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Bubbling and apparent delamination of a new floor tile system installed on a concrete slab that is below the building exterior soil grade. Why is this occurring?

Background: The space was a section of the first floor of a twin tower, multi story health care facility. The first floor is common to both towers and is on a concrete slab that is below the building exterior soil grade.

The focus of this investigation is a section of the first floor, which had new strip floor tile installed approximately one year prior. This tile has three layers, a rubber base layer, and middle color layer, and a top wear layer. Prior to instillation, the old floor system was pulled-up and the associated adhesive was removed from the concrete slab using a chemical mastic remover.

The Condition: This investigation was implemented in response to areas, after the new tile was installed, of milky white 1-3 inch diameter spots appearing in the tile as the wear layer began delaminating from the color layer. Eventually the tile itself began delaminating from the concrete floor.

The cause of the tile delamination was suspected to be a result of excessive water vapor emission rates from the concrete slab and/or excessive emission rates of volatile organic compounds from the concrete slab that are incompatible with the new tile or adhesives. Residual contamination of the concrete from the chemical mastic removers used to remove the old tile system is suspected.

Two locations were selected for measurement of water vapor and volatile organic compounds emission rates from the concrete sub-floor. One location was where the floor tile was delaminating heavily and was an area where the chemical mastic remover was used and the other location was where no floor tile delamination was occurring and where the chemical mastic remover may not have been used.

The Diagnosis: We measured the water vapor emission rates from the concrete sub-floor at three locations utilizing anhydrous calcium chloride domes. Water vapor emission rates through concrete slabs are effected by factors such as the moisture content of the soil underlying the slab, the condition of the capillary break and the vapor-retarder beneath the slab, the porosity of the slab, the material composition of the slab, as well as environmental conditions of the building environment above the slab. This test may be used for determining the acceptability of installing specific types of floor coverings on concrete slabs.

• The water vapor emission rates from the concrete floor at the area of delaminating tile in the was 4.0 lbs/1000 ft2 - 24hrs, which is less than the rate of 5.4 lbs/1000 ft2 - 24hrs which was observed from the concrete at the area of non-delaminating tile. This suggests that the primary source of the tile delamination is not excessive water vapor emissions from the concrete slab. This conclusion is also consistent with our observation of delaminating tile occurring in those areas where chemical mastic removers were used.

We measured the airborne concentrations of volatile organic compounds using a solid phase multi-sorbent sampler and a gas chromatograph with a mass spectrometer detector and an emission cell to measure the emission rates of volatile organic compounds from the concrete sub-floor. This test is used to determine if residual contamination of the concrete from the chemical mastic removers used to remove the old tile system is present.

• The emission rates of five volatile organic compounds were substantially higher at the location with the delaminating tiles than at the location without the delaminating tiles. These compounds included butoxyethanol (ethylene glycol monobutyl ether), ethylbenzene, methyl-2-pentanone (MIBK), propanone (acetone), toluene, and xylenes. These elevated emission rates of volatile organic compounds from the concrete are consistent with those compounds listed in the MSDS for the chemical mastic remover.