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When placed in the sidewalk at regular jointing intervals, the diamond-shaped TripStop forms a double-keyed joint, allowing the sidewalk to articulate around the product. The joints can be cut onsite using a fine handsaw or with a combination saw with a fine-tooth blade. The product is secured with steel pegs driven through pre-drilled holes prior to the concrete pour. Photo: Jonathan Gano

That method does, however, still require tooling the joint into the surface of the newly poured concrete directly on top of the buried PVC rod.

In both cases — the TripStop installation or the in-house square PVC installation — the repaired sidewalk sections simply butt against the unrepaired existing sidewalk. That creates a cold joint between the new slab and old slab, setting the stage for future faulting.

IN-HOUSE INNOVATION

The tree roots usually continue to grow and destroy the aggregate interlock at the cold joint, lifting the entire repaired section.

Springfield's sidewalk crews found a way to transfer the load from one panel to the next across the cold joint using PVC by suspending a half-round rod between the forms before the concrete is poured. By drilling pilot holes and attaching the PVC rod with concrete anchors, it forms the same keyway at the cold joint and is mechanically anchored to the original, unrepaired section.

With the half-round PVC rod, the sidewalk has a much greater ability to accommodate movement and resist faulting.

Although the in-house jointing method adds to the installation cost of the sidewalk, it also offers cost savings resulting from eliminating the need for unnecessary future repairs.

A typical sidewalk repair lasts nearly an hour, and prices of PVC vary, particularly for the generic PVC round and square rods produced locally or regionally. Still, managers should expect to spend $3.50 to $7/joint. On a typical joint spacing of 5 feet, that amounts to an additional 75 cents to $1.50 per linear foot for the cost of the sidewalk.

“Considering that joints installed with TripStop are expected to last up to 10 times longer than those installed traditionally, the impact on Springfield's maintenance budget will be big,” Hall says. “It'll take a few years to actually see the payoff, but so far every installation is working.”

— Jonathan Gano is the superintendent of streets for the city of Springfield, Mo.