Anybody know where I can find Portland Type I cement for making aragocrete?  The Home Depot.�s and such seem to only carry the Type I/II.

The type I/II works great too, In fact under identical conditions it will achieve higher strength with less free lime than the type I. But if you really want the white it can be had at concrete solutions, 3596 so. 500 w.

You can get pigments there too if you're interested in trying color.

Thanks so much for the info Chris, I really appreciate it!  Are you still using the same recipe that you posted in October of 2004?  Have you tweaked anything?

Here's the simple skinny, 5 parts coarse aggregate (3/8" to 1/8" type crushed coral) 2 parts fine aggregate (seafloor grade or equivalent sand) 2 to 3 parts Cement (grey type I/II, white type I, brown type III, whatever) 1. prewet everything (bowls, tools, casting medium, aggregates) 2. mix all materials till cement coats all particles evenly 3. add water slowly until cement is just saturated (rice krispy treat consistence) 4. wet slightly more to facilitate easier shaping 5. cast as desired ensuring good particle contact in the piece 6. cover cast well to prevent drying 7. strip in 12-24 hours and get into freshwater to continue cement hydration 8. cure in freshwater for 8 weeks, changing water frequently especially in the first week or two. 9. Enjoy your DIY Reef structure TIPS WEAR GLOVES, cement is fairly caustic when first mixed Fill size gaps, try for some aggregates in all size ranges for best balance of  strength and void space volume. saturate aggregates and casting medium ahead of time for easy use when needed

Thanks for finding and reposting that, I'd been looking for a way to put the recipe out there in a simple form. I had forgotten that I'd done that once already.

That recipe is still pretty much the ratios I work with. I sort of cook by feel, adding cement, sand, and coarse aggregate till it has the texture I'm going for, and a good coating of cement on all particles.

The easiest way to cast and get interesting forms, I find, is to use a bucket or suitable container and put a little of my wetted aggregate in the bottom. Then drop in some clumps of aragocrete mix, then pour more wetted aggs. around it, then more 'crete lumps so that they touch the others, then more fill, more 'crete, and so on till youve formed a layered, random, shape you like. Try not to pack the 'crete as you do this, other than a bit of squishing into the other lumps, so as not to press out desireale voids. Then tap the bucket or whatever rapidly but lightly to create vibration which will better bond the particles of cement together and to the aggregates. The more you do this the stronger your casting will be but you will start shaking out bubbles (read: voids) so don't overdo, thirty seconds or so should give a solid piece.

Start with small batches and experiment with it to get what you like out of it. You'll quickly get a feel for it I'm sure, but if you'd like a demonstration, or just a casting buddy to B.S. with while we mix, You're welcome to come by and see what I do, I cast whenever I can get an excuse to.

Actually I should say, after the concrete is properly MIXED and cured, ....

thouroughly blending the dry pigment into the dry cement before mixing will ensure proper impregnation.