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Posted by DanG on October 15, 2006, 10:23 am
You had shown us examples of super smooth concrete caps earlier.
These are a bit rougher with a split face look on the outside
edges to boot.
Are you just looking for basically a flat top square/rectangle
with fractured look edges about 2" thick? You can go for the
fractured edge as you describe, but I would cast a few extras.
Concrete often doesn't like to break where you intend. You might
consider creating the rough edge in your form work. The other cap
stones you show, do not look slick finished to me; I think if you
cast them on a masonite surface they will be way too smooth to
blend with what you have going. I think I would consider using
an oversized plywood base, create the rough edge with fractured
Styrofoam or eat the edges with a solvent. Cast and vibrate as
described. The squares ( they look like you headed for about
30"x30") are large enough to warrant some hog wire reinforcement.
They are not thick enough for rebar and I don't think 6/6 x 10/10
mesh will help enough. The finish looks like something you could
get by acid etching the formed surfaces and power washing. Your
existing caps don't have the shiny look of cast concrete.
______________________________
Keep the whole world singing . . . .
DanG (remove the sevens)
dgriff237@7cox.net
> Good morning.
>
> This is a follow-up to my original concrete casting question,
> detailing what I am actually up to. I would appreciate any
> advice you can offer.
>
> Thanks
> -Mark
>
> http://www.canleyworks.com/temp/pier_caps/
>
> My "Pisa" block piers need caps!
>
> The standard caps are too small. . .I would need to assemble
> caps
> out of at least seven mitered pieces, which is not the look I
> want.
> So my plan is to pour caps large enough to complete the piers.
> My plan is as follows:
>
> 1. Build a form. Use masonite or melamine to create a smooth top
> surface, and wood or rubber trim to create the beveled edges.
> The bevels would actually form a channel where a brick chisel
> will be used on the finished product to strike off the outer
> two inches or so, creating a broken edge to match the standard
> caps.
> The mould would include bevels on the upper side of the mould as
> well,
> aligned with the bevels on the bottom. This forms the "pinch
> point"
> where the edges will eventually be stuck off.
>
> Should the block be reinforced? Rebar, or screen?
>
> 2. Through experimentation, arrive at a color mix that
> reasonably
> approximates the factory-made blocks. A separate color mix would
> be used
> to create the streaks of contrasting color that run through the
> blocks.
>
> 3. Mix the concrete. I plan to use a cement-heavy mix (formula
> suggestions?),
> and screen the pea gravel to remove aggregate larger than 1/4"
> or so.
> Larger aggregate doesn't look good when the edge is broken off.
> Include the coloring in the mix.
>
> 4. When the mix is ready, sprinkle the accent color over the
> concrete and
> fold it in. Repeat once or twice. Don't over-mix.
>
> 5. Treat mould with release compound (suggestions?). Pour the
> concrete
> into the mould and vibrate the mould with my rotary hammer.
>
> 6. Remove finished block from mould. Allow to harden for a week
> or so,
> then chisel off the edges. Install on piers. Celebrate.
>
>
>
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