Expansion Joints

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Expansion Joints

Postby pklongball » Mon Sep 02, 2013 9:27 am

Hey all you concrete experts. I have looked through this topic for any info about concrete expansion joints and what I found so far is not exactly what I wanted.

First of all the terms in Thai. Does someone have a known translation for the terms "concrete expansion joint"? Here is what Google says and my wife says it looks pretty good

ร่วมขยายคอนกรีต
"concrete expansion joint"

Anyone can add something?

Also where can you buy the joint material such as foam or pvc or fiberboard or what?

In a 7 meter by 7 meter slab how many joints would be good to have? Just an even division with a joint top to bottom and also side to side?

I can google all sorts of help but these searches produce results in places where explaining this need to a contractor is almost not needed as they would automatically install the joints. Convincing a Thai to do it "your" way instead of "his" way is another thing. Something with pictures would be great especially if it's what you did here on your build project.

Thanks for the help as I know there are many concrete experts here.
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Re: Expansion Joints

Postby MGV12 » Mon Sep 02, 2013 11:03 am

Come on PK ... you really should know better :roll:

What is this 7X7 slab going to be used for? Drying the washing? Building a shop house? Parking a Panzer VIII?

What is underneath the slab? Rock? Compacted sub-soil? Dirt?

The slab itself ... CPAC [type] ready-mix - if so what Steng? DIY mix?

My neighbour has a driveway that's 15 metre by 15 metre [L-shaped] it's no more than five [max seven] cm's thick ... over ballast that was simply rolled into the dirt by driving a pickup over it. Two years later I can't see a crack.

Most 'contractors' ... if the end user insists ... pour the slab and then scrape a groove into which they insert strips of the one inch thick polystyrene sheets you can buy at any artists materials shop. This general approach is used universally as it provides a fault line through which any stress's between the slab and the substrate can dissipate ... you dictate where the crack will occur. In practice the Thai approach unfortunately does not usually meet Farang aesthetic standards. What is the need or purpose of a straight line after all? :roll:

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Re: Expansion Joints

Postby pklongball » Mon Sep 02, 2013 12:54 pm

Ok so sorry but I wrote the topic while waking this AM and drinking coffee. My mind was focused on the translation side of the question.

I am constructing my carpark now and the driveway leading to the structure needs concrete. So the immediate area in front of the carpark is about 7x7 that currently is gravel that has been there for over 4 years now. The goal is to make the entire drive in and approach to the carpark 12 cm thick concrete and I will start with a 7x7 area i ask about. The current gravel was compacted 4 years ago and is about 6 inches thick. At least 4 inches of this gravel will be removed to make the concrete slab/drive. No plan to tile this area. So trowelled concrete fairly smooth with some joints added would be good enough.

Hope this helps you show me a translation for expansion joints.

Thanks
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Re: Expansion Joints

Postby MGV12 » Mon Sep 02, 2013 2:50 pm

pklongball wrote:
Hope this helps you show me a translation for expansion joints.

Thanks


As you went into some detail and put your question in the concrete thread thought you wanted advice on the expansion joints as well as a Thai name

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Re: Expansion Joints

Postby canopy » Tue Sep 03, 2013 7:15 am

Even in English there are different terms for them. I think from most correct to least is: control joint, contraction joint, expansion joint. Concrete shrinks as it dries and the control joints will define where cracking occurs *if* the ground is properly compacted, the concrete is properly mixed, properly vibrated, and properly cured. It's a lot more neat and tidy to have an invisible crack under a straight joint than a spider web of cracks on the surface which could chip off especially as you will have vehicles running over it. My experience for residential purposes is Thai builders don't know about any concrete joints nor understand why you would need them. Concrete jobs in Thailand tend to crack badly due to compound errors and it's considered a "normal" attribute of concrete to them and so they don't care. I am appalled even new, giant building stores that have concrete floors inside are full of big ugly cracks and have parking lots that puddle water. What a shame. So if you want to explain to a Thai what they are, they may not even know the name. Just go to any concrete road and point at it. Concrete roads at least in my parts always have control joints at short intervals.

Every specification I have seen would indicate a 7x7M area requires control joints. You could look up a design on the web and it would be better to post your questions on a concrete forum with experts. One method to make them is to use a concrete groover while the concrete is wet, but my recommendation is to run a circular saw with a diamond blade after it sets a bit. Among other advantages it allows you to set just the right depth and moves this important activity away from being a distraction getting the time critical slab poured right. Also install isolation joints anywhere the concrete meets any posts. And if the plan is to extend the slab later don't forget to join the slabs with a construction joint. These are all just the normal way of doing things that Thai's have yet to learn to the determent of the owner.
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Re: Expansion Joints

Postby pklongball » Tue Sep 03, 2013 8:19 am

Thanks Canopy for the words of wisdom.

I put the question/topic in the concrete forum as the question is concrete related and IMHO was most likely to get a response there as it pertains to concrete and mortar work.
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Re: Expansion Joints

Postby BKKBILL » Tue Sep 03, 2013 10:03 am

PK, can't wait to see the pictures :mrgreen: .
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Re: Expansion Joints

Postby Mike Judd » Thu Sep 05, 2013 12:02 pm

Having a bit of a break from my dramas with septic tank and catching up with the Forum ,I couldn't resist commenting . All concrete paths ,slabs etc should have expansion joints , whether foam against any walls and in their lengths every 6mt max. Cutting a grove later in driveways or even paths later is O.K as a means of controlling where it will crack, as it will surely do. Just have a look in the next Petrol station area to see all the cracked concrete if they havent bothered.
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Re: Expansion Joints

Postby ajarnudon » Sat Mar 25, 2017 6:25 pm

Indeed, they are control joints (not expansion joints), allowing you to choose a straight line for the inevitable crack to follow. Inevitable, because as stated above, concrete shrinks as it cures. Six metres would be an absolute maximum spacing. The most important use of foam strips is between horizontal concrete surfaces such as driveways and walkways, and the walls of your home. An incredible amount of heat is stored in the horizontal concrete slab from the sun beating down on it, and the foam prevents thermal transfer to the walls of the house.
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Re: Expansion Joints

Postby Roger Ramjet » Sat Mar 25, 2017 7:07 pm

ajarnudon wrote:Indeed, they are control joints (not expansion joints), allowing you to choose a straight line for the inevitable crack to follow. Inevitable, because as stated above, concrete shrinks as it cures. Six metres would be an absolute maximum spacing. The most important use of foam strips is between horizontal concrete surfaces such as driveways and walkways, and the walls of your home. An incredible amount of heat is stored in the horizontal concrete slab from the sun beating down on it, and the foam prevents thermal transfer to the walls of the house.


The member you are talking to, Mike Judd, passed away last year. The Thai doctor claimed it was old age but his wife informed me that it was actually an asthma attack prior to and during his visit to the Thai hospital.
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Re: Expansion Joints

Postby ajarnudon » Sat Mar 25, 2017 10:27 pm

Thank you RR. My condolonces to his family. Nevertheless, I left my post for others who might later look at this topic - particularly regarding insulation from thermal transfer from horizontal slabs to vertical house walls.
I really appreciate your putting me straight.
Regards, John
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