Pinning Concrete Forms to Asphalt
Learn how to securely pin concrete forms to asphalt for a durable sidewalk.
Last month, I had a job fixing a deteriorating sidewalk. The new sidewalk was to have a 6-in. tall curb beginning at the edge of some asphalt pavement. I needed to install a 2×6 formboard on a slight angle, and I wanted to leave the forms in place for several days after the pour so that the concrete wouldn’t have to do battle with car tires until it had a chance to cure.
Regular steel form stakes would stand above the forms and be a hazard. And there was no way to drive wooden stakes into the pavement. As shown in the drawing, I used 8-in. lengths of 1/2-in. rebar to solve the problem. First, I drilled 1/2-in.-dia. holes in the pavement, 2-1/2 in. deep and on 4-ft. centers.
Next I cut a bunch of Simpson TP37 tie plates in half. I used my modified 3-1/2-in. by 3-in. plates to attach the formboards to the rebar pins. As I ran the four screws that hold each plate to the board, the tie plates bent around the rebar. I then ground off the top edges of the rebar so that they wouldn’t present a problem to a rubber tire.
A week later, when it was time to strip the forms, I noticed a lot of black tire marks along the formboards. Made me glad the concrete had been protected. After unscrewing the tie plates, I used my Vise-Grip pliers to twist and pull the rebar stakes right out of their holes.
— John La Torre Jr.; Tuolumne, CA
From Fine Homebuilding #134
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Depending on what entity owns the asphalt pavement, you might want to consider sealing the holes that you left. In some climates the freeze-thaw cycles will do a number on the edge of the asphalt pavement. Besides, it's simply the right thing to do - you damaged it by drilling the holes, you should make it good.