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tamp in & wash out
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This is a great idea!! Next time one of my driveways turns out like this, I'll be quick to point out the aesthetics of that look....
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I've seen this finish a lot in newer construction in the San Francisco Bay area. I figured it was for extra traction since it rains a fair amount in the winter. Almost never freezes.
*Sorry;yes, this is in the land of "never freezes". San francisco to sacramento valley. Also used it in the sierra foothills where you get frost, even snow, but really no hard freezes.A
*The reason rock salt is used is that it won't dissolve on contact with the damp concrete. The purpose is to create voids in the surface for a textured look. Hosing it down after the concrete is set dissolves the rock and leaves the void. The salt does not eat the concrete. One reason that concrete spalls is not due to salt, it is due to the increased amount of freeze/thaw cycles the concrete goes through when salt is applied. If the concrete is not air-entrained it does not contain the microscopic air pockets necessary to allow freezing (read expanding) water a place to expand to. Thus the saturated area spalls. Another reason is the "baptism" of a fresh slab during the finishing. Most good mix designs have enough water in them to finish without the addition of water on the surface. This reduces the water/cement ratio on the surface where it is most critical. The third major reason is also attributed to poor finishing. When using non-air entrained concrete (never a good idea when exposed to weather) the floated slab must sit until the bleed-water comes to the surface and starts to evaporate. If the surface is sealed before the bleed water is out, it is trapped below the surface and will cause delamination of the surface. Concrete is a simple material. It does, however, require a substantial amount of work to be done properly. This is apparently something that is not stressed in current apprenticeship programs or is deprogrammed in the field. A good finisher is worth what ever he/she asks. A bad one is more expensive!
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I just did a rock salt finish walkway 2 months ago. It's sooo easy to do & with the concrete colored, it is a very nice finish. What I found most apealing about it was the fact that the finish to the concrete was less than perfect before applying the salt & this gave it a kind of tile or semi-smooth clay texture. We left some of the swirls & small ridges left by the "cream", & this along with the pitting really give the "natural" or "weathered" look.
Ken
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i have some colored concrete patios requiring a salt finish and was looking for any advice or tips on the application of the salt and method of tamping it in to the surface or just sprinkling it on.
*Is this a regional thing? In the midwest we try to keep salt away from concrete, unless you want the pitted look :)
*Yes, what is this salt finish? please explain.
*Season to taste.:-)Rich (not helpful) Beckman
*tamp in & wash out
*hello calvin, salt finsh is a pocked type random texture. we use rock salt and you just broadcast it onto the troweled concrete, kind of like feeding a chicken, then you tamp it in and let the salt eat a little hole in the top of the slab. the next day you wash out the salt so you don't scuff up your new finish. happy building !!!
*I've done it two ways:Small patios: Knee boards, go around and pound it in with a wood float.Driveways: Big roller fits on the bull float handle.Both; just get it down flush. Don't put it on when there is any water on the surface.Also, I create a 6" wide strip around the edges with an edger, and give it a brush finish, don't salt this. Nice pattern, kind of frames it. (Can also do the opposite, brush the center and salt the edges. Lazier)
*These salt finish slabs in the warm weather country? No danger of peeling later? It still amazes me how you can learn something everyday. Damn.