isolde said:
With my post, I didn't mean intermediate joists - I meant attic joists, which can be insulated on the cold side - because you weren't planning to have parquet up in the cold attic, right? And by saying it gets expensive, I didn't mean the material costs, but the labor costs - it's quicker and less hassle to insulate the attic afterwards.
In one of my above posts, I provide an explanation for why one doesn't insulate intermediate joists.
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Haha, nice maneuver there.Tyresö said:
I don't know where you got cast roof slabs from. They exist in multi-family houses from the 60s (lamella houses), hardly in today's villas. Furthermore, you surely don't seriously think that anyone is interested in underfloor heating in a roof slab? rickardg explicitly writes that he wants to install underfloor heating:
Yes, you can partly do that. Betongbanken.se has a nice picture of a flat panel with cellplast inserts. I attached the same image in my previous post, and another from a large construction where a large part of the concrete is replaced by "bowling balls".rickardg said:
Additionally, I attach another image of a slab construction optimized to save concrete and self-weight. Concrete or ceramic blocks that are used to fill the slab before casting are sealed so that the concrete does not flow in. Just as is done with hollow-core slabs.
Exactly rickardg - you got it. Are you with us, Tyresö?rickardg said:
Thanks for the compliment!isolde said:Haha, nice maneuver there.
I don't know where you got cast wind deck from. They exist in multi-family houses from the 60s (lamellar houses), hardly in today's villas. Additionally, you don't seriously think anyone is interested in underfloor heating in a wind deck, do you? rickardg explicitly writes that he wants to install underfloor heating:
Exactly rickardg - you got the idea. Are you with us, Tyresö?
Yes, wind decks are still being built with both HDF blocks and filigree slabs as you showed in the picture, and that's what I meant.
Also, in my previous posts in the thread, I have mentioned that there's no point in having insulated intermediate joists. It's not necessary - not even if you cast in or in any other way install underfloor heating pipes. There is no total heat loss if the heat is distributed to the upper or lower floor.
I understand what you mean and I understand that you are informed about the issue - it's just that I don't see any point in casting insulation into an intermediate deck.
However, it's common to cast in heating pipes in non-insulated joists, which I understand.
Then a little correction which is not meant badly - the website address is www.betongbanken.com
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Interesting images There seems to be quite a few products on the same theme, most of them however seem to be for thicker joists than what is normally found in houses, but there might be smaller variants (the one with the styrofoam boards looked like it could work on thinner ones even though it seemed to become thick considering the reinforcement), if nothing else, the same type of styrofoam used for ground slabs should work to lay on regular slab joists(?) if you just manage to anchor it properly, have connecting reinforced concrete-filled spaces between the blocks, and someone who knows has calculated it beforehand.
A new question I'm pondering: How do you handle drilling in slab joists and sandwich walls for sewer pipes and ventilation pipes? (thinking of 110mm sewer pipes, and 160, 200, 300mm ventilation pipes). Is the drilling done in the factory or afterwards?
There seems to be quite a few products on the same theme, most of them however seem to be for thicker joists than what is normally found in houses, but there might be smaller variants (the one with the styrofoam boards looked like it could work on thinner ones even though it seemed to become thick considering the reinforcement), if nothing else, the same type of styrofoam used for ground slabs should work to lay on regular slab joists(?) if you just manage to anchor it properly, have connecting reinforced concrete-filled spaces between the blocks, and someone who knows has calculated it beforehand.A new question I'm pondering: How do you handle drilling in slab joists and sandwich walls for sewer pipes and ventilation pipes? (thinking of 110mm sewer pipes, and 160, 200, 300mm ventilation pipes). Is the drilling done in the factory or afterwards?
"rickardg"
My experience is that both are done. It's not holes they make at the prefab factories - they make recesses where the pipes are to be routed, then the holes are sealed again after the pipe installations.
But hole drilling does also occur after the framework is erected.
My experience is that both are done. It's not holes they make at the prefab factories - they make recesses where the pipes are to be routed, then the holes are sealed again after the pipe installations.
But hole drilling does also occur after the framework is erected.
However, I have a question for "Pingen"
Are there any "standard modules" manufactured that are stocked before they are sold, or is everything made to order?
Are there any "standard modules" manufactured that are stocked before they are sold, or is everything made to order?
You others will have to excuse me, but I believe that few here have better knowledge about HD/F floor slabs than I do. In addition to specialist knowledge about HD/F, I have class 1 training (which comes after/above class 2, as illogical as it may seem) in precast concrete. I work at Europe's leading prefab group with 130 factories in 25 countries and 12,000 employees, so I dare to say that we are actually quite good at what we do.
HD/F is cast using a so-called extruder method. Earth-moist concrete is poured into a hopper on a machine, and at the end of the machine, a finished HD/F slab emerges, which already has the strength to walk on (as long as you don't step directly over the channel). Any adjustments to the slab that do not involve cutting the reinforcing wires are made immediately. This can include various hole cuttings or cast-in fittings and other components. After that, the slab is allowed to cure; we have a cycle time of about 7 hours with the help of water curing. Then the 195m long slab in our case is cut into the correct lengths, any slanted ends or narrower slabs are sawed out now. Normally, the slab is now ready for installation.
HD/F is cast using a so-called extruder method. Earth-moist concrete is poured into a hopper on a machine, and at the end of the machine, a finished HD/F slab emerges, which already has the strength to walk on (as long as you don't step directly over the channel). Any adjustments to the slab that do not involve cutting the reinforcing wires are made immediately. This can include various hole cuttings or cast-in fittings and other components. After that, the slab is allowed to cure; we have a cycle time of about 7 hours with the help of water curing. Then the 195m long slab in our case is cut into the correct lengths, any slanted ends or narrower slabs are sawed out now. Normally, the slab is now ready for installation.
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Then I'll take the opportunity to hijack the thread (sorry TS)
I have a question for "JhenrikJ"
Isn't it the same concrete training (class 3 - 2 - 1) for "regular" concrete and precast concrete? Basically, it's the same concrete, just with different mixes.
You might also be able to answer my question in post #21.
I have a question for "JhenrikJ"
Isn't it the same concrete training (class 3 - 2 - 1) for "regular" concrete and precast concrete? Basically, it's the same concrete, just with different mixes.
You might also be able to answer my question in post #21.
No, the training for in-situ concrete and precast concrete is different. The training doesn't just cover the concrete itself; it involves a lot more about the placement of reinforcement according to exposure classes and such. (Actually, concrete manufacturing is a very small part of the course.) What mainly differentiates the trainings is that the on-site builders study form calculations for three days so they can construct molds on site that won't break when the concrete is poured in. In the prefab industry, we don't have that issue because since we cast walls and columns laying down, our molds aren't subjected to the same concrete pressure. The in-situ builders also learn about winter casting, which we don't concern ourselves with (except for our assembly guys who have to take that training).Tyresö said:
I'll get back to you about #21.
Even more OT, but perhaps of interest:Tyresö said:
It is only, if nothing has changed, class 2 and 1 that have an examination.
The course for class 2 qualification is amusingly called the B-course!
To complicate matters further, we must distinguish between concrete manufacturing class and precast concrete execution class. In my case, I am approved for execution class 1 (which is the more important of the two). It doesn't matter how good the concrete is if the person responsible for the construction is not approved for a higher execution class than class 2, then it will just be a class 2 building anyway....
There were a few things I thought about when reading this thread, such as whether it's possible to increase the tensile strength in concrete and how often metal fibers are used as reinforcement in prefabricated elements, or if it's usually just bars that are used?
And then I thought after seeing a certain type of slab, why concrete isn't used only for the load-bearing part so it becomes something like the second image in post 15 here. I was thinking more if it would work with a mesh-reinforced slab, which is then welded/tied into a truss with, say, a U profile at the end where you can attach a wooden beam to screw the ceiling into, so that the total height is about 5 times higher than the cast slab, as it should be significantly better than having a solid slab considering weight and tensile strength, or am I completely wrong there?
Then I'm not sure if this becomes a general question about concrete, but anyway, I'm wondering what the difference is between concrete with fine materials like stone dust or say 0-4mm or 4-8mm gravel compared to 16-32, which seems to be quite common size, so a fine mix fills up better and should need less mortar than a coarse one. But how does it affect the water-cement ratio (WCR), and how is the tensile strength affected, both in terms of compression and tension, and is the bond strength also affected when it should grip the reinforcement?
And one last question now is why so much is cast on-site today, since it should be cheaper to buy prefabricated elements than to do it yourself on-site, or are the elements so expensive that it balances out to set up forms and handle reinforcement yourself? And isn't it much easier to do the job lying down, and don't you risk the cement and aggregate separating, or maybe that's the wrong choice of words, but I was thinking that one comes to the bottom and the other to the top, resulting in different tensile strengths vertically if you vibrate a tall casting? I thought it would be easier to make prefabricated elements on-site in something like a tent and in metal forms, rather than building new wooden forms for each casting and then erecting them when you get there instead of building everything from scratch and then waiting for it to set so they can proceed with the next layer without bursting the form due to the cement pressure when casting high things?
It feels easier to weld together some forms to have a batch of concrete and then cast those elements when it's time, and if you have about 3-4 different elements that you'll use for most things and need approximately the same number of each, you can just keep casting in those forms and set aside the ones not needed at the moment, and just take them out when you get to the part where they're required. Or you could build forms out of wood and have the workers construct them in a warm tent protected from rain and snow, so it becomes like prefabrication, but each form is custom-sized according to what's needed as there might be many different blocks in a house, especially if we are talking about villas or houses with many distinctive features.
Some thoughts, and hoping for some answers too
And then I thought after seeing a certain type of slab, why concrete isn't used only for the load-bearing part so it becomes something like the second image in post 15 here. I was thinking more if it would work with a mesh-reinforced slab, which is then welded/tied into a truss with, say, a U profile at the end where you can attach a wooden beam to screw the ceiling into, so that the total height is about 5 times higher than the cast slab, as it should be significantly better than having a solid slab considering weight and tensile strength, or am I completely wrong there?
Then I'm not sure if this becomes a general question about concrete, but anyway, I'm wondering what the difference is between concrete with fine materials like stone dust or say 0-4mm or 4-8mm gravel compared to 16-32, which seems to be quite common size, so a fine mix fills up better and should need less mortar than a coarse one. But how does it affect the water-cement ratio (WCR), and how is the tensile strength affected, both in terms of compression and tension, and is the bond strength also affected when it should grip the reinforcement?
And one last question now is why so much is cast on-site today, since it should be cheaper to buy prefabricated elements than to do it yourself on-site, or are the elements so expensive that it balances out to set up forms and handle reinforcement yourself? And isn't it much easier to do the job lying down, and don't you risk the cement and aggregate separating, or maybe that's the wrong choice of words, but I was thinking that one comes to the bottom and the other to the top, resulting in different tensile strengths vertically if you vibrate a tall casting? I thought it would be easier to make prefabricated elements on-site in something like a tent and in metal forms, rather than building new wooden forms for each casting and then erecting them when you get there instead of building everything from scratch and then waiting for it to set so they can proceed with the next layer without bursting the form due to the cement pressure when casting high things?
It feels easier to weld together some forms to have a batch of concrete and then cast those elements when it's time, and if you have about 3-4 different elements that you'll use for most things and need approximately the same number of each, you can just keep casting in those forms and set aside the ones not needed at the moment, and just take them out when you get to the part where they're required. Or you could build forms out of wood and have the workers construct them in a warm tent protected from rain and snow, so it becomes like prefabrication, but each form is custom-sized according to what's needed as there might be many different blocks in a house, especially if we are talking about villas or houses with many distinctive features.
Some thoughts, and hoping for some answers too
Not sure I understand this part of the question?miry said:
But if you're looking into how concrete is affected by the size of the aggregate, the relationship is that the finer
(smaller) the grains, the lower the strength at the same cement amount.
At the same time, the consistency becomes stiffer with the same amount of water.
Therefore, it is usually aimed to have as coarse aggregate as is practically possible.
Form execution, reinforcement density, processing, and possible pumping are factors that can determine the size.
What I was thinking was that if you increase the mantle surface of the ballast, the cement has more space to adhere to and should then get a higher tensile strength, and if you use something like 4-8mm ballast, less cement is required to make it even, so if you mix in as much cement as with coarse ballast, it should become stronger (higher K-value). What I find worst about concrete is that it has such poor tensile strength, so it cracks under a bending moment if you haven't reinforced enough, and it can be a bit tricky to calculate how dense you should lay it and how coarse the reinforcement needs to be so that the cracks don't get too large, causing the steel to rust after it has cracked, or should you calculate to prevent cracking on prefab as it becomes unnecessary to reinforce it and it won't withstand much then.anaitis said: