concrete headwall for tinhorn

RxRatedZ71 · Sep 9, 2013

Has anyone ever constructed a concrete headwall for a tinhorn? I've got an 18" tinhorn that is at the end of a 800' dowhill drainage ditch that dumps into my creek. The water has caused the end of the bank to slough off and into the creek. We have put in a 24' tinhorn and are building the area back up, but I need to build the headwall to direct the water into the pipe. Here's a pic of the horn and then a pic of the downhill slope towards the pipe.

RxRatedZ71 · Sep 9, 2013

Here is an idea of what I'm trying to construct. I've thought about just pouring the walls and then the front apron area separate. Then I've also thought about trying to design the forms in place such that I could pour the concrete into the walls and then pour it out front and do one large monolithic pour with rebar throughout. According to my measurements, I think I could get in and out for less than 1 cu.yd. on the walls and then a 4-6" thick apron in the front. I thought about 8" thick walls, 3' tall by 4' wide back wall, and then 18" wide by 4' tall wing walls. Should the wing walls slope of taper downward? Any advantage to that other than less concrete? Would it be better to pour a footer/base with the steel already in it and then pour the walls after the fact?

MarkV · Sep 10, 2013

Have you considered using bags of ready mix concrete dry stacked and then staked with rebar? The bags will set up with ground moisture and I see a good many of those around here that have been there for years. Seems like a quick economical way to go if you don't need the esthetics where it will be placed.

MarkV

DJ54 · Sep 10, 2013

We normally poured the footers & aprons first, leaving upright stubs of re-bar to tie onto for the walls. Footers were poured oversize on the backside to allow for short pins sticking out of the concrete to hold the bottom of the forms, basically something to kick back against. This is done on the front side too, and just nip the pins off flush on the front side when your done. You need to figure the width of your wall + the thickness of you form(s) (we used panels built from 2 X 4's and 3/4" plywood. Then allowed more room for wedges cut approx. 1' long made from 4" X 4" cut diagonally. Pieces of scrap 2 X 4 were used as spacers inside the form to get your proper and even width. These were just temporary, and pulled as the concrete was poured. With the spacers inserted, the wedges were tapped in to hold in place, and a couple of spikes nailed through the wedge to keep them from moving. Using the wedges simply allows you to have room to release the form to remove.

2 X 4's spiked across the top to hold the form together, usually with spacers above the form to allow to get a nice finish. Then wedged kickers into the bank on the front & back to keep it upright, and in place.

Height & width of the headwall, and taper of the wingwalls mostly depended on the slope of the bank. I am assuming you keep this mowed, so you need to keep that type of maintenance in mind. Some gravel placed behind the headwall on top of the footer, acting as a french drain, will allow trapped water to get out, and prevent a lot of hoving outward from freezing temps.

Also on the outlet end, I would suggest over digging, and placing a large type of rock to keep the water from scouring back under the pipe.

The concrete will probably have to be poured a little wet to get it to conform to the pipe. You'll probably have to do a little chouncing as we called it to work the concrete around it. We had vibrators to do this. Also, if your having the concrete brought in by truck, have him drop it right on top of the pipe, not to the side. Rushing concrete will force the pipe & form up, if it hits it at the right angle..!!

RxRatedZ71 · Sep 10, 2013

Thanks for that feedback. I built the forms using 1" thick plywood, scrap 2x4s and 1x4s. I typically screw the boards together so I can then just unscrew select parts and take the forms out in large pieces.
I spent this AM trimming the forms down to a more practical size . I think I know how I plan on placing the rebar so as to maximize strength. I will be mixing the concrete by hand. Seems to have worked for me in the past, but I've never poured a wall either. I can typically pour 3 bags about every 10min while I have someone working the concrete in the forms. Once its setup, the screws can be removed and the forms taken apart. Any small holes can usually be worked back to smooth. Ill keep you posted of my progress...

RxRatedZ71 · Sep 16, 2013

Got head wall formed up and in place a few days ago.

We bought a pallet of Quicrete (42 bags) and got to work on the mixing.I ended up forming the endwall and poured it a few hours later. Im gonna be sore tomorrow.

We had a semi-load of material brought out to use for filling around the tinhorn and walls. They call it "back wash" and get it from drilling sites as a waste product. They say it sets up better than clay and has great holding power. It has round river rocks, sand, and clay balls in it. Its heavy stuff; my loader could barely lift a full bucket of it.