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The poor man's sand binder
vtsteam:
:thumbup: Thank you!
Sand pits around here seem to be all mixed sedimentary stuff and coarse grains.
Maybe I'll start looking further afield.
ironman:
vtsteam Here are two photos of sand grains. Quarry sand is the sand I use and the pro sand is a sample of graded sand a friend gave me. Also have a look at this video it shows portland cement being used the same way I use graphite on my cores.
vtsteam:
Great photos, and a really wonderful movie. Thank you Ironman!
I think what you have as quarry sand would be called "sharp sand" here. Both samples look to be nearly entirely quartz (silica) sand. I'm going to have to hunt for a source for that. I'll post pix of what is commonly found here for sand.
That movie was really fascinating. Tough though. No shoes pouring and on shakeout. But amazing work. With dirt. Pulling those handle patterns, wood fired aluminum melter (I was just mentioning wanting to build such a thing in another thread).
Now that dirt was very fine -- detail was amazing -- the lettering, etc. Nice work with the spoon!
That movie was something....
Thank you again!
vtsteam:
Back to original topic I thought I'd try making some cores using a different cement -- Rockite -- readily available in small quantities here at hardware stores. Saves having to buy a 94 lb bag of Portland.
The last time I tried this I used some of a used bag of Portland I had in storage of uncertain date. Probably not fresh enough.
The Rockite is nice because it comes in a small box with a plastic bag sealed with a rubber band inside, and I can keep it indoors, out of the damp barn.
Anyway, used ironman's 9% cement 4% water mix with sand. The first core came out nice and firm and clean -- not sandy/crumbly like my last effort. However it did break into 3 pieces in getting it out of the PVC pipe core box. It Probably weak layers from uneven ramming -- I could see the sand was more open grained at the breaks. This is a pretty long core, so maybe that's also the problem.
It might have held together if I'd embedded a length of wire as reinforcement. I have another one to unmold -- I'll wait another day to see if that helps.
Otherwise I think it's good. Haven't tried to
ironman:
The smallest core I make is 19mm (3/4") dia. The core would always come out in one piece but would have 100% failure rate when poured in iron. I fixed the breakage problem by using a wire to strengthen the core.
That rockite looks like could be very useful because it sets faster than Portland cement. Does it set in one hour like label says?
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