Question: We manufacture precast concrete site furnishings with fiberglass molds. We currently use a sticky-back foam on the flanges. But we are still having leakage at the seam. The forms are keyed and bolted together at a 3-inch spacing. Is there a material we can use in place of the sticky tape that will not stain the concrete?
Answer: It sounds like the problem is more related to the mold bolts is the most common cause of shell warping. One tip for avoiding shell warping is to loosely install all mold bolts before making them snug. One producer suggests adopting a mold-bolt tightening pattern, similar to tightening a tire's lug bolts, alternating from side to side. When mold shells are in good condition, many producers use paraffin or a petroleum-based jelly lubricant Worn or shrunk rubber liners also can cause leaky seams.