I like concrete. I’m fascinated by it as a material. Ferrocement, Latex Concrete, Fabric formed concrete, Cement putty, fiber reinforced, papercrete…All of it.
Does anyone want to play with it? Explore its potential with me? Maybe a bit of a masonry interest group?
Just seems really hard to work with and I don’t think the space would be very conducive to it with no external water supply. The dust I’d imagine precludes it from indoor use.
I have considered that. What got me rethinking the potential was the trebuchet project and casting the counterweights out of quikcrete. That was a large ish project in my opinion and I figure much of what we’d do would be smaller items. If we did decide on having a little place for concrete storage I think a cart or a space as small as 3’x3’ could contain a bag of sand and cement and maybe a little container of admixture.
I am very much an advocate of safe practices and dust can be a serious factor to mitigate, but other areas of the space generate dust and other particulates and they deal with those in their own way. Foundry and the clay dust in particular was an issue at the ladybird location a few years ago.
This my favorite story about concrete. I use it every time I try to explain my belief that humans forgot very important ancient knowledge during the Dark Ages, and it’s still costing us.
From what I was told, sugar will kill/slow the hardening time in wet concrete. My brothers FIL was a readymix driver. I asked him what they did if they broke down. His response was larger companies carry hoses to hook to another power unit. Smaller companies would carry a 3-5 bag of sugar.
I haven’t ever tried it though.
Sounds like a neat experiment to try.
Working in heavy industry I have seen a lot done with concrete, but it is not my area of expertise.
But there is more than just structural. Malena Skote is a swedish artist who does small items with concrete, I have her book. And Fantastic Ferrocement was written by the guy who built Eutopia in New Zealand, I borrowed that book out and never got it back.
There are lots of neat concrete places in Texas, the monolithic dome institute out in Waxahachie springs to mind. I just want to see the knowledge shared.
Let’s not forget the National Concrete Canoe competition!
http://www.asce.org/event/2017/concrete-canoe/
Not to mention that air particulate hazard monster that exists in Metal Shop called the Sand Blaster… that thing should be cut up and scrapped. I’ve not used a sand blasting cabinet much, but is it “normal” for them to be so “leaky” or is the one in Metal Shop just past it’s prime? If it’s normal, there needs to be a dedicated exhaust hood placed over that thing vented to the outside with a fan that can be set to lift your air to make that thing safe!
Large/small batches can easily be mixed up outside then wheeled into the workshop. Dust issues solved.
Back to topic, I’ve always wondered about soil cement and using calcined gypsum has a hardener. I know it sets up quickly so wondering about experimentation with extenders to give plasticity up to 4-8 hours, giving enough time to pour in molds/forms.
But yah overall, concrete is cool.
Sugar is a retarder. It has other effects and this practice generally won’t fly for structural concrete as an off the cuff admixture. It’s extremely common in oilfield cementing, but the big boys like to call it by a code name so their clients don’t realize they all use the same stuff.
Similarly, table salt (NaCl) is a catalyst – makes it gel faster. Chlorides in cementitious materials is a whole different world of things to talk about.
For any proper concrete work, the batch time is the first check. Too old and it doesn’t get placed. Doesn’t matter if the truck broke down, spec says you only have 90 minutes (typical) in the truck.
Isn’t concrete dust more directly harmful because of the lye? Like chemical burns to the airways and lungs? Saw dust and sand Blaster particulates can cause respiratory problems over time through chronic inflammation, but they don’t typically directly destroy the tissue except over long periods of time.
I would google the MSDS on concrete for more details about limits. But having worked around it for years with no I’ll effects, I wouldn’t worry.
I’ve had holes in blue jeans from quick setting concreted purchased through the typical big box stores. It can be caustic and the lime dust isn’t good for some materials. It’s something that should be mixed outside.
Okay. I generally wore gloves and rubber boots when I was working on slabs. Safety equipment is important. 
I don’t think a little concrete work is going to be too dangerous for the makerspace.
Use a respirator. Silicosis is bad. After mixing airborne dust isn’t a problem, but you’re talking about starting with dry ingredients.
In small batches (nothing you’ll do yourself will ever be a large batch), liquid admixtures are easier to handle, measure, and mix.
I think its various problems can be fixed with proper maintenance and a little member know-how. At one point, the dust collector was 100% full, yet people kept using it anyway.
Wearing a respirator while using the sandblaster is strongly recommended. This is why (after about 30 mins use of DMS blaster):
True, but it also effects every other member in the metal shop. So the one person using the sand blaster and creating a high particulate environment also effects every other member in the shop. Therefore, the member on the plasmacam and the members using the welders and anybody hanging out also have to wear a respirator.
New seals maybe help. In particular the vacuum connection was rather loose I thought.
While I was taking classes over at UT Arlington, I came across one of their concrete canoes. It bore the name “Guppy Gone Bad”
