Concrete Strength News 1

[dik]

from Construction Canada:

https://www.constructioncanada.net/...=email&utm_source=newsletter&utm_content=news

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[STrctPono]

I'm going to play the devil's advocate here for a minute.....

Using externally applied sound waves to test concrete's densities and thus corresponding strengths is nothing new as they have been doing this with ultrasonic testing. Doing it real time using embedded sensors seems to be new. But this begs the question, what does this really solve? Is this that much cheaper than casting concrete cylinders? What benefits does having real time strength data provide that a 3, 7, 14, or 28 day strength can't tell you. I only work in 1 industry so perhaps there are many benefits that I am just not thinking of.

When we require contractors to embed sensors and generate a maturity curve it's typically tied directly to a thermal control plan.

 

[r13]

Agree with the cost-effectiveness argument. But thinking in terms like "smart building", maybe the research has merit.

 

[dik]

done that lots of times with mass concrete... very common... I thought the article was a neat idea... and Construction Canada is one of the best 'trade' journals... My concern is that I personally like to see concrete test results above that spec'd... and not sure how I'd react to concrete always being 'at the min spec'.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[r13]

Construction Canada is one of the best 'trade' journals... and Prudue U is a prestige engineering school in the US. If I didn't mess up the source

 

[dauwerda]

What benefits does having real time strength data provide that a 3, 7, 14, or 28 day strength can't tell you.

Say you haven't hit the strength you need to continue construction with the 3 day break. Now you are stuck waiting until day 7. Or, with real time, you now see on day 4 that you hit the strength you need and can start the next sequence of construction 3 days earlier than you would have otherwise.

 

[STrctPono]

Say you haven't hit the strength you need to continue construction with the 3 day break. Now you are stuck waiting until day 7. Or, with real time, you now see on day 4 that you hit the strength you need and can start the next sequence of construction 3 days earlier than you would have otherwise.

I guess this is really important when you're constructing a structure that will be occupied by some business that generates money so there is an incentive to finish construction early. Not sure if I've worked on 1 single construction project my whole career that has ever been completed early!

 

[r13]

In my experience, most of the early completions are tied to the hefty incentive the owner provided. Not unusual in certain industry, for which time is money, or even more precious than money.

Timely finish is expected for private construction due to "late fee/fine" clause in a well written contract. However, huge delay seems to be the norm for government founded projects, due to founding issues and corruptions behind, or just greets in general.

 

[structuralCADspecialist]

I got half-way through the article and stopped reading. Not because this is a bad idea or a bad article (and as someone pointed out, it's not a new idea). They mention that it takes one month to test the 'concrete mix design' - in reality it probably takes longer. Technically years if you consider factors like freeze/thaw, durability, etc... Luckily, people have already tested this (and are continuing to test this). ACI has done a pretty good job of this. So to the point: Rarely is something built from a brand new, untested concrete mix design. For most commercial projects, simply specifying performance requirements (the average engineer shouldn't be specifying the mix design unless it's a special case) is sufficient and the supplier will provide a mix design that meets or exceeds (usually exceeds) that requirement. And that mix design will not only have a proven record of performance, but also an abundance of statistical data helping cover their butts should they have a 'bad' batch of concrete.

Also, concrete strength isn't the only factor affecting when you'd strip. For slabs, you'll get excess creep if you strip early. Not to mention construction loads (I wish every engineering who designs concrete slabs could see every step in their construction). For any projects I have a say in, they won't be stripped until the cylinder tests say they can be stripped - and that's at the absolute soonest.

 

[BridgeSmith]

...Prudue U is a prestige engineering school in the US. If I didn't mess up the source

Only the spelling...

Rod Smith, P.E., The artist formerly known as HotRod10

 

[r13]

Rod,

Good catch. Thanks.

 

[dik]

The publication has extremely well written articles, and really technical in most instances, about construction... been receiving them for decades... only change is they've gotten a little thinner. It's my favourite, and as an info junkie... I should know.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

I see these less and less... with case law, many courts insist that if there is a penalty clause, then there should be an equivalent bonus clause... a bonus clause of $1 vs. a penalty clause of $100, won't fly... also, if you're a sharp creative contractor you can find many 'real' excuses for a delay, and the owner will be put on notice for each and every one. After getting real 'hurt' on a project in Saskatchewan a couple of decades back... I started using Extra Service Work Orders 'ESWOs' to identify changes to the project and hours delayed and added fee...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik