In recent years, expanded polystyrene (EPS) has found wide acceptance as a void form. Our investigative research has proved conclusively, an EPS void form requires the same draining considerations as does wood or corrugated paper, or, for that matter, any void cavity, including round voids.

At a 1983 meeting of THE BRIDGE COMMITTEE of THE PRESTRESSED CONCRETE INSTITUTE, it was stated: "Some agencies are not specifying vents and drains in the voids of prestressed beams. Lack of vents and drains could seriously reduce the durability.  We recommend that these provisions be included in all  specifications."

Void Drain Shoe
Specifications for Void Drain Shoe.
(Part # C-VDS)

The Void Drain Shoe, herein after referred to as the shall be constructed of nonferrous, virgin resin devoid of Polyvinyl Chloride, as manufactured by Conasco Plastics, Inc., Columbus, Ohio, or an approved equal.

The design, composition, and installation of the Shoe shall allow for the free flow of concrete in and around its bearing surface and be of sufficient strength to withstand the stresses placed upon it associated with the manufacturing process.

The Shoe will be of a color which shall contrast with the concrete to assure proper application and positioning prior to placing the void form. Arrows, referencing alignment of the void drain/vent/chair and the Shoe to the length of the void form, shall be molded into the top surface of the Shoe.

The bearing surface of each Shoe shall have an minimum bearing area of 16 square inches (4” X 4”) to provide for a stable platform in the area of each void form it supports. A center relief shall allow access to the top of the void drain/vent/chair device and the “knock out,”molded therein, providing a bearing lip to contain and properly position the drain tube, allowing for accurate placing of the void form to a height tolerance of -0 and plus 1/8” prox. (When Shoe is used with the F-Series void drain/vent/chair, an adhesive to join and fasten Shoe to the drain/vent/chair is suggested.)

Projecting “spikes” molded along the longitudinal dimension of the bearing surface, are an integral part of the Shoe made to provide a mechanical engagement and assist in holding the alignment of the corrugated paper, and expanded polystyrene (EPS) void forms, and to provide a “cradle” into which round, solid fiber void forms may be fixed and rested. Slots, located immediately inboard of the spikes are provided to accommodate the use of nonferrous strapping, supplied by others, to mechanically tie the Shoe assembly to the void to further secure and align void forms, as may be required.

One void drain Shoe shall be installed with each void drain/vent/chair device.

Void Spacer Alignment and Hold Down System
(Patent application in progress)
The Void Spacer Unit. Part number C-VSU.

As is most often the case, if you listen to the customer, he will tell you what is needed. This is the case with the development of the Conasco SHOE (Part number C-VDS), used extensively in conjunction with the Conasco void drain/vent/chair, to support, align and position void forms in box girder deck slabs. It doesn’t take very long for one of our customers to come up with another use for a new product. Enter the spacer concept.

The first use was by a large east coast girder producer who latched on to a big railroad girder job, requiring piggy back EPS void forms. He used the sample enclosed, to space the void forms vertically.

At almost the same time, another customer came up with the exact same concept but his application was to space EPS voids from the form horizontally.

We mulled it around a bit and decided there was a use for this spacer concept for both round solid fiber void forms as well as rectangular EPS void forms. In our concept drawings, of our hold down system, I have marked with a red X where I envision this device to be useful.

While we use a bright yellow for a visual reference for a top screed line for the first stage pour of a rectangular voided girder, if the concept proves merit, we could easily make a concrete color SHOE for
horizontal spacers that bear against the side forms.