Filling in cut expansion joint in concrete

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Old 07-15-08, 12:54 PM
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Filling in cut expansion joint in concrete

Hello,

I recently had about 6 slabs of my concrete replaced, because the old ones were cracked. I live in Michigan. The day after the concrete was done, they came back, and cut expansion joints. They were cut 1 inch deep, and are about 1/8 inch wide. Should I fill this with some backer rod, cauke, something else? Thanks, Doug
 
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Old 07-15-08, 04:57 PM
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I would leave it for 2 reasons. You don't want to inhibit the expansion and just in case the pitch isn't right and the water has no place to go.
 
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Old 07-15-08, 06:43 PM
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Filling in cut expansion joint in concrete

I assume this is a driveway if you had 6 slabd removed.

You do not have an "expansion joint". You have a control joint to control where the concrete cracks. You should have a crack through the slab in a week or so, but will never see it. All concrete cracks over time, with most happening in the first few weeks.

Leaving it open invites many problems.

First, if it is open you will get more water under your slab.

Second, dirt and salt can accumulate in the joint, attracting more moisture that will freeze and expand, possibly damaging the slab. Michigan is notorious for high useage of salt.

Third, the excess moisture in the soil, wekens it and can lead to deflection and cracking. Have you ever wondered why so much time and money is spent filling joints on roads. - It is to prolong the life of the road surface and base material.

A properly installed slab will shed water to the sides and does not need artifical drains in the middle.

Use a high quality caulk and force a bead into the joint, so that you have good attachment to both sides of the joint. If the joint is too wide, use a backer rod inserted deep enough to get the bead to spread and adhere.
 
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Old 07-16-08, 11:45 AM
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concrete control joint

OK, I guess this isn't black or white, since I have 2 differing opinions on what to do.

Concretemasonry: You mentioned to use backer rod, if the joint is too wide. The joint is 1/8 wide, and 1 inch deep. So do you recommend using backer rod?

If not, how would I get cauke to seep all the way down to the bottom of the 1 inch deep joint?

thanks, Doug
 
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Old 07-16-08, 11:58 AM
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Doug
It doesn't have to get to the bottom, just seal the top from water penetration and debris. What CM was saying was that you want to force a wide enuf bead in so that it adheres well to both sides of the cut, not just on the top 1/8". Use a good pro quality caulk designed for concrete.
 
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Old 07-20-10, 03:52 PM
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Expansion joints

I've found that Dow Corning has a good pavement sealant for expansion joints. It's good for handling weather extremes and any movements that may occur with expansion joints.
Dow Corning Pavement Sealants for highways, bridges and runways - Dow Corning
 
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Old 07-20-10, 04:59 PM
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Water in cement cracks is a bad thing if it freezes where you live. I used some stuff from the big box last year. It's in a tube like regular caulk. I found it in the cement aisle not in the caulking aisle. Easy to use and it held up over the winter.
 
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Old 07-21-10, 02:34 AM
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I concur with the guys who said to fill it with caulk. You don't necessarily HAVE to do it, but it could help and certainly can't hurt.
 
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Old 07-21-10, 02:23 PM
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Dick, and others, I have used butyl rubber in caulk form to put in control joints and it holds up pretty well. It expands and contracts and isn't affected too much by weather extremes. Not sure of your take on that. Just thought I'd throw it out.
 
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Old 07-21-10, 02:51 PM
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Well...it is a 2 y/o post...so now its just a general info thing...
 
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Old 08-01-10, 12:47 PM
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things must be slow if we're bumping up old posts.

ps - dick's still right
 
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