Hello. My first post, hoping I can utelise your extensive knowledge.
Im trying to cast individual flagstones out of concrete with metal work (aluminium or steel) about 5mm below the surface. The idea is that eventually the top layer or concrete will be worn down by foot fall thus exposing the metal work below. Here is an images of some tests I have done:
I would like to do two different versions, one that can be worn away with sand paper/wet-and-dry, to show the effect. The other would be the actual piece, with the correct mix design to work as a paving slab.
My problem is that I can't find the correct mix to acheive these properties. The concrete is either too soft and crumbly, or too hard to polish/abrade. The aggeragte also tends to crumble out of the surface instead of being worn along with the concrete.
Thank you for any help you can be of, and if you know of any links or people I should email I would be very greatful if you would let me know.
what happens to steel when it rusts?
to be honest david the kind of info you need would come from a doctor of metalurgy or summat like that,there is a couple of guys here who manafacture slabs ,but i doubt they will be willing to share their R and D information with ya
i have tried casting stuff myself a few times and it normally goes wrong due to aggregate size or cement content etc
good luck with your slabs
LLL
I'm not too worried about the metal work, as I can always switch to stainless steel or aluminium to avoid rust. Its just getting the right mix design and size/type of aggregate to avoid crumbly and air-pocketed slabs.
you need to speak to mouldmaker or look through the thread in the craic called "my patio/terrace" a book called concrete in the home
by Fu-Tung Cheng is mentioned.
good luck
LLL
I've seen this kind of thing done before, I think with Brass patterns inlaid. I believe the top surface was ground/polished back to expose the brasswork. The drawback to having a concrete mix that will wear down relatively quickly with foot traffic is that it will fall apart, or keep on wearing so that the exposed steelwork will become a trip hazard rather than a feature. Either way I can't see how this would be of any benefit, all you can do is show the buyer a picture and say "This is what your slab may look like eventually"!
The other alternative is to clamp the steelwork hard against the face of the mould so it's exposed from the outset. Mix design isn't much of a problem.
