Caulking/Sealing Concrete Expansion Joints

[EastTexFrank]

Bird, many years ago in Dallas, when I was having the patio around the pool redone, they filled the cracks between the flagstones with a grouting compound and then pored sand over the top of it. They came back next day and swept the loose sand up. It gave the grouting material a nice finish. Much better than just the straight grout.

 

[JB4310]

I have concrete driveways that I guess are 18 years old. As I guess is common, they were built with wood (1 x 2?) in the expansion joints. That wood has rotted and much of it is missing. So dirt, leaves, grass clippings, etc. gets in the cracks. Yesterday I noticed a pedestrian sidewalk at an outlet mall that has some kind of gray, rubbery stuff in the joints. Can someone tell me what that stuff is and where to get it, or tell me something better to use?

Bird, My first guess would be polyurethane caulk. "Gray, rubbery joint sealer", sounds like Sikaflex 1A, color limestone, it's pretty much the industry standard around here.

http://www.sikacorp.com/tds-cpd-sikaflex1a-us.pdf


It comes in a caulking tube, it does take a little bit of a skill level to make it come out nice and even over a long joint, but if you have ever done any kind of caulking where you had to "tool" the joint, you'd be fine.

I can't compare it to the self leveling stuff cause I've never used it, but this caulk is a premium construction material, we use it in the most demanding applications like flashings, sills, lintels, vertical and horizontal expansion joints, capstones on parapets.

I just did a little reading (in the middle of this reply) on those Polyether self leveling materials and they sound pretty good also. might be just what you need.

What ever you choose, Good Luck, one tip when your doing a job like that is to mask the top edges of the joint with tape, gives you a nice straight line and keeps surrounding surfaces clean.

JB

 

[Bird]

The stuff I got at Home Depot is Sikaflex SL. Since it also says "Professional Self Levelling" it appears obvious as to what the "SL" stands for, but I have no idea what the difference is from the Sikaflex 1A. But this stuff is in a tube to be dispensed with a caulking gun, however, it says to dam both ends of your crevice, no trowling required, for horizontal cracks, not to be used on slopes, etc. so I expect it to be pretty thin when it comes out of the tube.

I can't say I've had a lot of experience with caulking, but I've had more than I wanted.

 

[JB4310]

Sounds like good stuff, it is a polyurethane, only designed for that one horizontal application.

http://www.sikaconstruction.com/tds-cpd-Sikaflex1CSL-us.pdf

Just make sure you have the bottom sealed off good with the backer rod or else the stuff will just "drain" out, it will find any void to fill in. The trick is gonna be to put enough in to fill it close to the top without spilling over and making a mess. The more level the joint is the easier it will be.

If you have trouble finding the backer rod at HD it's usually where the weather stripping is not where the caulks and sealants are sold, at least that's where it is in the HD here.

 

[Scooby074]

Sikaflex 1A is usually what i use. I havent tried the Sl .

But some advise, check the expiry date on the tube (i think its on the bottom IIRC). Depending on your particular HD location they might not have enough turnover to keep fresh product on the shelf.

 

[Bird]

If you have trouble finding the backer rod at HD it's usually where the weather stripping is not where the caulks and sealants are sold, at least that's where it is in the HD here.

Interesting that you would mention that. I looked on the Home Depot and Lowes websites and neither one showed "backing rod". So at Home Depot, on the shelves with the motar mix and caulks for cement and asphalt, I was hunting the backing rod; couldn't find any. So I went to the contractor's counter and a nice gentleman there said it should be right there on that shelf. So he and I went together to look and couldn't find it. He said someone must have moved it or maybe they were out. So he went back to his computer and finally said it showed they had 18 packages of 20' rolls. He said they only stock the 3/4" size. So we went looking again and he finally saw a box way up at the top shelf that was labelled "Backer Rod". So then he had to go hunting a ladder. And as he was coming back down the aisle with a ladder, I turned around and just happened to notice packages of Backer Rod hanging on a bracket at eye level on the other side of that same aisle.

But some advise, check the expiry date on the tube

Now that would sound like some logical advice, so you've had me examining these tubes with a bright light and a magnifying glass and if there's an expiration date on them, I sure can't find it. There's a "Code" number and a "Lot Number" but no dates that I can find.

 

[JB4310]

He said they only stock the 3/4" size.

You said you have pretty big joints, but I will tell you that stuff is a royal pain to work with if it's to big. It can be cut, also a pain, but be careful compressing it to much cause it will spring back up and push your material out or at least make a lumpy looking finished product.

Scooby074 mentioned shelf life, that is one of the negatives with the 1a anyway, I've thrown alot of tubes of caulk away being unable to gun it when it gets to hard. It has a painfully short shelf life, I've got a half case now left over from a job this season, customer paid for it but I know if I don't use it soon it will go to waste, will be no good next season.

JB.

 

[2manyrocks]

What is the life expectancy of this sealant v. putting in trex or PT?

 

[Somervillian]

Bird--
Some of the advice you are getting here is good. Some is not. DO NOT replace the rotted joints with wood or trex (both will rot out again). Definately do not replace with mortar or concrete mix, as this will defeat the purpose of the expansion joint. The backer-rod from Home Depot a good option, though we use sand for a less expensive alternative (this will also help deal with the nails/wire weld mesh you are encountering in some of the joints). Sika is a really good product for this application, even for the wider points. Some local pool supplys may have aless expensive alternative such as deck-o seal. I would recommend that you pressurewash each joint to be caulked first, then sand, then caulk--about 1/2" deep. If you wish, you can "seed" the top of the caulk with sand to give it a mortar-like appearance, without impeding its flexibilty. Simply sprinkle the sand over the caulk once it is tacky, and leave until caulk has cured, then use blower to remove excess sand. We use this method every day with great success. Good Luck!

 

[marimus]

Butyl Mastic.

It skins, however the interior remains soft and flexible, perfect for expansion joints in concrete.

Good for 3/4" joints too unlike silicone.