curvilinear control joints in concrete slab

[ieranger]

We are designing a decorative concrete plaza with colored concrete. The landscape designer wants to have a wavy pattern cut in to the concrete. Can curvilinear control joints be used to control the crack locations in a concrete slab or does concrete just want to crack in straight lines, and the the cracks would not stay in the waves? Will control joints with a large radius work and is there a minimum suggested radius for a curved control joint?

 

[MotorCity]

Control joints are purely for aesthetics. Its like telling the concrete that you want nice straight cracks in a particular location. Without the control joints, you will most likely have random crack patterns in random locations.

So yes, theoretically curved control joints will serve the same function as straight control joints as long as they are not spaced too far apart. You would have to talk to a concrete cutting contractor for recommendations on the minimum radius, but from what I have seen the walk behind concrete saws cannot turn very sharp.

 

[KootK]

It makes me nervous but there has to be some radius over which cracks would be willing to chase the waves rather than cut across. I took the photo below at the Pat Tillman bridge last weekend specifically because of how well coordinated the jointing was between the SOG, walls, and handrails. It's got a tight radius and a tight joint spacing.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[KootK]

Now that I think of it, maybe those are construction joints. And that might be a strategy for you. It would drive up cost of course.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[dcarr82775]

Koot,

You need to get into therapy man. Vacation, try to turn of the brain for a couple days.

 

[KootK]

Hey! I gambled pathetically, watched a very uncomfortable Zumanity show, ate shamefully, and even raced a Ferrari five laps in the desert. I did Vegas up right. The pic was from Hoover Dam day. You couldn't expect me to tuck it away for that could you?

I actually held back here. I've got some great pics of a giant Ferris wheel built exactly like a bicycle wheel that I'm dying to discuss. It couldn't be helped. It was right out front of my hotel.



I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Ron]

Here's the problem with curvilinear joints....

Concrete shrinks volumetrically. As a result you get very little shrinkage in its thickness, but greater shrinkage in its length and width.
It shrinks in a relatively uniform manner, assuming the thickness is well controlled. When you have curvilinear patterns in the control joint, the opportunity
for the parts of the joints that are curving closer together to have a random crack connect them. "Soft, large radius curves are probably OK. If you
have closely spaced curves, there's a good opportunity for those to connect with a crack across the joints.

 

[cvg]

tool your curvilinear pattern, then sawcut the slab at the typical spacing. the sawcuts will handle the shrinkage, the tooled joints will look pretty.