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Question DetailsAsked on 10/17/2017

can hydaulic cement be used to fill large voids?

the void is at the entrance to a pond spillway culvert. The metal tubes have 1' x 2' hole rusted in the bottom, with dirt about 3-4" below. should I use hydraulic cement to fill these vids or use regular cement or sand mix first, then hydraulic cement or something else t seal the patch?

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I would not call a few cubic foot hole (assuming the hole around the culvert is not highly eroded out. If you are only talking a couple of cubic feet of hole you would just use hydraulic cement for it all - not a major added cost, but not really needed for this application.

I would dig out loose material and pebbles and such in the hole (assuming you can reach in there), and then dry-pack it with regular Portland cement and sand mix (or sackcrete if a large eroded out hole) - to maybe a couple of inches just around and behind the hole. This I would use a power grinder or such with wire brush/grinder wheel to roughen and derust the hole area, coat with a rust converter like naval Jelly to stop the rusting, clean that when dry to remove the gel residue then use an epoxy-modified patching cement to fill that last couple of inches AND also to overcoat the rusted out area in the culvert with an inch or so of the patching cement. If you cannot keep the area dry during patching, then the hole in the metal could be patched using an underwater pool repair epoxy or hydraulic cement (assuming the water flow is minimal so wouldnot erode the material before cured).

Another way to attack it which may actually last longer is to bring the hole filling cement mix/concrete right up to the bottom of the hole in the culvert, then use fiberglass mesh and automotive body filler to patch the actual hole in the culvert plus about 1/2" thickness over it. Course, has to be dry to do that.

Most permanent repair forthe steel, if you can come by right size scrap, is take a scrap of culvert and weld if over the hole, using about 3-4 inch overlap beyond the rusted out edges. prep the rusted metal with Rustoleum rusty metal weldable primer first to keep the rust from immediatley attacking the new metal. Of course, line up the corrugations so the patch will not stick out into the flow - with a touch of hand sledge work you should be able to hammer the repair into place pretty tight - weld one end in place first, then work along toward other end hammering into place and tack welding as you go, then once it is all tacked in tightly full fillet weld all around the edges. [Reason for the hammering is a piece of same-sized culvert will be slightly oversize diameter to act as an interior patch, so you have to hammer it out to bend it down into a fairly tight fit with with the existing culvert.

Of course, if the hole is right at the inlet you may be able (depending on water level issues) to dig out the inlet and just apply a metal band-type corrugated clamp coupler (type used to splice lengths of culvert) over the hole (after treating the rust if possible to stop it) then use body filler or epoxy cement to patch the hole in the culvert through to the band clamp. This of course requres full outside access so obviously cannot bedone if the water level cannot be lowered below the culvert inlet level or sandbagged off. Note you need the full culvert weight type - there are thin culvert splice clamps like box stores carry, and then heavy-duty repair type which are full culvert thickness - the former would rust out pretty quickly.

If the water flow velocity is low (just a msall pond, not serving as the outlet for a significant stream, so erosion of the patch is ont a concert, then you could just fill the hole with portland cement/sand or concrete mix (pretreating the rust first) right flush to the hole in the culvert, then use asphalt fibrous roofing patch material to coat the metal (preferably inside and outside to the extent of the eroded hole as well) to limit rusting.

If using a repair band it is a good idea to coat the outside of the culvert around the hole with a gooey layer of the asphalt patch material as well, so the band squeezes down on it as a gasket/sealer so your repair does not leak water out around the outside of the culvert - which in most "pond" situations which were not fully engineered, could result in erosion around the outside of the pipe over time. (Some types of band come with rubber gasket material which also works for this, most do not and the gaskets are pricey.)

Answered 2 years ago by LCD

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