Replacing concrete expansion joint filler

Novice here...need some advice.

I have and expansion joint in between my driveway and garage. The joint is approx. 3/4 to 1" wide and 4" deep and 25' long. The current filler, which is some sort of compressed fiber type material, is rotting away and I'm looking to replace it.

Stopped by Home Depot, and they told me I should use a backer rod and self-leveling sealant.

They sell 0.5"wide 5' long expansion joint fillers, which appear to be the same material that I have in there now. But the guy said it's virtually impossible to insert them into the joint.

Being a novice, and not wanting to mess things up, I'm looking for clarification.

My thought would be to remove the existing, rotting materials, clean out the joint, and insert the closed cell backer rod. However, the backer rod is is only 3/4".

Do I need to insert the backer rod all the way to the bottom of the joint? If so, that'll leave more than 3" of open space to be filled with self-leveling sealant...which would cost a fortune!

Can I put multiple layers of backer rods on top of each other, leaving about 1/2" or so from the top of the concrete to fill with the sealant? Or can in insert the backer rod to just about 1/2" below the top of the concrete, leaving open space below the bottom of the backer rod?

If I can put multiple backer rods on top of each other, it'd make for a better financial decisions, as a package of the 3/4" backer rods are only about $6...I could put 3 or 4 rows on top of each other for about $30, which is a lot less expensive than putting in 3+ inches of sealant for the entire 25 feet length.

Thanks in advance for your support! And again, I'm quite the novice so easy, simple, plain English feedback/instructions are greatly appreciated!

 

Why do you think it needs to be replaced?
It's only there to allow the slab to float.
Really want to seal it up there is no need to fill the whole gap, one row of foam backer then the sealer will work fine.

 

You should be able to find 1" backer rod if you look hard enough. A ready-mix plant should have it... also contractor building supply stores. 1" backer rod gets pushed down 1/2", so you only need to clean out the top 1 1/2" of the joint. A grinder and a thick tuck pointing masonry grinder blade would work good if you need to grind the joints out to clean them. Putting 2 backer rods together might work in a pinch if you have to. But it's also an unecessary pita if you ask me.

 

Thanks for your response! I'm not sure I have a compelling reason to replace other than to try and keep dirt and debris from collecting in the joint. Since there is material in there now, I'll see if I can remove and go with one row of backer rod and sealant. Appreciate you taking the time to respond!

 

Thank you X for your input! I did a little searching to see if I could find 1" backer rod, which is what I'll need for the job. If I can get some that'll make the job easier, especially if I don't have to remove all the remaining filler. Again, I sincerely appreciate your help!

 

It works best to leave the top of the backer rod about 5/8" below the finished surface. That way, you can place about 3/8" of liquid sealant, leaving the top of it about 1/4" below the riding surface. You don't want it to be flush with the surface, or come hot weather, it will bulge over and be tracked all over tarnation by tires passing over it. Trust me, doing so creates a mess you won't soon forget.

 

BridgeMan, excellent advice! I'm sorry that you had to experience that but thanks for helping the rest of us learn from it!