Question: I am searching for a supplier of inflatable formwork for constructing culverts onsite. I believe the balloon-like apparatus comes in different sizes, but I can't find a source.
Answer: Two articles appeared in Concrete Construction magazine in 1987 and 1988 describing the use of such a product, but no source was provided. You can view these articles at www.concreteconstruction.net. Select “News and Past Articles” and search for “inflatable, culvert.”
There's also a 1994 research report from the Iowa DOT covering the use of a product called Air-O-Form in a demonstration culvert program in Washington County. For a link to this information, go to www.concreteconstruction.net.
U.S. Patent #4723751 was issued in 1988 for an “Inflatable form for concrete structures”—which is viewable on the Web using Google's patent search—but unfortunately we have not been able to find a current source for this product. We'd be glad to hear from readers who know of a source.
A similar technology is offered by Monolithic. The company uses its Airform to provide a base for shotcrete construction of domes and other structures, but these typically are round rather than long. More information is available at www.monolithic.com.
The closest thing we could find for forming culverts is a collapsible system for box culverts made by Wadco. Check out www.wadco.com—look for “collapsible.”