corroding nosing bars

[samdamon]

An existing cast in place framed concrete stair I am reviewing has numerous locations where the treads have cracked due to corrosion of nosing bars. Am having probes and tests done but my guess at this point is that lack of cover plus frequent salting have resulted in the nosing bars corroding and then spalling the concrete.

The question is how best to deal with the rebar corrosion long term. The nosing bar corrosion is not really reducing the structural capacity of the stairs, but the client does not want to see rust stains and cracking/spalling anymore. I don't see removing the loose concrete, cleaning the rusting bars and then patching as a complete fix. Additonal cover cannot be added as part of repairs because it will distort the dimensions of the treads. This also appears far too small a job to use csthodic protection.

I am considering just cutting the nosing bars out completely. There is an existing bottom mat of bars (which are in ok condition) each way in the bottom of the 8" thick stair slab, which can be counted on to tie everything together. The stair is about 18' wide.

Has anyone tried removing nosing bars and patching?

 

[dik]

You can use an epoxy patching material (Sikapatch or something of that ilk). I haven't used nosing bars for 30 years... used to be common, but I've encountered lots of problems using them.

 

[hokie66]

I agree. Cut them out and do a concrete repair. I don't know why we used to specify them, but it was a bad idea.

 

[racookpe1978]

The nosing trim is there because the concrete "edges" (the actual sharp corner of the tread) will easily crack under the repeated steps. A more rounded corner - like on a curb - resists this cracking, but stair steps have to be sharp-edged for traction.

Pull out the rusting trim, replace it with a fiberglass or plastic trim piece - I've used the safety-reflective edge piece inserts outside on stairs for this when I've made repairs in the past - and set the new trim pieces in the two-part epoxy resins mentioned above. The new trims will seldom exactly fit back in the slots left from the old rusted parts.

 

[apsix]

racookpe1978
The problem here is corroded reinforcement bar, not trim.

 

[jike]

dik and I have the same exact philosophy...don't use nosing bars!

Cut them totally out and then patch the concrete.

The epoxy patch will be a much darker color than the original concrete. A cementatious patch will be closer but most likely will be a different gray color but not as far off. You may want to consider applying Thoroseal to the stairs for a uniform color after the repairs are made.

 

[dik]

In addition to causing corrosion problems, they act as a hard point and promote fatigue tensile cracking of the step nosing. To reiterate, don't use them!

 

[Teguci]

Might want to consider installing a Wooster nosing product.

 

[dik]

use wooster nosings nearly all the time... great for traction.

Dik