Thought about something.
If you cast a concrete column, or concrete wall, or concrete footing, for example, it should (or even must?) be reinforced.
But if you instead build with leca blocks or concrete hollow blocks or similar blocks, there is no vertical reinforcement. Usually, reinforcement is placed every third layer, but that is a horizontal reinforcement and doesn't do much good for vertical forces.
At the same time, leca blocks are very fragile compared to concrete, which is much more durable. Despite this, concrete is reinforced?
As an example, the following is stated in the wood guide:
"2. Basement wall of concrete or lightweight concrete blocks, alternatively cast-in-place reinforced concrete."
Source: https://www.traguiden.se/konstruktion/konstruktionsexempel/grundlaggning/kallargrund/principlosning/
So if a basement wall, or even a column of leca blocks, manages without the material being reinforced, why wouldn't concrete withstand it, which is actually even stronger?
One thought I have is that the joints absorb movements and therefore prevent the blocks from cracking, but on the other hand, it doesn't feel like a total guarantee, and yet most houses with basement walls of leca blocks or similar blocks, or for example "homemade" columns of leca blocks, etc., withstand large loads.
If you cast a concrete column, or concrete wall, or concrete footing, for example, it should (or even must?) be reinforced.
But if you instead build with leca blocks or concrete hollow blocks or similar blocks, there is no vertical reinforcement. Usually, reinforcement is placed every third layer, but that is a horizontal reinforcement and doesn't do much good for vertical forces.
At the same time, leca blocks are very fragile compared to concrete, which is much more durable. Despite this, concrete is reinforced?
As an example, the following is stated in the wood guide:
"2. Basement wall of concrete or lightweight concrete blocks, alternatively cast-in-place reinforced concrete."
Source: https://www.traguiden.se/konstruktion/konstruktionsexempel/grundlaggning/kallargrund/principlosning/
So if a basement wall, or even a column of leca blocks, manages without the material being reinforced, why wouldn't concrete withstand it, which is actually even stronger?
One thought I have is that the joints absorb movements and therefore prevent the blocks from cracking, but on the other hand, it doesn't feel like a total guarantee, and yet most houses with basement walls of leca blocks or similar blocks, or for example "homemade" columns of leca blocks, etc., withstand large loads.
Reinforcement is used to absorb tensile forces. Concrete/Leca is good at compressive forces but poor at tensile ones. When casting concrete, vertical reinforcement is used because it strengthens against tensile forces/stresses. Vertical reinforcement doesn't work with masonry, so only horizontal reinforcement is used to absorb bending loads on the wall (lateral forces).
Moreover, masonry structures require transverse walls (bracing) with not too large distances. The higher the walls, the shorter the distance between the bracings.
In addition to the above excellent post, I would like to say that the comparison becomes interesting only when you reach greater heights. You can build reinforced concrete columns that are very tall, which is not possible with lecablock or concrete hollow blocks. The reinforcement is needed to prevent bending/buckling. A 70 cm concrete plinth does not need reinforcement.
L largab said:
But as per the example I quoted in my first post, they write "cast in place reinforced concrete."B bossespecial said:
But if we now compare the same type of construction, i.e., a basement wall with the same number of transverse, bracing, walls.
We build one with masonry Lecablocks and the other as a cast-in-place concrete wall without reinforcement.
Shouldn't the concrete wall still be stronger, despite the lack of reinforcement? Or?
J justusandersson said:
So a 70 cm high concrete column, with a footprint of, well, say 20x20 cm for example, which is part of a building structure, say one of the columns for a crawl space (so it is loaded by a building).J justusandersson said:
Such a column does not need reinforcement and will hold without cracking under the construction?
But where is the threshold for when reinforcement needs to be used?
Because I still seem to read about how important reinforcement is, but at the same time, constructions are made with Lecablocks, which feel much more fragile than concrete, without these Lecablock constructions collapsing like a house of cards.
Note, when it comes to beams, it's, of course, a different matter, because then we are talking about tensile forces, so there reinforcement is necessary. My questions and examples are now solely about compressive forces.
Yes, unreinforced concrete is much stronger than masonry leca blocks, but more importantly, it is also stiffer. This means that if the concrete is subjected to small movements (e.g., settling), the stresses in the concrete become greater.
This will lead to cracks (where there are tensile forces).
Concrete is better at handling tensile forces than masonry leca blocks. This means that the crack spacing becomes large and thereby the crack width as well.
This will lead to cracks (where there are tensile forces).
Concrete is better at handling tensile forces than masonry leca blocks. This means that the crack spacing becomes large and thereby the crack width as well.
Can you then say that a foundation foot, or basement wall, made of lecablocks is a safer construction than the same construction with unreinforced concrete?harry73 said:
If you have a column with a large load on it, the column becomes shorter. But as the column becomes shorter, it also becomes wider. When this happens, all sorts of stresses arise in the material, including tensile stresses that cause the concrete to break. Reinforcement can absorb these stresses, allowing the concrete to withstand a greater load.Martin_B said:
If you made the same column out of lecablock, it would break much sooner.
I would think so, then the reinforcement becomes more important with the height. There are many unreinforced concrete roads that work without problems.
Then I could imagine that if you were to, for example, cast pillars, you could make the construction more resistant to movements and thereby also "stronger" or at least safer, by casting a piece up, placing sliding layers in between, casting another piece, sliding layers again, etc. So it becomes a bit like masonry blocks.
I have seen extensions on houses where the extension itself is built as an open crawl space, meaning you can see underneath. And the extension stands on lecablock, at a few points, maybe 1.5 m between the lecablocks. In one case, the extension is even 1.5 stories. I don't understand how the 1.5-story extension hasn't collapsed because the leca has cracked. Or is it a given that the leca can handle this?
Most materials can withstand quite significant compressive forces if they are not too high. Beams subjected to bending forces are considerably more sensitive.
A wooden structure doesn't weigh that much
No, that's true. But do you mean that the concrete can withstand the compressive strength indicated on, for example, pre-mixed concrete bags, without reinforcement?
Well, yes, it technically can. But that's assuming everything stays perfectly still. However, any minor movement would cause the concrete to crack and the structure above to collapse? (In the worst case)
Sorry for the silly questions, but I'm trying to understand how it all fits together
No, a crack in the concrete does not cause the house to collapse. And it would probably be possible to build house walls in unreinforced concrete, but the walls would be thicker than reinforced concrete.