Saw cutting contraction joints in sidewalk


  #1  
Old 08-21-11, 07:39 PM
K
Member
Thread Starter
Join Date: Aug 2011
Location: USA
Posts: 2
Likes: 0
Received 0 Likes on 0 Posts
Saw cutting contraction joints in sidewalk

I poured my sidewalk yesterday. When is the best and safest (to prevent chipping) time to sawcut my contractionjoinnst and what is teh recommedned depthof teh cut? I assumed after I remove the forms 3 days from yesterday, but was not sure. Thanks
 
  #2  
Old 08-21-11, 08:37 PM
Join Date: Mar 2005
Location: USA
Posts: 6,130
Received 0 Likes on 0 Posts
Cut as soon as you can walk on the finished slab without damage (8 to 24 hours) with a soft cut blade. Waiting can cause problems and cracks.

The suggested depth is about 1/4 to 1/3 of the thickness.

Dick
 
  #3  
Old 08-21-11, 08:39 PM
K
Member
Thread Starter
Join Date: Aug 2011
Location: USA
Posts: 2
Likes: 0
Received 0 Likes on 0 Posts
What is a soft cut blade?
 
  #4  
Old 08-21-11, 09:17 PM
Join Date: Mar 2005
Location: USA
Posts: 6,130
Received 0 Likes on 0 Posts
That is a specialized blade for cutting "green concrete".

In your case, cut as soon as possible because there could also be some unseen shrinkage cracks by now, but future cracks can be minimized with a quick saw cut. Any concrete that is poured wet or sloppy will be more likely to crack.

The forms could have been removed the day following the pour.

Dick
 
  #5  
Old 08-22-11, 03:32 AM
P
Member
Join Date: Feb 2005
Location: USA
Posts: 1,396
Likes: 0
Received 0 Likes on 0 Posts
As Dick said, cut as soon as possible. Cut the walk into squares. That is, if it's a 4 foot wide walk, cut them every 4 feet. Too wide a span between joints will also lead to random cracking.
The best tool to use is a gas powered concrete saw equipped with a diamond tipped blade. It will saw like butter. If you use an electric saw with a fiber/carborundum blade, you'll be there for hours. Wear a dust mask and eye protection!
 
  #6  
Old 08-22-11, 06:26 AM
M
Forum Topic Moderator
Join Date: Mar 2005
Location: USA - N.E.Tn
Posts: 49,330
Received 698 Likes on 616 Posts
I'd second the renting of a gas saw! I've seen some use a 2x to help them cut a straight line. While I've never saw cut any concrete I've been on a lot of jobs where it was being done. I wouldn't want the amount of concrete dust that is generated clogging up my skil saw
 
  #7  
Old 08-23-11, 04:16 AM
P
Member
Join Date: Feb 2005
Location: USA
Posts: 1,396
Likes: 0
Received 0 Likes on 0 Posts
It's not just the dust or the wear on your circular saw, it's the time, materials, and joint effectiveness involved.
You'd go through a few fiber blades, and they would keep wearing down so the later joints would end up being too shallow to be effective. Also, since electric saws spin backwards, they're more likely to kick back. Gas powered saws pull the blade along instead of pushing it back at you.
 
  #8  
Old 08-23-11, 07:24 PM
XSleeper's Avatar
Group Moderator
Join Date: Dec 2004
Location: USA
Posts: 29,418
Received 1,571 Likes on 1,409 Posts
I've had problems result from cutting TOO deep on sidewalks with no reinforcement (slabs cracking clean through and heaving or settling). So I'd lean towards a maximum cut of 1/4 depth.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: