Tiling project - advice sought

59 Floride (sold) said:
It's not the concrete that degrades as much as the reinforcement that holds it all together. The Egyptions used concrete but it was da Vincie who invented reinforced concrete. That was the game changer and the principle has been in development ever since. Check out the link below re concrete cancer, that is the limiting factor with concrete. In these days of careful scrutiny and engineer inspections the concrete structures generally last longer than ever, but I would opine that it's land availability and prices that limit the service life of a concrete building.

https://partridge.com.au/concrete-cancer-what-is-it-and-what-does-it-mean/
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Our Italian neighbour was a building Forman on large building sites.
He told me in Italy they had to put all reinforcement steel through a cement slurry making sure it was all coated.
This is not practicing here and he said it makes concrete cancer more likely and starting sooner🤷‍♂️
When he built his house he sure didn’t just chuck rusty steel in
 
I have copies of Vitruvius' books, both in Latin and in English with a description of Roman practice. I simplified, but basically, add water to some material from near Naples and you have a cement. I think the simplification is OK for the forum.

Alkaline cement slurry is used here too to inhibit corrosion in reo. It works quite well for a time, such as for temporarily exposed bars at joints. .It is quite unnecessary in concrete as the concrete mix contains cement which bonds to the steel. An over-wet slurry may reduce the bond.
 
Hmm, what's the reason for concrete cancer in not very old buildings in Melbourne?
 
I spoke with a concreter who did a garage foundation for us recently and he says that concrete just isn't made like it used to be. It seems more porous than the older stuff. There may even be an element of easier demolition in the 'design'.
 
Nah mate, concrete is very high-tec these days but just like 'oils ain't oils', concrete ain't concrete. A garage footing mix would vary quite a lot in it's chemistry compared to a mix used in something like a pre-stressed bridge beam or similar high load application. Naturally there is a difference in $per m3 between different applications.
 
The Gonz said:
I spoke with a concreter who did a garage foundation for us recently and he says that concrete just isn't made like it used to be. It seems more porous than the older stuff. There may even be an element of easier demolition in the 'design'.
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Small point of correction. The foundation is the earthen material the concrete footing is sitting on.
 
If you had watched the garage slab being laid, you would have noticed-
1. Low strength concrete was ordered to save some money without regard to wear;
2. It arrived with high slump, so has an excess of water which cannot take part in the hydration reactions;
3. The driver and the concretor both added yet more water to make their work easier;
3. It may have been watered more to make pumping easier;
5. Nobody bothered to cure it.

All the above made the slab more porous. That makes the mix design inappropriate. It will likely wear on the surface and may in time have corroded reinforcement. It will certainly be easier to demolish.

The problem isn't the high tech suppliers, as Floride mentioned. It's poor workmanship. Some of the standards of some notorious countries have arrived here. No structural engineer would tolerate much of what goes on at domestic level.

Concrete today, properly specified and laid is far superior to time past. The batch plants carefully measure the aggregates and design mixes to achieve what is required by the order. Years of research have gone into cements, aggregates and mix design.
 
59 Floride (sold) said:
Small point of correction. The foundation is the earthen material the concrete footing is sitting on.
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Nope, 20cm slab for a 16x9m garage. I promise I will never use the term foundation again, but the slab is the foundation for the erection.
 
You would have been corrected in a manner today described as bullying if you had misused foundation when I was at university. Roads have foundations too. In engineering and construction the word has a precise meaning.
 
The Gonz said:
Nope, 20cm slab for a 16x9m garage. I promise I will never use the term foundation again, but the slab is the foundation for the erection.
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And I'm not taking the bait anymore. :LOL: From here on I'm sending out invoices.
 
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seasink said:
If you had watched the garage slab being laid, you would have noticed-
1. Low strength concrete was ordered to save some money without regard to wear;
2. It arrived with high slump, so has an excess of water which cannot take part in the hydration reactions;
3. The driver and the concretor both added yet more water to make their work easier;
3. It may have been watered more to make pumping easier;
5. Nobody bothered to cure it.

All the above made the slab more porous. That makes the mix design inappropriate. It will likely wear on the surface and may in time have corroded reinforcement. It will certainly be easier to demolish.

The problem isn't the high tech suppliers, as Floride mentioned. It's poor workmanship. Some of the standards of some notorious countries have arrived here. No structural engineer would tolerate much of what goes on at domestic level.

Concrete today, properly specified and laid is far superior to time past. The batch plants carefully measure the aggregates and design mixes to achieve what is required by the order. Years of research have gone into cements, aggregates and mix design.
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Hi.

Simples. Just collect some as poured concrete in test cylinders, and make your supply to be contingent on the apprropriate passing of the appropriate test results.

I wonder what the concrete supply company, and the concreter would say if they arrived at site and you had several test cylinders ready and waiting.

I guess that is a little beyond domestic concrete work, but it is the ultimate test.

Cheers.
 
That is what happens when a professional with PI insurance to worry about is visiting. Not only the cylinders, but slump as well. The supply company isn't a problem; they provide as ordered with labs to help, but the dockets can be checked also.

The laying of the said slab needs watching. I haven't mentioned steel. That has its moments too.

You don't know what you have until the cylinder tests come in much later and now things have been built on the work. In days long gone I have had to use a Schmidt hammer for strength reassurance.
 
seasink said:
I have copies of Vitruvius' books, both in Latin and in English with a description of Roman practice. I simplified, but basically, add water to some material from near Naples and you have a cement. I think the simplification is OK for the forum.

Alkaline cement slurry is used here too to inhibit corrosion in reo. It works quite well for a time, such as for temporarily exposed bars at joints. .It is quite unnecessary in concrete as the concrete mix contains cement which bonds to the steel. An over-wet slurry may reduce the bond.
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The Roman concrete made with Tuff ( volcanic rock crushed finely ) would also set underwater, so good for piers etc. And was bloody tough and long lasting, a good example being the Pantheon in Rome

a
 
The Pantheon (it was perhaps named that for a while at first, it's been a church much longer) used the volcanic ash deposit at Pozzuoli, which is a silica and aluminium compound, like modern kiln-fired Portland cement, with, in the case of Roman cement, an admixture of calcium hydroxide (quicklime). The calcium carbonate formed has given the material its ability to self heal tiny cracks.

The Roman building was also an unreinforced dome, on a massive butressed base, so if water did get in no steel would oxidise and expand.

We can do much tougher concrete today. Unreinforced material has limited uses that are not stressed in tension.

Fly ash, silicon-aluminium residue from power station coal burning, is also now a common cement.
 
... and, apparently, concrete is the new place to 'recycle' (hide?) chopped up old wind turbine blades.
 
It's a hell of a big lump of fibreglass to put in the recycle bin. Might as well use it in something that is already fibre reinforced.
 
David S said:
... and, apparently, concrete is the new place to 'recycle' (hide?) chopped up old wind turbine blades.
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They shred them for aggragate, and they also "recycle" them by grinding them up and incierating them to make clinker, also for the cement.
When I was telling a mate of mine they recycle wind turbine blades by burning them, he said:
"what are they recycling them into, cancer"?🤣
 
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