Making Wall Caps

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Old 03-13-13, 11:54 AM
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Making Wall Caps

Hi,

Soon will be building about 200' of retaining wall using concrete blocks.

The top caps are unusually expensive (150%+) more than the block and they aren't too attractive with sharp edges and flat on top.

Have the time and inclination to build my own top caps but wondering about the mix and materials.

I want to make them 1 1/4" thick at the narrowest (slight dome) with 1 part Portland and 2 1/2 - 3 parts sand. I understand the mix is correct according to a book I have.

Please verify the mix and the big question is: Can I use the sand I have on my land? I am in Central Florida and have areas where it is "pure" sugar sand which would be very convenient not to mention, cheaper. Can strain the sand for any debris (leaves, twigs) but the sand is generally very "clean".

Will appreciate some experienced advice.....Thanks
 
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Old 03-13-13, 09:14 PM
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I would never use a mortar mix to construct a wall cap, as mortar doesn't have the structural integrity that concrete does. You need rock in the mix for the strength required to resist weathering stresses and abrasion. I'd also suspect local sand might contain enough salt to be detrimental to any mortar/concrete mix.

But I'd also be leery of building any kind of retaining wall more than a course or two high using concrete blocks. You are talking about CMUs (having void cells), yes, and not solid paver blocks? If the wall is tall and has any kind of loads behind it, your plan should include doweling vertical rebar into the footing the blocks will be laid on, and possibly either filling all voids with concrete or building pilasters every 10' or so. Instead of CMUs, I'd use paver blocks myself, as they come in many attractive finishes, and are very durable and simple to install. Look especially nice if a few sweeping curves are incorporated into the design.
 
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Old 03-14-13, 05:34 AM
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How tall will the block wall be? What's on the other side of the retaining wall? I used to live in Orange county and everything is fairly flat. The footer doesn't need to be deep but does need to be about 2' wide. I've used sugar sand on small projects and it seemed to do ok - don't know if there are any long term ill effects from using it.
 
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Old 03-14-13, 05:45 AM
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The caps I have seen being made have used a normal concrete mix and usually include a couple sticks of rebar or other reinforcement. Most often I've seen the forms made of wood. They build in a draft angle so there are no true verticals. There is always a bit of taper to help to cap come out of the mold. The mold is painted or sprayed with a release agent to further help the cap come out of the mold. In Central America they use diesel or kerosene.
 
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