Acrylic Adhesive for Threaded Rod Installed in Solid Concrete

Anne, I use the "Substrate Specific Adhesive - porous materials (except for wood)" category for all concrete anchor adhesives. The VOC limit is 50 g/L. Hope that helps.

Hi Lyle—I think you’re right. SCAQMD defines porous material as “a substance which has tiny openings, often microscopic, in which fluids may be absorbed or discharged,” and offers examples that “include, but are not limited to, wood, fabric, paper, corrugated paperboard, and plastic foam.” Based on these examples, I have a heck of a time classifying concrete as “porous” and the definition does not delineate an absolute threshold between "porous" and "non-porous."

However, a 2007 LEED Interpretation addressed whether to classify concrete as a porous or non-porous substrate. LI#1822 held that, if a substrate could qualify as either porous or non-porous, it is correct to apply the most restrictive criteria. Since 50g/l is more restrictive than most other alternatives on the list, it is probably the right choice.

Incidentally, I have had very little luck finding VOC data for “Red Head A7 Acrylic Adhesive.” I am not sure whether it meets the 50g/L limit.

Hi Jon. As a Building Envelope guy, I can definitely confirm that concrete is a porous material - it's capillarity and hygric storage potential can be either a benefit or a hindrance, depending on it's relationship to the building envelope control layers.
I don't know the VOC limit for Red Head A7, but I know that Hilti HY-150 Max has a VOC content of 7 g/L. Given that HY-150 is epoxy and Red Head A7 is acrylic, this could an apples and oranges thing. There are some conditions that would cause the structural engineer to specify acrylic vs. epoxy, but oftentimes either will do given that it meets strength requirements and code approvals.

Concrete can definitely take on water, but it is not nearly as spongy as the materials that the definition gives as examples. Everything is relative. As a metrics guy who also works in code enforcement, I prefer clear cut definitions. The SCAQMD definition of “porous” is awfully mushy. It would be clearer if it used a measurable, non-subjective threshold of, say, capillary or hygric storage potential.

I have found something on a third-party website saying that ITW Red Head A7 Acrylic Adhesive contains 2g/L VOC, but I could find no actual VOC data from the manufacturer. The same website called this product as a “Multipurpose Construction Adhesive” with a 70g/L limit, but I have found little to support that classification.