Welland good

All’s well and good at the Welland Canal in Canada – particularly in relation to the new POLYFLEX-ADVANCED flexible plug expansion joints of its Lock 2 Road Bridge

The Welland Canal connects two of North America’s great lakes, Lake Ontario and Lake Erie, providing an alternative route to the nearby Niagara River which the mighty Niagara Falls, with their 51-meter (167-ft) drop, make unnavigable for shipping. The canal – a key element of the St. Lawrence Seaway which makes the Great Lakes navigable from the Atlantic Ocean – has eight locks, which enable the total level difference of approximately 100 m (328 ft) between the two lakes to be negotiated safely. A bridge at Lock 2 carries Niagara Regional Road 83 across the canal, with one section of the bridge rising when required to allow ships to pass as they transport roughly 40 million tonnes of cargo along the canal each year.

In early 2017, as part of an overall bridge renovation project, new POLYFLEX® ADVANCED expansion joints, for SLS movements of 30 mm (1.2 inches), were installed at four structure axes, replacing bituminous plug joints that had proven unsatisfactory in the past. Such bituminous/asphaltic plug joints have long been plagued with durability problems, especially at low or high temperatures. Inconsistent quality due to improper mixing and incorrect temperature during installation (high temperatures required) also frequently cause problems.

POLYFLEX®ADVANCED flexible plug expansion joints, with a flexible driving surface of high-performance polyurethane, might be thought of as the modern version of bituminous plug joints. Like the traditional plug joint type, they create a smooth, safe, low-noise surface, and offer great adaptability and easy installation, but they additionally offer greatly improved reliability, strength, elasticity and durability. They also offer greater movement capacity, uniform material behavior at very high and very low temperatures, and easier installation at ambient temperatures. And the speed of installation and curing of the material is particularly beneficial when the joint is installed on an existing structure to replace an old expansion joint – as was the case in this particular project.

With this far superior type of expansion joint now installed in the structure’s deck, the bridge’s owner can be confident that the joints will perform well for many years to come.

The bridge crosses the Welland Canal just upstream of the canal’s Lock 2

Cross section of the new carriageway joint, showing an optional polymer concrete base that may be used as required – e.g. to form a suitable subsurface for the poured POLYFLEX® material or to reduce the depth of POLYFLEX® material required (and also forming an ideal connection to the bridge deck’s waterproofing membrane at each side)

Preparation of recess following removal of the old expansion joint

Cutting of slots adjacent to joint for asphalt-strengthening support ribs of polymer concrete

Filling of cut slots with polymer concrete to form the asphalt-strengthening ribs – and placing of a polymer concrete subbase within the recess as required

Cutting to size on site of perforated steel angles at both sides of the movement gap, and a cover plate across the gap to prevent loss of the fresh poured material and for the purpose of stress distribution

Application of primer by brush, and of duct tape to protect adjacent surfaces, following drilling of holes in substructure and insertion of fixing anchors

Pouring of first layer of POLYFLEX material

Pouring of first layer of POLYFLEX® material

Anchoring of pre-cut perforated steel angles in place

Pouring and levelling of remaining POLYFLEX® material flush with the connecting road / footway surfaces

This type of joint can be installed to perfectly suit the most challenging surface geometries

One of the bridge’s POLYFLEX® ADVANCED expansion joints, showing the ROBODUR® asphalt-strengthening ribs at both sides

A fully installed expansion joint during an inspection by a mageba POLYFLEX® ADVANCED specialist