April is the Concrete Month…

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April is the Concrete Month…

…breeding projects out of the dead rock, mixing
Portland cement and aggregate, stirring
Dry gravel with spring rain.

Or something like that. Anyway, I promise that our materials Skill Builder unit for this month will be much more fun than The Waste Land. As hard as it may be to even imagine that much fun in one place.

During April, we are spotlighting one of humanity’s oldest, cheapest, and most commonly-used building materials—also, surprisingly, one of its most poorly understood. Speaking generally, concrete is a mixture of three components: aggregate, cement, and water. The aggregate can be gravel, sand, glass, plastic, chunks of old concrete, or pretty much any other solid filler. Concrete’s characteristic transformation—from wet slurry or paste to hard, rock-like solid—depends on the reaction between cement and water, a chemical process known as hydration.

But the number of variables involved in the process of mixing and forming a particular batch of concrete is surprisingly large, and the structure of bulk concrete, at the atomic and molecular level, is wonderfully complex. Scientists are just now beginning to understand it. And while we can’t hope to even touch on every aspect of the subject in a single month, we can, hopefully, show you something you haven’t seen before, and maybe even inspire you to make something concrete, yourself. Stay tuned!

P.S. As always, if you’ve seen a project or a maker doing something inspiring with our featured material, please do let us know, below. Thanks!

44 thoughts on “April is the Concrete Month…

  1. Jimmy P says:

    I would like to see information on concrete that is filled with many air pockets – ways to produce light, insulating, concrete blocks that are still structurally sound. Is there are a way to chemically or pneumatically introduce tiny air pockets during the curing process?

    1. Bryan K says:


      I’m building a DIY pizza oven, and there is a lot of emphasis on thermally-enhanced concrete for things like the hearth slab and the oven covering. One common method is to add vermiculite or pearlite in high doses (I’ve seen 5-1 and up to 12-1 ratios). These low density “gravels” enhance thermal insulation a great deal in concrete.


      1. Bryan K says:

        *Perlite (not pearlite the steel phase)

    2. MSilvia says:

      This isn’t an established technique by any means, and it may not be practical, but if you mixed the concrete with gaseous water (carbonated for example, though dissolved Argon and the like might be better insulators) in a high-pressure environment and depressurized it at the right point during curing, dissolved gas in the water should come out of solution (the same effect as opening a shaken can of soda) and be trapped in the concrete. Of course, expansion of the material’s dimensions could be an issue.

    3. Khan says:

      Aluminum reacts with lime during curing to make the Aerocrete type products.

  2. Khan says:

    I am also excited about concrete month. I hope they cover a way to great silica fume with out having to buy a pallet at a time. Oh and FRC and cloth/fabric forming!

  3. rocketguy1701 says:

    Concrete recycling is pretty important, as it’s one of the largest CO2 producing processes on the planet (within the category of construction). Reuse as aggregate seems to be pretty doable.

    I’d like to see some concrete countertop articles, dealing with fiber reinforcement, low-aggregate mixes, embedding objects/fiber optics etc. Should also bring back the post about the glow-in-the-dark aggregate (I think it was the CCAC materials library article), I actually used it for my master bath concrete floor, and it’s pretty awesome. No need for a nightlight at 2am. I was surprised how hard the plastic was, but of course it makes sense, if it flexes, it will pop out eventually.

  4. Rick F says:

    I’d like to add to the earlier comment about the interest in refractory cement used in high-heat applications mentioned earlier. I’d love to build some replacement parts for my ceramic BBQ as the company is out of business. I’ve seen projects on the web where you build molds using a form of rubber and then the rubber mold is re-used to create a chamber with which to cast copies of the original item.. Please do something on the chemistry behind refactory cements!?!?!? PLEASE!

  5. Jorge says:

    ASCE’s concrete canoe competition is pretty cool. In college, teams built objects out of concrete: bowling ball, freesbe and the canoe! That would be a good Make article!

  6. Wilt says:

    My friend Eric Billig here in Austin, TX makes so many amazing things out of concrete. You can check him out at http://www.ericbillig.com Below is a link to a bench he made by casting into a tufted cushion or couch. It’s really cool. He’s a real innovator and has done lots of interesting stuff casting into fabric.


    He’s also taught lots of great classes for Austin Tinkering School.

  7. Chris Locke says:

    It’s probably old news, but I’m making cast concrete “fossils” from extinct technology.

  8. Brandon Gore says:

    A recent coffee table I made with cast in saucers – meet ‘THE ORSON’:


    1. April Brooks says:

      Amazing as always Brandon!

    2. Khan says:

      Y’all’s work is fantastic. If have been a fan for a while. I can’t wait until I can justify coming out for one of the courses.

    3. Jerrad Inlow says:


    4. Jack-Lori Smithson says:

      The King!!!

  9. Jerrad Inlow says:

    Here is some of our commercial work that you may have tread on or stood next to without even knowing –


    1. Jack-Lori Smithson says:

      Great work Jerrad! True artisanship!

  10. Damon says:

    In awe of the many creative uses of concrete above. Ongoing concrete-inspired contest going on at: http://www.facebook.com/events/211282582310436/

  11. Jack-Lori Smithson says:

    Concrete is an incredible medium. It never ceases to amaze me and I learn from it every time I work with it… Here is a fireplace surround I made out of GFRC….

  12. Brandon Gore says:

    Fabric-forming is my specialty, the following link is a photo of a sink made attendees of my last 3.5 Fabric-Forming + GFRC Workshop: http://www.facebook.com/photo.php?fbid=10150626490641463&l=ddf7809119

    If anyone is interested in these workshops feel free to check out http://www.GFRCworkshop.com

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I am descended from 5,000 generations of tool-using primates. Also, I went to college and stuff. I am a long-time contributor to MAKE magazine and makezine.com. My work has also appeared in ReadyMade, c't – Magazin für Computertechnik, and The Wall Street Journal.

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