Cast with mortar in September now a pile of sand, why?

[Tyresö]

Exactly, but what about those who should know better, those who mixed the concrete for the Öland Bridge. Apparently, they took water from Kalmarsund, = brackish water, so the damage didn't wait long to appear.

Hahaha, they are now sitting and giving expert advice here on the forum......

There are a number of constructions here in Stockholm as well that are completely ruined because they took water from the Salt Sea when they mixed concrete in the 70s. All the reinforcement is rusted and the concrete is crumbling.

 

[Tyresö]

Of course, Töutansalt is an option, I should check this and force it on mom because concrete or something like that must be used since the stairs are not attached to the house wall with anything else but this.

I have no knowledge of "Tö utan salt" but I don't trust such chemicals when we have our own drilled well. Also, I don't trust that the concrete construction will remain completely undamaged. It's possible that I'm overly suspicious, but what's wrong with regular gravel?

 

[Gustavsson]

Not at all, and I will get her to use it, but the thing is that she lives quite a distance from me, so I can't always come and shovel for her in the winter, even though we don't often get much snow down here. So the times I can't get to her, she pours out a bit of salt instead, and it's gone or much less a day later, but gravel doesn't have that property.

I checked thawing salt, and the contents were nothing I see that can directly affect, for example, concrete, but I don't know what it costs. So as long as there is packed snow or ice, it's gravel she will have to use from now so that something can be cast there properly.

 

[Stringfellow Hawke]

Now I think you're being a bit too aggressive Tyresö!

Exposure class XD3 handles salt very well, e.g. de-icing salt. At least for a heck of a lot of years. How else could we make parking garages?

Then it's also true that the concrete itself isn't seriously damaged, but the pH is lowered and then we get rusting reinforcement.

 

[Tyresö]

Now I think you're being a bit aggressive Tyresö!

Exposure class XD3 can very well handle salt, e.g., de-icing salt, at least for many years. How else could we build parking garages?

Then again, the concrete itself isn't seriously damaged, but the pH drops, and then we get rusting reinforcement.

Yes, that's the exposure class I have for our concrete structures at home, and you're quite right when you claim that this concrete withstands salt. By "quite," I mean that even that quality of concrete is affected by salt - the only difference is that it takes longer.

Speaking of parking garages... if you only knew how many thousands of m2 of parking decks I've pumped concrete into when customers have done overlays (5 cm) because the concrete surface is completely corroded by salt - and that's just from the salt brought in by passenger cars. Every 15 years, the concrete surface must be repaired with an overlay because of the salt.

If they had used exposure class: XO - which is the most common class a DIY enthusiast (unknowingly) usually mixes for personal concrete staircases, etc. - then the parking decks would need repair every other year.

 

[jhenrikj]

Now I think you're being a bit too aggressive, Tyresö!

Exposure class XD3 handles salt very well, e.g., de-icing salt. At least for a heck of a lot of years. How else could we build parking garages?

Then it's also the case that the concrete itself isn't seriously damaged; however, the pH is lowered, and then we get rusting reinforcement.

In a parking garage, horizontal surfaces are usually covered with waterproofing layers and asphalt. The concrete is therefore not exposed to large amounts of salt that remain on the surface. Beams and columns are exposed to salt spray, but most of it runs off. That's why we can build parking garages.

 

[Gustavsson]

Is concrete with an exposure class XD3 or similar something that can be obtained in stores? If it would last at most barely 10 years or so, it would have been completely fine as she didn't plan to live there that long anyway.

 

[Tyresö]

Is concrete with exposure class XD3 something that can be found in stores? If it lasted at most just under 10 years or so, it would be perfectly fine since she hadn't planned to live there that long anyway.

No, a private individual does not have access to air-entraining agents or superplasticizers for a mix ratio to achieve an optimal WCR value in the concrete (lower than 0.40).

Instead, try to buy regular fine grade concrete and add 0.5 - 1 L of standard cement/fine grade concrete bag. Then you'll have a decent concrete quality.

 

[Stringfellow Hawke]

In a parking garage, horizontal surfaces are normally covered with waterproof layers and asphalt. The concrete is not exposed to large amounts of salt that remain on the surface. Beams and pillars are exposed to salt spray, but most of it runs off. That's why we can build parking garages.

I've never done it that way, anyway... I'm probably talking more about parking garages under multi-family buildings, usually driving directly on the ground slab.

Tyresö: Yes, I know, but honestly, how long have we had the concrete quality that we have today? (The same quality in all cars, low-wct concrete, good flow additives, etc.) 15-20 years?

 

[Tyresö]

Well, I've never done that anyway... I'm talking more about underground parking garages in apartment buildings, perhaps, usually you drive directly on the ground slab.

Tyresö: Yes, I know, but hand on heart, how long have we had the concrete quality we have today? (Same quality in all cars, low-wct-concrete, good flow additives, etc.) 15-20 years?

Low WCT value has always existed through mixing in enormous amounts of cement. The flow agent just allows you to maintain a low WCT value while still achieving a fluid consistency, and the flow agent has been around for about 25 - 30 years.

On the other hand, the air-entraining agent has been around for more than 30 years, but the most important thing for making concrete more resistant to salt is still a low WCT value. The air-entraining agent is more helpful for surface freeze-thaw resistance on concrete surfaces and doesn't have much to do with salt resistance.

 

[Gustavsson]

No, an individual does not have access to air-entraining agents or superplasticizers for a mix ratio to achieve an optimal WCR value in the concrete (less than 0.40).

Instead, try buying regular fine concrete and add 0.5 - 1 L of standard cement/fine concrete bag. Then you have a decent concrete quality.

Aha, so there are so many things in it, that's too bad but the mixture you mentioned I will definitely try, thank you for that!

 

[jhenrikj]

Then it's not just the quality of the concrete that determines how long it lasts. If you're dealing with XD3, substantial coverage layers on the reinforcement are required. With a w/c ratio of 0.40, the base measure for the covering concrete layer is 45mm for L50.

So...w/c ratio is the water-cement ratio, meaning the ratio between the amount of water and the amount of cement. It's not a problem for anyone to mix a concrete with a 0.40 w/c ratio. The issue is that the concrete you get will be very difficult to work with and sets incredibly quickly ;=) If, like Tyresö, you're going to drive such concrete around in a concrete truck, it takes a heck of a lot of additives for it to be usable by the time you get to the customer. If you're mixing at home in a mixer, it's theoretically possible to manage without additives, but the precision of the mix becomes too poor, so in practice, it probably doesn't work so well...

 

[Tyresö]

Then it's not just the quality of the concrete that determines how long it lasts. If you're dealing with XD3, substantial cover layers on the reinforcement are also required. With wcr 0.40, the base measurement for the covering concrete layer is 45mm for L50.

In other words... wcr is the water-cement ratio, which is the ratio between the amount of water and the amount of cement. So, there's no problem for anyone to mix a concrete with wcr 0.40. The problem is that the resulting concrete becomes very difficult to work with and sets extremely quickly. ;=) If, like Tyresö, you drive this kind of concrete around in a cement truck, a whole lot of additives are required to make it usable when you get to the customer. If you're mixing at home in a concrete mixer, it's theoretically possible to manage without additives, but the precision of the mix becomes much too poor, so in practice, it probably doesn't work that well....

Exactly - how is a do-it-yourselfer supposed to know the mix ratios - water - cement - sand/crush to achieve such a low WCR value?

Moreover, if you have stronger concrete, you have to compensate with stronger/denser reinforcement.

Even if, as a private customer, you were to have access to - retarder - air-entraining agents - superplasticizers, how is a do-it-yourselfer supposed to know how to dose these additives? They are so extremely concentrated that just an extra 2 cl of something in the mixer, and the concrete turns into a disaster.

It's possibly okay to overdose the retarder, but too much superplasticizer separates the concrete = pour out the mixture and start over. Too much air-entraining agent makes the concrete too brittle when cured, leading to significantly reduced strength.

So the only real thing to do as a do-it-yourselfer, if you're going to cast a horizontal outdoor construction - call a concrete station and have properly lab-tested concrete delivered - even if you only need 0.5 m3.

Homemade concrete is only suitable for indoor constructions or concrete columns for terrace projects.

 

[Alfredo]

Exactly - how is a DIY enthusiast supposed to know the mixing ratios - water - cement - sand/crushed to achieve such a low WCR value?

The answer is obvious - he should ask Tyresö at byggahus.se d^_^b Then he'll probably still not succeed, but that's another matter!

 

[Gustavsson]

The problem now is that only about 2 - 3 liters of concrete are needed for this, and I don't think they would deliver that amount, so I don't have much choice but to mix it myself with the stuff that I, as a private person, can get hold of, and then it will be what it will be, right? It's not completely horizontal but at a 45-degree angle, and if it lasts 5, 6, 7 years, that's perfectly fine with me.