CONSTRUCT2012 Education Session W01 - Avoiding problems with floor finishes on conc slabs

CSI CONSTRUCT2012
Avoiding problems with floor finishes on conc slabs
Emily R. Hopper, Peter Nelson of Simpson, Gumpertz & Heger, structural engineers and building science
Wed 9/12/2012 8:00

Adhesive failures
- moisture, or ph. Adhesive oozes.
- or edges of vct curls.

Wood flooring
- dimensional change problems
- biological degradation - mold/mildew

Carpet
- debonding
- phthalates released

Resinous terrazzo
- debonding
- curling
- blistering

Silicates
- surface of floor becomes hygroscopic, wet, slippery

Concrete e.g. Exposed agg or ground face
- alkali silica reaction

Why?
- Change in government regulations and sustainable design requirements. We no longer use asphalt cutback adhesive. Need to meet VOC limits. So we're using water-based adhesives, that fail when they are re-wetted.
- Increased use of pozzilans e.g. fly ash
- Lightweight conc saves a lot in steel framing and increases fire ratings. But lightweight aggregate takes twice as long to dry. E.g. 160 days instead of 80 (may vary depending on thickness of conc).
- if any significant rain is allowed to fall on the conc, you have to start the 80 or 160 days all over.
- Fast track construction
- Lack of or compromised vapor retarder below slab

Suggested solutions:
- Require low w/c ratio
- Consider requiring plastic moisture retaining curing covers , and not allowing curing compounds, burlap, and definitely not continuous water fog curing.
- Avoid blotter layer. It usually becomes a bathtub, in spite of the best intentions.
- {Make CA staff aware to} expect to see many not just one calcium chloride tests. See the spacing requirements in the ASTM. Three tests for first 1,000 sq ft. One more for each additional 1,000 sq ft.
- {Make CA staff aware to} expect to see where they ground away any curing compound or other surface treatment if any.
- regarding use of ASTM F 2170 Internal RH probe test, instead of ASTM F 1869 anhydrous calcium chloride test - most people do not have equipment that passes the standard's requirements for statistical error. A study was done of several mfr's probes, results were all over the place, and retested later and results weren't even consistent among a mfr's own probe.
- If this method is used, {make CA aware that} the tester needs to brush, vacuum, and repeat until there is no dust. And the report should show a number of things listed in the ASTM, including the make and model of tester and when it was last calibrated.

pH is a big issue too. But nothing can be done about it. Also since it requires moisture for it to be a problem, we expect ASTM will eventually say fix the moisture problems and you will fix the pH.

Who should do the moisture testing?

Who should hire the tester?

Recommend independent, hired by owner.

Intl conc repair institute (ICRI) now has a certification for testers.

Vented metal deck - don't use as a moisture mitigation strategy. Won't hurt but doesn't help much.

"Accelerate" drying of the slab - not much data

Install moisture mitigation system
- assume you are going to need it up front. So many factors, and not one person's responsibility
- consider an allowance, alternate, or unit price - {though after discussion, agreed somewhat with a plan to just include whatever methods the GC chooses to manage it in the base bid, with mitigation as one option}
- systems are not all created equally. See slide for types of moisture mitigation. Speaker believes best type are 100% solids epoxy based topical products that are pH tolerant, with 0.1 perms or less. {need to discuss further, may be too restrictive - perhaps 0.3, and retesting is the key.}
- include the shot blasting, and a special type of blotter layer for the coating(?),
- expect $5-10/sq ft, in the base bid.

Avoid:
- penetrating coatings,
- water-based types, will have the same problem we started with because they will break down from moisture.
- magic admixtures that will lock water in and can't be tested, cause pH and bonding problems and doesn't address cracks.