Dramix 4D Fibers - Saw Cut Control Joint Issues 4

[larsacious]

We are using Dramix 4D fibers on a project and the contractor is having difficulty saw cutting the control joints. The specification is to saw cut within 4 hours. If they cut that early the saw blade catches the fibers and it makes a mess out of the joint. Our curing conditions are generally favorable with temperatures in the 60's to 70's. After the last pour they had to wait 15 HOURS after the initial set before they could cut. We are experiencing some microcracks around re-entrant corners but for the most part the slab is holding together likely as a result of re-entrant reinforcing bars.

We have worked with the fiber supplier but they are not able to provide any further recommendations other than wait until the fibers don't rip out.

Just wanted to find out if anyone else has experienced something similar to this.

P.S. Contractor is using brand new diamond tip saw blades and a relatively new Huqsvarna saw.

 

[Enable]

Are you positive that it is the fibers being caught? They are so thin that a new diamond blade should cut right through them almost instantly.

You mentioned that your contractor is using a Husqvarna saw but did not mention what type. Do you know if it's a soft-cut saw? You can't use a regular saw to cut fresh concrete and the pitting makes me think they are using the incorrect saw type. That's the first thing I would confirm. After that, I really see no option other than to wait it out and keep a good wet cure on the surface. If you have a proper saturated wet cure cutting the next day should still mitigate most of the visible cracking.

 

[JLNJ]

These are steel fibers. Depending on the dose the saw has some work to do.

If you have to wait 15 hours, maybe you don't need the joints, or at least a heck of a lot fewer of them.

 

[dik]

If you wait 15 hours, you may as well use the cracks as a sawcut guide... the soff-cut saw is a great invention...

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

-Dik

 

[GC_Hopi]

They recommend 16 to 24 hours before saw cutting on the website. Like the OP said its a different animal. Last video on the page Link

 

[dik]

Who is they? Dramix? Too long IMHO...

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

-Dik

 

[GC_Hopi]

The manufacturer, Bekaert, is recommending that. I don't have any personal experience with steel fiber so I found that interesting. It seems like saw cutting is more art that science. Contractor has to be experienced to know when the concrete is just right.

 

[Tomfh]

That sounds really difficult cutting a fibre reinforced slab that hasn’t gone off yet.

 

[Ron]

Use a soff-cut saw, not a conventional saw. The blade is thinner and the saw is higher speed so ravelling is usually not an issue, even with steel fiber. If you're sawcutting in 4 hours with conventional equipment you are getting exactly what I would expect.

Check your mix design...if it contains fly ash or GGBFS, strength gain is slower so you can delay sawing a bit, but not beyond 8 hours in any case.

 

[dik]

my understanding, too... thanks Ron

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

-Dik

 

[larsacious]

Thank you everyone for your input. They are using a 4,000 rpm soft cut saw. We are going to look into the 6,000 rpm saw that was suggested. Unfortunately, their 16 to 24 hours before cutting is not practical in an exterior slab pour in the upper, midwest in spring time when temperatures drop into the 40's overnight.