I was researching polyester resin for coating concrete and came upon an interesting article that delved into the use of epoxy resins as mortar to replace damaged and worn concrete structures. It became obvious that salts and naturally occurring toxins will deteriorate concrete and that bonding any materials together, even like materials, creates problems that aren’t initially obvious to builders and designers. Here the article titles, “Durability of Concrete Structures: Investigation, Repair, Protection”
The problems that are discussed in this article are far beyond the level of engineering exactness that I need for my artwork projects making photo fresco pieces, but these problems sounded similar in theory to the issues that I have been considering with my work which can be reviewed at: PhotoFresco.blogspot.com
Lately I have been working with cement versus plaster and I am attracted to the cement because of the potential durability of the material for exterior use, versus the plaster materials that weather quicker when used outside. I’ve been mixing a wide range of cement, mortars and grouts to try and find a material that is affordable and durable, but I keep coming back to the idea that polyester resins or epoxy sealers offer a strong layer of protection from the elements. My latest effort has included mixing iron particles or atomized steel powder into the resin and then painting it on the top of some hybrid cement brick pattern panels. Ideally the polyester resin will bond to the dried cement and the atomized steel will protect the resin from uv and the usual suspects like salts that are in water that will break down and wear away cement. The real reason for the iron particles is that I also like the effect of rusted metal and hope to imitate that effect once I find a final use for the panels.
The real issue is similar to what some of the problems are that were discussed in the article I linked above and I still have my reservations about this coating technique in that the cement may continue to shrink over time as it releases any water that is still in it and the polyester resins, which also shrink when they are setting may eventually release from the cement and crack away from the underlay. Although the polyester resin may appear like a paint when I am putting it on, it is basically a plastic shell that hardens into the crevices and cracks of the cement. If either of the two materials shrink or expand over time, which they will, then that will cause them to possibly break their bond. Any movement won’t be the same for the widely different materials, so as one my shrink at a slow rate the other may shrink quicker on a microscopic level and when they expand then both may expand to different degrees.
I would like to say that in reading some sections in the article above it sounded like spraying the layers, which would result in thinner applications, was a logical step that developed over some time as repairs to concrete structures were made. This may be consistent with my process of applying a very thin coat, veneer, or gel coat of the resin in that the layer is not so thick as to cause cracking during the initial set up phase when applied on top of concrete. Essentially it is the same as painting the rock, but with the goal fo a deeper penetration with the polyester resin, so I hope that the thin layers will hold, but only time will tell. Later I will apply a light coat of acid to facilitate the oxidation of the top coat, like a quick rust effect, so I hope that any cracking or breakage will occur quickly too so that I don’t waste too much time if this isn’t going to pan out. My goal would be to have a quick weathering machine that could imitate 100 or 200 years of weathering in a single night, then I would have a better idea of how this stuff will last. My current weathering machine is to just throw things into the yard and check on them after each storm.
More can be found at PhotoFresco.com