[Note - I had a good look around and couldn’t find this anywhere. All I could find was bricks with keyed surfaces for good rendering bond strength].

Regular cement blocks for building construction, however with a keyed fitment profile on top and end surfaces, ie steps in the casting so adjacent/on top blocks fit together neatly rather than just on top of each other. Several key advantages –

1) Better joint strength because any shear or bending failure will have to break out the overlapping lips, and the mortar will have a larger surface area for bonding.

2) More consistent laying because blocks will fit together neatly rather than just butted against each other with a supposedly even mortar layer, leading to –

3) much less mortar needed as it is now purely a glue rather than a gap filler. I would imagine you could use a few millimetres of mortar, in fact you might want to apply mortar differently because of how thin it is now. Maybe even sprayed on, or [8th]’s self-amalgamating mortar would be better. Or maybe use an actual glue rather than mortar….
-- Custardguts, May 03 2016

Self Amalgamating Concrete Self-amalgamating_20concrete
A good way to do the mortar.... [Custardguts, May 03 2016]

Halfbakery: Cusquenian Concrete Cusquenian Concrete
It's only inferred in the idea, but keyed blocks was kind of where I was going with this one. [zen_tom, May 03 2016]

Eddystone Lightouse https://en.wikipedi...iki/Smeaton's_Tower
In particular, the image under 'Construction' [TomP, May 03 2016]

Baked: https://www.youtube...watch?v=QI6rkH2QELE
This isn't the only style of this I've seen, either - some look like big two-dot Lego. [elhigh, May 11 2016]

Making keyed bricks https://www.youtube...watch?v=Xk67L6FAQvo
Concrete and soil bricks used in Africa [popbottle, Apr 16 2017]

Mortar IS glue, for stone-ish substances
-- Vernon, May 03 2016


//Mortar IS glue// Not really. The right mortar will have some stiction to the right blocks, but it's not much. Lime mortar (used in many buildings that have stood for several centuries) has almost no stiction; and modern cement mortars have low stiction to soft brick. The tensile strength of mortar is never factored into calculations of structural strength.
-- MaxwellBuchanan, May 03 2016


Yeah I think we could go a bit higher in tensile/shear strength than regular mortar. I mean if the tolerances were tight enough you could use a relatively small volume of a high strength filled epoxy and add a huge amount of strength to the structure, especially with the lapped keyed connections I'm talking about.

Thanks for the link [zen] - I didn't spot your previous idea. I was thinking less about lots of custom shapes, more along the lines of every block is the exact same shape to keep the cost down; just toe out at the bottom, toe in at the top, and toe out on left hand end, toe in the other, with defined inside and outside surfaces. You'd still end up with smooth flat inside and outside surfaces, just the interlock between blocks has a step in it. Probably need special corner blocks too, I dunno, I'd have to think my way around a few corners etc to be sure but I bet you could get away with as little as 3 or 4 unique moldings, and mostly just one. You wouldn't be able to use 1/3 bricks for weird lengths etc without doing something tricky.

I wonder if doing this could cut down on core filling and ties for cyclone rated areas (where you have to actually hold the roof down...)?
-- Custardguts, May 03 2016


Yes, I was thinking of custom-shaped blocks in my earlier idea, but it makes a lot more sense to have a modular solution that gets applied on site to multiple buildings.
-- zen_tom, May 03 2016


Is this a proposal for giant Lego?
-- mitxela, May 03 2016


I'm disappointed no one has suggested these be Penrose bricks
-- hippo, May 03 2016


Mr. Smeeton baked this in the Eddystone Lighthouse [link].
-- TomP, May 03 2016


[mix] - kinda but not really; like lego but without the interference fit, with some lateral fit as well as vertical, made out of cement rather than plastic, and glued together.

I saw ideas about giant lego. This isn't really giant lego.
-- Custardguts, May 03 2016


If you google "Porotherm bricks" the're clearly keyed in a very mild sense.

The brick is a pretty remarkable bit of technology. Most shocking is the total lack of innovation through its very long history. We worked out that they got stronger if you baked them about 5000 years ago, after that... we messed about with color and holes a bit. I'm unsure whether this lack of development is really just the brick continuously developing into the same thing, or if there's just no appetite for change in what most see as a mundane object.

When you play about with a variety of key types... you do start to run into problems. I first considered a ridge on top, down the length and a matching hollow in the bottom of the brick. Works great for a straight wall, doesn't work well for corners, joining two layers (headers and stretchers), slight bends, they don't alternate-stack on a palate for stability and the lowest brick might need an insert underneath for strength.

OK, so, how about the lengthways hollow on the bottom and two bumps on top? If you space the bumps right, now they key parallel and perpendicular and you can make headers and stretchers work. Corners work, and you have enough wiggle room to make walls bend. They end up looking like 2-bump lego bricks. You still need to think about the top and bottom layers, no matter what you do, you end up losing versatility... which is probably the point.
-- bs0u0155, May 03 2016


It's moving away from the keying aspect, but what about a series of tetrominoid shapes that increase intra-brickular cohesion through presenting surface-to-surface contacts in more than one plane?
-- zen_tom, May 03 2016


I've seen a few different examples along these lines in developing countries, always the goal is to minimize the expensive ingredients. The usual goal is to make use of ready labor, cheap materials (dirt) stabilized with a modicum of cement and needing little expertise to build.
-- elhigh, May 11 2016


Could this idea be useful for space-age construction in places such as O'Neill cylinders, where the Coriolis force has to be considered when building a building?
-- Wrongfellow, Apr 16 2017



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