White-topping a sidewalk to correct cross slope?

[ACtrafficengr]

A contractor built a sidewalk with cross slopes of up to 5.7%, instead of 2% max. Rather than make him rip out and replace the affected sections, could bonded white-topping work? It's mostly offset from the road, so curb height isn't a factor in most places.

What items would need attention? I'm assuming some surface preparation would be needed, and control joints need to coincide. If the minimum thickness is over 1/4"(6mm), panels would need to be replaced to transition to existing surfaces to remain. Anything else?

 

[jayrod12]

What kind of climate? I would never allow that to happen here, it would be a rip out and replace. But we're in a cold climate with freeze-thaw cycling and rampant de-icing salt use. Any sort of topping slab thinner than 4" never lasts more than 1 winter.

 

[oldestguy]

Bonding of a grout or concrete, as for overlays in parking garages, can work out fine if some rules are followed.

First APPLY NO WATER!!!!

After roughening the surface,remove the dust by vcuum method. Leave it dry!!! If there is rain, wait until slab is bone dry.

Be on hand with a fresh paste made of Portland cement and water. Just before placing the overlay apply the paste to the surface and spread with a broom. That will enter the pores of old slab and be the bonding agent. Do this immediately ahead of grout or concrete placement. Do the usual moist curing for a week.

 

[ACtrafficengr]

Thanks, Jay. We certainly have wet, cold winters here in upstate NY.

Oldestguy, do you concur?

 

[jayrod12]

I want to clarify my previous statement. In a situation like this, where it seems as though the contractor may not be the most attentive to detail, I would not recommend a thin patchwork topping.

Around here topping slabs may be poured thinner, e.g. parking garage topping slabs, but those are generally performed by competent contractors with significant experience bonding toppings to the base slab. I get a feel that if the contractor blows his slope by almost triple, it's unlikely he'll have the patience and skill to adequately bond a thin topping to and existing sidewalk.

 

[ornerynorsk]

Contractors want an easy out when they screw up. Somebody paid good money for a sidewalk done the correct way. Who pays for replacing the slab when the top coat delaminates, presumably after one winter? Any chance to mudjack the offending sections?

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[cvg]

well first of all, this is just a stinking sidewalk. they could have ripped it out and replaced it by now. It is unlikely that any lasting repair will save a significant amount of money over just remove and replace.
secondly, if you suggest any method to the contractor, they will blame you when it doesn't work. never make suggestions

tell them to replace it. or if they have some idea how to fix it, they need to come up with the method. then make a critical review of the method.

 

[oldestguy]

Mr. Traffic Eng'r: Born and raised in western NY. Here in Wisconsin about the same weather.

One way to check on my method is to cut come cores,and use a chisel to split them at the bond. My bet is it breaks at some other place. My experience is fixing up deteriorated parking garage decks. Should be about the same. Air entrained mix needed both places.

 

[Ron]

OG's recommendations are spot on....I'm from the south and the same applies.

 

[racookpe1978]

Plant a row of trees too close to the low side of the sidewalk. Then, as the tree roots grow, they'll push that side of the sidewalk up. 8<)

That seems to be the way local developers do it down here.

 

[dicksewerrat]

Rip it out and replace. When was this work done? What was the contractors excuse?

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com