Mini Concrete Blocks - All Weather Building!

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Introduction: Mini Concrete Blocks - All Weather Building!

About: I'm a Product Design Engineer, currently living in the UK. I have been fortunate to have lived, studied and worked in Hong Kong, Norway and California. I believe physical models help people to communicate, d…

This is going to sound like a variant of the 3-Little Pigs / Big Bad Wolf fable...
You've played with plastic Duplo Bricks (but you're supposed to keep them indoors);
You're played with wooden Building Blocks (but these don't like getting soaked in water/mud);
And now you crave the full outdoor, all-weather, bespoke experience!
Now you need to level-up to mini-concrete Blocks (for the aspiring Bob The Builder in your or your child!).

Perhaps a tad over-dramatic, but in all honesty, this was where I found necessity to be the mother of invention: I spent forever washing the mud off Duplo Brick my son played with outside in the dirt, picking the bits from the crevices, and of course the wooden blocks if not dried properly actually go mouldy. Even when you put them in the washing machine, it's ok, but not ideal.

We had played with 'full size' building bricks, but this required considerable supervision, as my Son was able to stack them high enough to potentially fall over and hurt himself! So I hit upon the idea of making them smaller, but with all the outdoor durability of real bricks, and also as a 'rugged' play experience, it is fun to give kids an atypical material or product to engage with. Kids seem endlessly fascinated to emulate 'grown-up' things, and from my time working in the Toy Industry, I've come to believe that the trick is to 'scale it down', and to make affordances so they can interact, (rather than to 'dumb it down'), whenever it is possible (safety, cost, etc.).

In this guide, I go through the steps to making some nice little concrete bricks by making your own moulds. I especially like the notion that you can create your own designs and shapes, and that with a little engineering knowledge of the material, you'll be able to get more confident and ambitious!

For the Teachers out there, I know the physics of 'keystones' and arches still seem to be on the curriculum for many schools, and this would be a great classroom project to trial variations to find the perfect keystone angles/geometry.


Disclaimer: Every effort has been made to make this a 'common sense' and safe guide, but I can't accept responsibility for any harm or damage caused by following this guide. Please do realise that the bricks are heavy, and if thrown will hurt others, or smash things like glass, etc. I do not advise leaving your child unattended with these bricks. And please do inspect them for wear and tear, as they do contain metal mesh inside, which if exposed will be sharp, (and may rust / degrade over time and use).
Counterpoint: That said, if you want to evaluate the risk of such play / toys like this, do also check out: Reggio Amelia, who among other things, champion the notion that kids learn through getting hands-on, dirty, and the occasional bump - and are on the whole, better for it. As well as this notable mini Documentary on Danish Kids Who Play With Knives. The choice is yours. Be safe. Have fun.

Supplies

Essentials:
Cement: https://amzn.to/3eklmWd (though I'd get from a DIY store!), along with Sand & Gravel.
Plastic Adhesive (UHU or SuperGlue).
ABS Plastic (or you can use card): https://amzn.to/3uvo3Ji
Bucket, Stick for Mixing, Gloves and Goggles (when mixing and pouring).


Optional:
Wire Mesh: https://amzn.to/3tv4zEg
Snips: https://amzn.to/3o5xcqn

Step 1: Early Mud House Technology

The back-story of this project came from days out playing by a riverbed. Between the litter, and fly-tipping, there was some great adventures to be had - one being making clay (from riverbed silt), and this in term lead to making a 'Mud House', as shown in the first picture.

I was reminded of how much I enjoyed doing this when I was a kid, and so much of the fun is the rhythm and process, of mixing, spreading, laying stones/bricks, repeat....

...and of course, the tension of not knowing when it might fall over. Did you build too fast, too wet/dry, could the shapes tesselate better, does it need more binder (grass), or more sand for internal friction?

All these things seem to happen, without needing to say a word. As kids, we seem to 'absorb' this tacit awareness of the world around us, simply by doing.

As it happens, this came full-circle, and we used mud and the fabricated concrete blocks to make some really robust buildings....more on that later, but for now - on with the Instructable!

Step 2: Score 'n' Snap - Working With Plastic Sheet.

I use 2mm ABS Sheet, as it is easy to cut using a knife and a ruler. You do not even need a saw or rotary tool - and it gives a clean finish...

Start by marking out the 'side' of the dimension of the brick you want to make.

(I've always tried to make life easy, and avoid copious measurements, so here I just used the width of the metal ruler (about 25mm/1"). I scored a series of lines in the sheet.). I suggest about 2-3 scores per line.

Then I scored perpendicular to this, this time about 75mm / 3" long (these I did mark), and others 40mm / 1.5". From this 'grid', you will find you can simply bend and snap the plastic into the required sides.

This should give you batches of 2x 40x25mm and 2x 75x40mm pieces.


If you want more detail on this, I have guides here (LINK).

And also a video showing how to do it (LINK).

Step 3: Easy Peasy

I wanted to show how after all the scalpel-work is done, even a 4 year-old can snap the plastic.

If it's too difficult, I suggest pre-scoring a little deeper, but this can be done, once you have the hang of it.

Step 4: Creating the Profiles

A bit like a 'cookie cutter', you need to create the perimeter for the brick-moulds. I did this by using sticky tape. This is a surprisingly good material, as it has a little elasticity, and holds the shape in tension.

Stick the sides and ends together as shown, ready for the bases...


Safety Note: As can be seen from images, I do worth with knives around my Son, but never unsupervised. I would advise you use your own judgement here, if they can be trusted not to touch. If in doubt, keep out of reach.

Step 5: Glue the Bases

I applied the same 'score and snap' technique, and used this to create a series of rectangles to fit the base...(ie 75+2+2mm by 40+2+2mm), so a 79x44mm section. If you don't want to be this accurate, you can simply cut them 'oversize', and this is fine also (you'll see I've done this with some later on!)

I then applied Superglue to the corners, and left to dry fully.


I did do this part on my own, (ie my Son was having lunch), as Superglue is beyond my level of risk:reward! If I had wanted him to participate, I'd have used a less rapid glue like UHU, and of course googles.

Step 6: All-Sorts

All ready to go with the glue thoroughly dry.

If you want to also play with curved shapes, you can do forms like this, either by bending by hand, or if you like you can warm the plastic with a heat-gun, or a hot hairdryer. Again, another reason I find this material very fast to work with. More here (LINK).

Step 7: Keystones & Bridges

As mentioned in the pre-amble/intro - if you wanted to experiment with these shapes, this was a nice trick, and also shows a more efficient way to mould even the 'straight' bricks, as it uses both sides for moulding!

I began by folding a sheet of A4 paper some 4 times, and then cutting out a basic keystone shape from the stack of paper to get 16 identical shapes.

I was then able to 'test' how big the arch would be (see second picture), and this seemed a good form. (If you're not happy with it, regroup the templates, and cut a more acute angle on each side.

I then took these paper templates, and laid them head-to-toe, as shown in the third image, and marked the positions, before arranging as shown. Safe to say, the top and bottom sides are from one long strip of plastic.

It's worth noting that the vertical joins are not glued, and are left free. This is to allow the mould to 'flex', so as to release the bricks when dry. (If you glue all sides, this will make it hard to remove). However, do glue the 'bottom' edges to the base.

Note these are done in single 'strips', so as to allow easy flexing to release the bricks.

Step 8: Steel Reinforcement

In all honesty, this was me getting slightly carried away. It's true this certainly makes some of the long bricks much stronger, but it's not critical for the 'normal' 75x40mm bricks!

I happened to have some left over from another project, so this was not an 'expense', but you can use any other wire placed laterally on long bricks. Though I'd suggest adding kinks to it to give the concrete more to 'grab'.

I confess, I was too 'hands full' with concrete, and kiddo, to also take pictures, but the trick is to pour in half full, drop in a piece of mesh, and top up. Job done!

Step 9: Mini Cement Mixer!

So this is just huge fun for kids! All the play of sandcastles - but with a 'cooking' aspect to measuring out quantities, and mixing to a given consistency.

I used 1 part Portland Fast Dry Cement, 3 Parts Sand, and 4 Parts Aggregate - as this was what was on the pack, but you should follow what your supplier advises on the pack. I used a plantpot as the 'unit' / part, as this was easy to for my son to handle, despite the holes!

I'm not going to write a blow-by-blow guide on this, as firstly, it's hard to do it whilst holding a phone, covered in dirt, and watching kiddo, but also because Instructables wrote the guide I was using anyway!

>> Concrete Class: https://www.instructables.com/Concrete-Class/

Safe to say you want a consistency which is not so liquid it's sloppy, but no thick it does not 'tamp' down and flow. If you're unsure - mix up a mini batch first.

Step 10: Pour & Tamp

Here's the filled 'Keystone' bricks.

They look 'shiny' / wet on top, because firstly I smoothed them out with the trowel, but secondly I 'tamped' them on the table to release air, and excess water rises to the top.

Once dry, depending on the weather and the type of cement you have, they can be released when 'set', but still moist to touch. This is fine, but be aware that they are weaker, and benefit from more time to dry. But if you're confident not to break them, it means you can speed up production. I found after some 2 repeats, I was able to de-mould after 1 hour on a warm day.

NOTE: As much as you might think heat helps - drying too rapidly is not good for concrete, so oddly if it's really hot, place in shade.

Step 11: De-Mould

My description perhaps makes sense now - as you can see here, the mould can 'flex' and allow the Bricks to be easily removed, for both the rectangular bricks, and the keystone variety.

It depends how gentle you are, and how much glue you applied, but if the sides snap off, it's totally fine, and you just tape/glue them back again for the next moulding session.

I got easily 6-7 repetitions out of each mould (I have loads of bricks now!), and they would have kept on going too. Highly re-usable. I kept them for any future projects, but you can also recycle ABS.

Step 12: Production Line

I placed the 'wet' bricks to finish curing / drying, on a well ventilated table.

As can be seen, the bricks took on quite a lot of the detail, even the glue over-spill in places, so in hindsight, I think I should have made a 3D printed (inverted) logo or name on these! Hope you can do this. Perhaps even Blu-tak, Clay or Plasticine will work fine?? Please share if you do!

Step 13: Let the Building Commence!

This was a really fun project, to do with my Son, but also to then step-back and allow him to build some crazy creations of his own.

True to expectation / design - it has rained, snowed, and had sun on for some time now, and the bricks have held up well to all the elements, as well as wear and tear from paying with friends too!

Step 14: Keystone Kids

As mentioned, the keystone bricks worked very nicely - both functioning as good stacking bricks for walls, but also providing a tricky but fun challenge to assemble (with only two hands).

I have not tried painting the bricks yet, but this strikes me as an easy thing to do, and will probably be quite fun. You can also buy pigments for concrete, but I found these unreasonably expensive for a project this small and casual, but if you can get a mini quantity, perhaps you can try adding colours too!

You may also see I used toilet tubes and yoghurt pots to also make unusual bricks - so have fun, and try out different shapes and materials...

Hope you like it, and thanks for sharing any variations you make!

Step 15: Mud 'Mortar' & Mini Bricks

The great thing about concrete is that it 'sucks' moisture up, so much that mud can be used like 'mortar' to glue bricks together, and they can even support their own weight!

And make precarious leaning towers.

Safe to say, they come clean through soaking / scrubbing in a bucket of water (or a puddle!!).

Step 16: Outdoor Games & Obstacle Courses

They can be combined with offcuts of wood, to make a bridge as shown here - to span a puddle, in games or with plastic toys!

This was when our local park football field was flooded...sometimes you find unusual games in the mot unlikely of situations!

Step 17: Creative Toys and Role Play Games

Other kids in the park also wanted to join in, and created homes, games, and all sorts of other things using the bricks. This is what some play specialists call a 'play starter', in that [a brick] is not in and of itself that special, but it becomes something simple enough to get ideas started, and then once going, it recedes, and more and more novel elements some into play.

I love how this brick house, had grown beyond the obvious, to have 'trees', and even a 'bath' (made from a plastic bag) were 'invented' by the kids, as well as many stories and role play games.

---

Please share what you enjoy making with these mini building bricks.

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    47 Comments

    0
    AntAfrica
    AntAfrica

    16 days ago

    I love this idea. Especially as you added some creative ways of using them too.
    Well done!

    0
    DavidW742
    DavidW742

    24 days ago

    We will of course require an upgrade to our bolly truck to transport these to the park, and back. Absolutely delightful and lovely photographs.

    0
    pemazzei
    pemazzei

    27 days ago

    Hello. Very nice! I liked the "mini cement mixer".!!Do you know if we can use steel wires in the corners? Paulo, Brazil

    0
    Hey Jude
    Hey Jude

    Reply 26 days ago

    Hello in Brazil - very cool! Hope you'r doing ok. I have friends there, and it sounds intense to say the least. As for the mixer - yeah, I am wondering about this =)
    As for reinforcement - many things will work, and cable ties, paper clips, etc. will likely be ok. I think as long as you keep the tips 'inside' the brick would be my advice.

    0
    pemazzei
    pemazzei

    Reply 26 days ago

    Hello, não sabia que voce fala português! posso fazer perguntas em pórtuguês? Grato, Paulo

    0
    Hey Jude
    Hey Jude

    Reply 25 days ago

    Não. Desculpe. Apenas Google Translate. Mas ok para fazer perguntas!

    0
    pemazzei
    pemazzei

    Reply 25 days ago

    OK, thanks. Paulo

    0
    dkistner
    dkistner

    27 days ago

    I wonder if hypertufa would work as well. It would be lighter, allowing for making bricks that are a little bigger, but the question would be if they would be heavy enough to stay stacked. If somebody does make hypertufa bricks, please post!

    0
    Hey Jude
    Hey Jude

    Reply 26 days ago

    This is coooooool. Never heard of this. I'm reluctant to dig up moss, but I like the idea of it, and wonder if I can think of a less 'eco important' substitute. I suspect dried grass cuttings will not be very structural, but please do have a google around and let me know if you have any good finds!
    I found this: https://empressofdirt.net/make-hypertufa-pots/

    0
    dkistner
    dkistner

    Reply 25 days ago

    You don't have to use moss. People who make hypertufa troughs usually mix some moss with yogurt and paint it on the planter so it'll grow moss on the sides. The basic recipe can be made with coir instead of peat moss, and coir is sustainable. Of the second ingredient Empress of Dirt mentions, sand is the strongest and heaviest and least porous (used a lot for stepping stones along with a bit of that fiber fortifier stuff); perlite is the lightest, but pieces are more prone to weathering out on the outside, leaving little holes; and vermiculite is, to me, the best of both worlds: both lighter weight and a smoother surface and just a nicer finish all around. There are plenty of recipes online, some using less portland cement, and which you try will depend on the strength needed.

    0
    Hey Jude
    Hey Jude

    Reply 25 days ago

    Oh great - I have Vermiculite from my gardening efforts - didn't now I could use this! I'll have to give that a go. What's the best Ratio (ie max) do you reckon? I realise the answer is perhaps 'trial and error', but any tips welcome if you've done it before (e.g. perhaps pre-soak the Vermiculite?).

    0
    dkistner
    dkistner

    Reply 25 days ago

    The basic recipe is simple: 1 part Portland cement, 1 part vermiculite (or perlite or sand), 1 part screened peat moss or coir. Mix all together dry, then add water slowly until of the consistency you would normally mix concrete. You could certainly try dry grass clippings instead of vermiculite, but start with vermiculite and see how you like it. Google hypertufa and you'll find all kinds of things people do with it, creative ways they carve and shape it in the green stage, etc. Just be sure to cure it well before putting stress on it.

    Download this: https://www.bluefoxfarm.com/support-files/hypertufa-how-to-manual.pdf

    Note that the recipe used here is a four-part recipe. There's more info on how to do it in this PDF. Have fun!

    0
    SimB3
    SimB3

    27 days ago

    Great idea; great execution.

    0
    Hey Jude
    Hey Jude

    Reply 25 days ago

    Thanks so much!

    0
    LeslieGeee
    LeslieGeee

    27 days ago

    LOL first thing I thought about ( having had kids ) was one getting angry and throwing a cement building block at the other. Great idea but maybe fill the center with something light such as polly pellets or the like( bean bag filler ). Also putting the fear of Mom or Dad into them by instructing that these will not be thrown. Sometimes ya got to get into the mud to think like a kid lol.

    0
    Hey Jude
    Hey Jude

    Reply 26 days ago

    Yep - hence the disclaimer. But then the 'risk' is as same as having rocks at the beach, right? I had certainly wondered about additives, but polystyrene is tricky as it floats, so it's be an uneven distribution. Any suggestions welcome tho! I think lighter would be good to 'crack' as a challenge. =D

    0
    LeslieGeee
    LeslieGeee

    Reply 26 days ago

    Hi Jude, You are right polystyrene does float, and rocks can be thrown. I was thinking the outside rim of cement might be heavy enough. The other thing I was thinking on was to make a hollow center to the blocks that way the kids can put tiny decorations like pebbles and sticks and flowers in. You can add fiberglass filament to strengthen the cement. Or cut smaller shapes of heavy duty screening and press into the cement front and back for reinforcement. I am suggesting the type of screening that is cat claw proof. The other thing may be to use a super fine cement like Rapid Set and paint the outside of simply made taped cardboard shapes or make blocks of appliance packing the kind that protects the appliance so that the block is basically "hollow" inside. Styrofoam can be used too but a sheet can be expensive, Maybe the pink craft foam that you can get at Home Depot or Lowes. Just cut the shape out with a knife or box cutter.Also sand down edges of so as not to be so sharp. Ok that is my last two cents, I can't turn up a think tank type situation. Your Idea is still a good one :) I also like the fact that you let your kid (s) play in the mud LOL.
    rapid set cement all

    0
    Hey Jude
    Hey Jude

    Reply 25 days ago

    Hi Leslie,
    Thanks for your reply. I actually see a fair bit of yellow insulation, and I guess the floating issue might still be a factor, but then, it's perhaps worth a shot, and one could even do two pours perhaps? Hmmmm. Wonder how well Concrete bonds to itself...I could add all manner of metal 'ties' but this is getting elaborate perhaps with minimal gains in less weight? Afterall, one would need at least 10mm thickness around the brick to be strong, which for a 25x40x75mm (75,000mm^3) brick would mean a 5x20x55mm (5,500mm^3) 'core'...so this would at best a 7% reduction in mass. So I think probably it'd come down to an aggregate that is lighter rather than a core perhaps? What do you think?

    0
    Anybody1
    Anybody1

    27 days ago

    Please provide another link to the ABS plastic. This one goes to a cement page. Thanks.