Form Oil Used to "Cure" Slab on Grade 3

[OrangeVest]

Nox-crete form oil was mistakenly applied to 15,000SF of slab-on-grade instead of the spec'd water-soluble dissipating curing compound. Three days later, a concentrated degreaser was used to remove it and apply the correct compound. Aside from the material compatibility issues with flooring that should be solved with the degreaser, from a curing standpoint is this slab doomed or did the form oil at least provide some measure of protection during the first 48 hours? Will applying the correct compound at this stage help? Any suggestions to avoid grinding/removal appreciated.

 

[StephenA]

Try taking cores and test those. At least there is no argument then.

 

[GeoPaveTraffic]

The form oil may have helped to hold moisture in the slab, but I would not count on it. I would say that the future of the slab is dependent on the weather conditions during that 48 hours and the long term exposure conditions that the slab will see. If the weather was relatively damp and cool then the curing compound would not have added a lot to the slab, however, if it was windy, low humidity, sunny, etc. then the surface of the slab definatly suffered.

I completely disagree with StephenA, taking cores would not answer any questions. You might be able to have a petragraphic analysis done of the surface of the cores, but I'm not sure what they would even look for.

 

[OrangeVest]

Weather during the 48 hours was fair (low 40-deg, high 62-deg) with no precipitation. Humidity levels ranged between 70% at night to 30% mid-afternoons. This is an interior slab.

 

[SlideRuleEra]

As is so often the case, "the devil is in the details". I see twelve different types of Nox-Crete Form Release Agents

http://www.nox-crete.com/prod_form_release.html

Which one was used?

Data sheet for the general-purpose product, Chembeton, has disturbing statements like:
"...react with excess limes in fresh concrete..."
and
"Not generally recommended for use on architectural concrete"

Assuming that you are the Engineer, a good way to handle this type situation is to require the Contractor (or whoever was responsible for using the wrong product) to provide the Engineer (and Owner) with proof why the concrete is acceptable.

http://www.SlideRuleEra.net

 

[OrangeVest]

The product used was "Nox-Crete Form Coating," which is one of the 12 products listed on the website from the previous posting.

 

[SlideRuleEra]

Well, at least this product does not have as many menacing statements. As GeoPaveTraffic, says it probably provided some level of protection. Despite the degreasing, the carpet issue may come back to "haunt" everyone (see the Data Sheet precautions about foam rubber).

IMHO, because of the uncertainly, "somebody" is accountable to the Owner. By that I mean, either a "technical" solution - remove the concrete and place it again.
or
A negotiated "financial" settlement to compensate the Owner for a finished product that "MAY" or "MAY NOT" meet the intent of the specification.

As an Owner's representative, I would insist on a letter from Nox-Crete, stating their opinion on this specific situation. At that point a decision could be made about a potential financial settlement.

On your question about applying the proper coating now - not worth the trouble.

http://www.SlideRuleEra.net

 

[GeoPaveTraffic]

At this point I agree with SlideRuleEra.

 

[Rjeffery]

Another possable solution is to grind the upper (1/4 inch?) that was "contaminated" with the form oil at the contractor's expense.

 

[Ron]

The form oil is a relatively light oil and probably provided some protection against water loss. The use of a solvent degreaser probably took more moisture out of the slab than you wanted. At this point, there isn't much point in doing anything, except re-wetting the slab.

If you spray water on it and it beads up, you haven't removed all of the oil or it continues to bleed from its penetration depth.

At this point I would probably recommend sealing the slab with a high solvent methacrylate penetrating sealer, thinned with a high flash solvent to penetrate quickly and evaporate fully.

 

[jeff805]

Using UltraHigh Water Jetting with Vacuum may solve the problem. The 30,000 to 50,000 psi water will take a small amount of the concrete top off and (depending on the tool used) may expose some of the aggregate, but it will get in and clean the porous areas that may still have oily contaminant remnant. Using a high air flow vacuum will take care of the rest.

 

[crossframe]

You may exercise caution with this last method. I've seen this used in the past to remove portions of bridge deck to expose the steel girder below.