Aerated concrete in uk 2

[Alistair_Heaton]

https://www.theguardian.com/educati...o-be-at-risk-of-collapse-as-concrete-crumbles

Personally I had never heard of the stuff until I started looking at building a workshop.

It has some brilliant properties, but admit the more I digged into it the more involved it was designing with it and onsite compliance with plans.

Locally to me builders really don't want to change their methods. Or materials used. The sites I have seen using it they all seem to use black bar reinforcement. Which is a huge no no. The architects also seem love to pour c20 to fill gaps which messes with the weight loading and gives dissimilar stress concentrations.

Code wise it's lumped in with general construction codes. Australia seems to have a sub set for it.

I have found you need to think of the stuff as a bath sponge. And you need to design round moisture transport, letting it breath and move. Here they cover the stuff with moisture barrier or some other form of barrier which stops evaporation off its surface. Then it just loads up with water. As it's 80% air it's no wonder things fail when it doubles in weight.

 

[LittleInch]

I saw that and was thinking of posting it.

The chickens are coming home to roost on that material alright.

Could be a huge cost to replace all these buildings with it and I think at least 5 major hospitals are impacted.

What was that other concrete disaster? High Alumina Cement?


As ever, look after it properly and it's OK. Ignore maintenence and allow water to penetrate and it will fail.

That manual you had on the bauroc? material was quite complex about how to let it dry out or protect it.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Alistair_Heaton]

There is another on going issue in Ireland with dodgy sand used. Maybe that is what you are referring to.

You wouldn't believe the push back I have been getting from builders and architecs is utterly mind blowing about following that manual and the Australian building codes with it.

 

[LittleInch]

HAC was an issue in the 1970s when a school roof collapsed.

Not surprised you are getting resistance. Builders don't like new things.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

For usually good reasons.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[Alistair_Heaton]

This case I am pretty sure it's them not buying into it and wanting to treat it same as c25.

 

[Alistair_Heaton]

I didn't realise how common it is to completely ignore any requirements on approved drawings.

 

[phamENG]

I didn't realise how common it is to completely ignore any requirements on approved drawings.

In the Eastern US....about 90% of all residential construction ignores requirements on approved drawings. Some are worse than others. I love the ones that frame the entire 3 story building and then ask "what structural drawings?"

 

[jayrod12]

"what structural drawings?"

I've been there too, especially in residential.

Contractor: Good Morning Mr. jayrod12, we're running into some fit up issues in this area here.
Me: Ok, let's go to drawing sheet S5.3 where I've shown sections and plan details of how that complicated corner is intended on being framed.
Contractor: Oh, I don't seem to have that drawing around.
Me: Do you have any of the structural drawings, the overall framing plan on S2.3 clearly has section marks and call offs for details on sheet S5.3.
Contractor: I'm going to be honest with you, I haven't seen your drawings at all.

THEN HOW THE HELL ARE YOU FRAMING THIS THING?!?

 

[Alistair_Heaton]

The only reason why my workshop is being built as per design is because I lifted every single block.

Which resulted in 4mm vertical with 14 rows.

Zero thermal bridges.

I really don't understand the whole nonsense of of building control structural sign off etc when it just going to be built how the builder wants to do it

 

[phamENG]

I really don't understand the whole nonsense of of building control structural sign off etc when it just going to be built how the builder wants to do it

Depends. Sometimes they do it because they think they can get away with it. Some contractors are just that disorganized. Structural design drawings aren't always required, so they grab the architecturals from the office and they're off to the races. The stories I have are when they didn't get away with it. I usually find out because the building inspector shows up with my plans in hand, see's they don't match the construction, and then rejects the work. Sadly they never tell the contractor to fix it, they just tell them to get an engineer to say it's okay as is. Which makes me look like the bad guy when I tell them they can pay me to redesign the building and maybe they can keep some of their work, or they can just go back and build it as designed.

 

[NorthCivil]

I still see aerated concrete around, but never for primary structures. cladding panels, fire walls, curbs/nibs, miscellaneous concrete work.

it has its place but should never be put in a precarious duty: it should never hold up anything important, or be hanging high above ground

 

[Alistair_Heaton]

You can use it for primary load structures it's just you have to use for the whole structure.

You certainly can't use it for all load bearing walls then use normal hollow concrete floor panels.

They come in minimum 330 kg/M2

My aerated comes in at 220 kg/M2 on delivery but then goes down to less than 180kg when it drys out.

My blocks are 1.8 MPA and I can get 5kn/m2 on the floor since I use aerated. If I had used hollow concrete it would have gone down to 1.5.

Just looked a my project calcs it arrives with 35% -40% moisture by weight. After a year without being sealed it's down to 5%. Sealed after 3 years it's still above 10%.

It's 80% air by volume. Which can be filled with moisture. Although it will start disintegrating at 60% according to Australian codes.

 

[Alistair_Heaton]

Just for info for those that haven't see a design manual for the stuff.

This is the one that I used building my workshop.

And I will be using the bauroc render on the outside along with the paint they mention.

Inside walls will have primer and left open. Floor will have crematic tiles upper surface and open on the lower.

https://bauroc.ch/uploads/sites/19/2019/06/bauroc-manual-EN.pdf

 

[dik]

Thanks Alistair...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Pud]

Is this the stuff?

Wallsend school shuts after structural problems found -

https://www.bbc.co.uk/news/uk-england-tyne-65918707

Politicians like to panic, they need activity. It is their substitute for achievement.

 

[Alistair_Heaton]

Yep that's the stuff.

They used it for roofs and then treated them as normal roofs.

Also they went cheap with black bar reinforcement.

The stuff transports water and oxygen. From what can tell black bar has basically a 5 year lifespan when used and a water leak occurs.

All the locals round me told be black bar normal rebar was good enough and the manuals are wrong. I couldn't actually source zn rebar so used mufor A40 wire mesh and ZN threaded rod with 50mm connecting nuts zn.

The mesh is 3 times more expensive but it took 15mins to put in with a staple gun every 4th row. Instead of cutting grooves then fill with mortar. Which would have taken a couple to 3 hours at 30 an hour labour. Which made it way cheaper.

One discussion with architect I asked have you actually read the design manual?

He started squirming and dodge answering. He is now fired.

 

[Alistair_Heaton]

I might add it's thermal properties make it worth the effort for me.

But the utter ball ache of enforcement of material requirements is basically a on going utter fight which involves swearing in multiple languages and firing people and basically being extremely proactive in site supervision.

I am a labourer most days, but every day I catch something that would really screw things up and would be a serious PIA to rectify.

The local building company has reported me 4 times now.. as the site is 50 km from the base and nobody else is using them in the area. They really don't want my build to work.

 

[Alistair_Heaton]

Here is the dodgy sand issue in Ireland I mentioned.

https://www.thejournal.ie/mica-explainer-5467214-Jun2021/

 

[dik]

Thanks Alistair... sand is generally a silica product and quite a bit different than muscovite mica. Muscovite mica can be present in the sand partiles (sand is just a different size of 'rock'). Muscovite mica is a different type of material and is deleterious to concrete. It may also be present in the aggregate.

I'm not sure, but I've heard the 1% can reduce concrete strength by 5% (something I've heard, but have not read and confirmed). Because it is a 'flaky' material and has distinct 'shear' planes it also seriously affect the bond strength. I think the thin flakes can be only a few angstroms thick (from geological engineering courses of 50 years back, so subject to memory lapses).

https://uwaterloo.ca/wat-on-earth/news/mica

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik