Recommendations for filling concrete driveway expansion joints

[Capt W]

I'm looking for a decent pourable filler for my expansion joints. The joints were originally filled with 1x2s, but those are 21 years old and are rotting away to nothing. Water intrusion has created a few voids below the slabs, so I want to seal it all up. I'll probably have to replace the whole driveway in five years or so, but at present just want to fill the gaps for aesthetics and add a bit of longevity.

I plan to pull all the remaining 1x2s, fill any voids under the slabs with foam, and re-install new 1x2s. I'd like to top it all off with some self-leveling sealant to keep most of the water out and provide a neater look. FWIW, the joints are about an inch wide by two inches deep. Adding the 1x2s will naturally fill most of the space; the filler will simply seal it up.

Problem is I can't seem to find the right product in a decent quantity/size. Last year I performed a similar repair to a small section near my garage. I used Quickrete concrete filler, which despite a few cracks turned out OK. Problem is the small section took almost an entire quart, and squeezing the material out of the small bottle took way too long. And filling with standard caulk gun-sized cartridges would also take hours and hours. Anybody have a favorite product for this purpose? Specifically looking for something that comes in a gallon size and can be easily/quickly squeezed out.

First pic is the area I repaired last year. It has a new 1x2 below the sealant.

 

[Pablo]

Replace wood

Or concrete grout over backing foam rods

 

[Lubener]

If you can use something ( backer rod, sand, new wood etc) to fill the void where there are no gaps up to about 3/8 inch from the top, I would use a self leveling urothane. If you are close to 3/8 inch, you don't need anything. It's just to save on the urothane.

 

[Pablo]

If you can use something ( backer rod, sand, new wood etc) to fill the void where there are no gaps up to about 3/8 inch from the top, I would use a self leveling urothane. If you are close to 3/8 inch, you don't need anything. It's just to save on the urothane.

Need UV resistant coating or urethane itself. If not will get ugly in the sun

 

[JohnnyG]

Do you remember Thiokol?

Not sure if they are still in business, but they made a great flexible polymer crack filler. Best stuff ever for non critical missions. I think it might shrink a bit in extreme cold though.

 

[pbm]

Did they use pressure treated 1x2s? I did 22 years ago and they are still good. I agree on the urethane.

 

[f355spider]

I've used a special concrete caulking compound sold at concrete specialty manufacturer only a couple miles from me. I forgot what it cost, it was several years ago...I went through several tubes. It came in a few different colors...I got the standard grey. I'm sure there are similar products at contractor supply or hardware stores.

 

[clinebarger]

NP1 polyurethane sealant

 

[ecotourist]

I've had 2 contractors at my place recently. The recommendation is to loosen any remaining rotten wood with a circular saw (using eye protection and a safe depth of course) and then fill the now clean joints with sanded grout (which is available in various colours).

 

[Carmudgeon]

I've used the Sikaflex product, and it only lasts a few years before hardening and cracking. Cost adds up as well, with the regular sized tubes that fit in a standard caulking gun. They do have larger tubes, but those need a different gun.

My preference would be the felt strips, but for whatever reason, it's difficult to find at the consumer level, and very costly otherwise.

 

[Capt W]

Thank you for all the inputs! After some deliberation I'm going to use weather-treated 1x2s and fill with Sikaflex poly sealer. It comes in a larger 29 oz. tube like Carmudgeon stated, so I'll have to buy one of the large caulk guns. The reviews on Home Depot are overwhelmingly positive, with lots of folks using the stuff for expansion joints. Should only need 4-5 tubes, so this is probably the best solution for me. I appreciate your advice...it's exactly why I ask questions on this forum!

 

[50yr Street Mech]

Had a concrete driveway at my 1st house. The contractor put felt in, but that fell apart with all the salt used here in the Salt Belt. Used the 29oz tube of Sikaflex with the larger gun. Poured it right over the felt, and it worked fine. Stuff was not cheap, but was worth it. After a few years, it would get a bit moldy, but a powerwasher cleaned it right up. Now I have an asphalt driveway in the new house, and all I do is chase cracks to seal them up. Can't win

 

[doitmyself]

Everything I've studied states the correct way is to use backer rod and sealant to achieve an hourglass shape:
https://www.emseal.com/article/hour-glass-tension-backer-rod-caulk-sealant/

There's this stuff also (no experience with): https://www.trim-a-slab.com/how-it-works/

 

[zzyzzx]

I use spray foam as a backer then one of those self leveling products that remains flexible on top of that. When I apply the self leveling stuff I put something at both ends to make sure that it doesn't run out. This works way better than the stuff that's basically gray caulk (which usually just separates over time). My method isn't cheap or easy (multiple steps) but it does last.

 

[Capt W]

I thought about your method since I'm using spray foam to fill various voids underneath the slabs. How do you control the foam as a backer when the stuff expands faster than JB Prtizker at a buffet? Seems like trimming it all back would be a real pain...

 

[Pablo]

I thought about your method since I'm using spray foam to fill various voids underneath the slabs. How do you control the foam as a backer when the stuff expands faster than JB Prtizker at a buffet? Seems like trimming it all back would be a real pain...

Use the low expansion stuff

I jammed a French door closed with the expanding stuff so don’t ask me how I know

 

[JTK]

Do any of the concrete sections move with your climate and usage? Where I live, freeze/thaw cycles would crack any solid filler put in those gaps.

 

[BMWTurboDzl]

Replace wood

Or concrete grout over backing foam rods

I used a flex sealant over foam rod.

 

[Capt W]

Do any of the concrete sections move with your climate and usage? Where I live, freeze/thaw cycles would crack any solid filler put in those gaps.

For sure...that's why I want something of a flexible solution.

 

[Capt W]

Everything I've studied states the correct way is to use backer rod and sealant to achieve an hourglass shape:
https://www.emseal.com/article/hour-glass-tension-backer-rod-caulk-sealant/

There's this stuff also (no experience with): https://www.trim-a-slab.com/how-it-works/
View attachment 306170View attachment 306171

The backer rod is a good idea, and will take less time than measuring and cutting wood. Most of my joints are in the 1" range, but one of them is approaching 1-1/4". Is it better to have a little gap on each side of the rod (allowing sealant to flow down), or should I smash in larger rod? Larger rod will obviously "square up" on the sides, but will be more of a snug fit and will probably require less sealant.