PEC can be nailed to wooden forms or pushed or vibrated into poured concrete. A 3" clearance is recommended from concrete edges or corners.
3.1 Installation in concrete forms
PEC shall be installed inside the concrete forms in accordance with the shop drawings prior to pouring concrete. Place PEC in the designated locations with the surface of PEC in contact with the form. PEC shall be secured to the wooden forms by means of nails driven from the inside of PEC into the forms (see Step 1 drawing). All exposed nails shall be clipped at the surface of PEC after removal of the forms (see Step 2 drawing).
3.2 Fabrication
PEC can be prefabricated into frames and vibrated into freshly poured concrete. Small air vent holes shall be drilled in approximately 3 feet intervals in the surface of PEC prior to its placement into fresh concrete.
Butt welded connections are made by extrusion welding the back side of the 3.5" surface and the outside of the legs. Backup HDPE plates are sometimes used behind the surface to be butt welded to reinforce the connection. A very flat extrusion weld bead is then placed on the 3.5" surface. PEC can also be butt welded similar to HDPE pipe welding techniques (See Figure 1). The two pieces (A & B) to be welded are laid on a flat surface. Each piece is held in contact with the "welding mirror" (C) for approximately 45 seconds until a melt bead (D) forms at the mirror; the mirror is removed (E) and the pieces are pushed together (F) fusing the molten plastic. The process gives a full perimeter weld of the PEC. Care must be exercised to assure alignment of the channels after the weld. This method can also be used for miter joints.
It is necessary to prevent gaps or repair gaps caused by thermal contraction or improper placement of the PEC. The liner-to-PEC connection will not be water tight unless the PECs are properly joined at their ends. Other PEC installation details are available from Poly-Flex, Inc.
3.3 Seaming
All seaming shall be done in accordance with the Poly-Flex extrusion seaming procedures, as outlined in this manual, and by experienced technicians who are qualified by Poly-Flex, Inc. to seam Poly-Flex liners.
The following steps shall be followed prior to welding Poly-Flex liners to the PEC:
Remove cement paste, form oils, curing compound or other contaminants from the surface of PEC. The 3.5" wide surface shall be clean and dry. The welding surfaces of the PEC can be taped prior to its installation. The tapes are removed after the concrete is hardened to expose the clean surfaces of PEC for welding.
Use a hot air gun to tack liner to PEC in a straight line in the center of the PEC surface.
A grinder with 80-grit disc shall be used to remove the surface contamination and oxidation from the welding surface area prior to the extrusion welding. Place the extrudate on the center line (see Step 3 drawing). All air vent or nail holes shall also be ground and covered with the extrudate.
All seams shall be nondestructively tested, whenever possible, by
using a vacuum box apparatus if the PEC connection is designed to be waterproof.
Since no destructive seam testing is possible, it is very important that the seaming be done by Poly-Flex qualified technicians and/or qualified representatives of Poly-Flex dealers.
