes. As of early 2020, DECAST supplied a total of 223 precast concrete girders of various sizes/designs, from types CPCI1200 to NU2400, with weights ranging from 15 tonnes to 83 tonnes, and spans from 19 metres to 50 metres, supporting precast concrete 90 millimetre deck slabs.

A precast concrete modular bridge system was put in place for part of the 6.6 kilometre expansion. The bridge consists of 22 precast concrete pieces spanning 15 metres and weighing 32 tonnes, and a headwall that weighed 35 tonnes, all placed remarkably in one day. Additionally, DECAST's retaining wall system called GRAVIX® was installed on this project for wingwalls.

The GRAVIX® System (precast concrete retaining wall system) reduces excavation requirements (typically 30% less than conventional Reinforced Soil Slopes (RSS) walls), uses native backfill instead of expensive granular, temporary shoring is not needed, and steel or geosynthetic straps (geogrid) are not required. Eighteen pieces of the GRAVIX® system were supplied and installed in just two days.

In addition to the precast concrete girders, DECAST supplied approximately eight kilometres of reinforced concrete pipe (450 mm to 1500 mm), 291 box culverts (217–1,200mmx2,400mm, and74–2,400mmx 1,500 mm), 200 maintenance hole structures and 150 catch basins.

David Archer, P.Eng. is with DECAST Ltd. 
PHOTOS DECAST and Vivid Air