Factory-built `sandwich' walls: a prefabricated panel can be used for free-standing partitions, highway sound and visual barriers, or privacy walls - What's New

Concrete Producer, The, May, 2003

Over the course of time we have slowly seen precast panels incorporate more technology. In fact the precast concrete panel has become a composite material panel that incorporates concrete and other materials for a set of combined panel characteristics.

A recent patent in this area has aimed at trying to find the best of all worlds by combining materials for thermal and acoustic insulation with materials for structural load characteristics--and making it all adaptable to various applications including refurbishing existing structures. The creative work of inventor Michael Masters of Winter Park, Fla., the plainly titled "Prefabricated Concrete Wall System" is more than the title might suggest. Awarded U.S. Patent No. 6,434,900 on Aug. 20, 2002, the system incorporates structural steel into a foam core and polymer composite sandwich panel.

"Each panel is essentially a factory. built sandwich having an expanded plastic foam core between two composite reinforcing wafers," states the product description. "Each wafer is comprised of an inner layer of fiberglass coated with an exterior layer of concrete reinforced with a grid of steel bats." The fact that these panels are "factory-built" is significant in that it means that the product is probably less expensive than attempting to assemble it in the field.

"The foam core has a pair of vertical cylindrical voids sized and spaced to mate with foundation columns pre-poured onsite," continues the patent document. "The ends of each panel are reinforced with a steel sling lifting assembly embedded in concrete that includes removable eyebolts at the top edge where the panels can be attached to cables at each end for hoisting above the foundation columns and then lowering into place.

"A vertical groove or trough at each end of the panels receives a connector, such as an expansion joint filler. Alternatively the panels can be formed with male tongues at one end and female grooves at the other for tongue-and-groove connection with adjacent panels. The foundation columns can support the panels above ground so that storm runoff waters pass freely under," states the patent application.

A variety of options

It would have been nice to know the combinations of specifications, such as insulating factors and the combined structural loading capabilities, but then that isn't really the nature of patents. Given the number of possible combinations it is likely that virtually any combination of characteristics is possible. However, of some note, and of course adding to the permutations of possible panels, the inventor has designed the system such that it can be produced with several different finishes such as, brick, exposed aggregate, tile, etc. This is not a stamped finish, but the real material.

There was one item in the patent I thought was especially audacious. It is the possibility of incorporating a dovetail joint between the panels in lieu of a simple tongue-and-groove. The panels have an optional interface of either an expansion joint or a dovetail connection. Although I didn't find it specifically mentioned in the patent, I am suspecting that the half-notch on either side of the wall at the dovetail could be filled with grout, sealant, or other filler material for either weather seal or aesthetics. The patent does state clearly that the dovetails must be slid together simultaneously as the panels are slid down over support the columns and footing members.

--PAUL D.Q. CAMPBELL is a Titusville, Fla.-based science and technology writer. You can e-mail him at techpubs@ix.netcom.com or visit http://techpubs.home.netcom.com.