I bought a diamond cup grinding wheel for my 4.5" grinder to remove an acrylic stained concrete finish. The cup works great removing the acrylic stain, but it leaves the concrete highly polished and slippery. Is there a particular grinding wheel that will leave a no-slip, coarse concrete surface?
Concrete – Are there diamond cup grinder wheels that create a coarse, no slip concrete surface
concretefinishgrinderpaint-removal
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I don't think you'd want to use salt for a couple of reasons:
- if you have any rebar in there, salt will increase corrosion
- salt will affect the concrete mix, possibly badly affecting strength
Instead, use one of the polymer grip additives designed for this purpose - they can be very cheap, and some are transparent so do not affect the appearance of the concrete.
An example - I haven't used this one, but there are many available.
Concrete is an wonderfully easy product to shape. For your scenario, all you really need is make a form for the concrete that matches the concavity of your drain, and to set it in place when you place the concrete.
It's not clear when you say curved if the drain itself curves along its length or if by curve you refer to the concave portion of the drain.
If your drain is basically straight with a concave portion, the problem is very easy - PVC drain pipe of the appropriate diameter, plugged tight with rags and capped off with duct tape will do the trick nicely.
If your drain itself curves, you'll have to get more creative in making a form - possibly shaping one from wood.
Regardless of the shape, in this scenario you will want to suspend the form from above, so build a series of wooden supports and put hooks in the top of the form in a clean straight line and tie each hook to a frame so that the form hangs ROUGLY halfway into the trough when the frame is set over it.
You must also make sure that the form is lowest wherever the water is to exit the trough and highest at the trough's ends, so that water will flow properly in the trough. A 1/8" drop per linear foot of trough should suffice.
What you want is a form that from its end looks like this picture, and which has the slightest tilt to it to make the water run downhill in the trough in the proper places.
(Ground - brown, frame - red, form - grey, black - line suspending form to frame)
Once your form is ready, move it out of the way, mix your concrete and fill the trough up until the concrete is high enough that the form will set down into it some. Make sure there are no air gaps in the concrete so far.
Put the form in place, carefully making sure it settles into the concrete to the proper depth (ie: the suspending wire is taut). Now fill the rest of the trough's sides with concrete until its just level with the soil.
Wait until the concrete begins to set. When you can push on the concrete with your finger and not easily make a dent, remove the form, and use a wet sponge to clean up the edges where you removed it.
Viola - a concrete drain with concave drain channel!
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Best Answer
Short answer: no, at least if used as intended.
There are some cups and disks that are extremely coarse; they look like a few pebbles of abrasive stuck in random spots. But they just remove more material faster, and still leave a surface smoother than would be helpful for your purpose. The problem is the rotation and speed. The abrasive gets at the whole surface with just a little motion of the grinder.
You could do something different with a coarse cup. Hold the grinder in one spot and turn it on for just a second or so. It will grind a circle in that spot. Move the grinder to another spot and repeat. The idea is to cover the concrete with a pattern of circles. They don't need to be deep, maybe on the order of 1/16".
Another technique is to use a circular saw with a diamond cutting wheel. Adjust the blade guide so the cutting depth is very shallow (around 1/16"), and use a guide to make straight grooves at controlled locations. Grooves about 1" apart should be enough.
You could also try the opposite approach; add instead of remove. Bond a thin layer on top with a broomed finish (you would need material with high bonding strength designed for this purpose). There are also surface finishes that contain some coarse grit for traction. Or you can buy non-slip tape sold for this purpose. It is a rugged tape with a gritty surface and a serious adhesive. You put down strips about 9" apart.