An engineer at a local water department recently asked us if we could epoxy-inject leaking cold joints in one of their water tanks. We've never injected cold joints, and we couldn't determine the exact places along the cold joint that were leaking. Can leaking cold joints be injected? Where do we set the ports?
ccording to John Trout and Gary Hayes of Lily Corp., cold joints, unlike cracks, are not voids in the concrete they are merely seams, containing no appreciable voids. Therefore, as a general rule, they cannot be injected. However, many cold joints do have small voids in areas where the concrete is not completely consolidated. Also, if water is passing through the cold joint, you can safely conclude that the concrete is at least porous enough to be saturated with low-viscosity epoxy resin injected under pressure. To find the sources of the leaks, use compressed air to blow the concrete surface dry around the cold joint. Then watch to see what areas wet out first you'll want to place your injection ports there. Drill 1_2-inch-diameter, 1-inch-deep holes using a wet diamond bit. Don't use a dry bit because it will impact the wet dust into the void and block the penetration of epoxy. Also, you don't have to apply a seal to the whole cold joint; sealing an inch or so on each side of the port should suffice. After you've placed the ports, drain the tanks below the level of the cold joint and wait a few days for the concrete to lose some of its moisture. Then, using a low-viscosity epoxy (200 cps or less), inject the cracks at as high a pressure as possible for as long as the pot life of the epoxy permits. If epoxy emerges from the inside face of the concrete, you'll see a noticeable drop in pressure.