Polymeric sand to treat cracks in concrete patio?

[stickshift]

I've got some cracks in an old concrete patio, and of course I get weeds every year that I beat back with a string trimmer. I'm not ready to replace the entire patio with pavers, but wondering if using a power washer to clean out the cracks and brushing in polymeric sand and sprinkling some water will keep the weeds at bay for a few years? Or powerwash, let dry and apply sikaflex? I've used sikaflex before in a different area, and I don't think it looks good. Thinking sand might look better, as in less noticeable to the casual eye. Sikaflex is very noticeable.

 

[Stuart in MN]

It may work for a little while but the weeds will come back pretty quickly, polymeric sand won't stop them.

 

[CraigStu]

Are the cracks wide enough that you could work something like a grout down into them?

 

[stickshift]

Are the cracks wide enough that you could work something like a grout down into them?

Yeah, some of them - the ones with the most dense clusters of weeds.

 

[58Yeoman]

We have a small "island" of flagstone around two shepherds hooks with bird feeders on them, and I used polymeric sand between the flagstone twice. Didn't work. The moles will come and push it up or the weeds will come through eventually. We just had our front porch and sidewalk replaced and the workers had to remove our island to get the heavy equipment in there. They put it back together, and I filled the spaces with pea gravel and then used the landscape glue to keep that in place. Time will tell if that works better. I think it will.

 

[Stuart in MN]

I think the wider the gap, the less polymeric sand is going to work. It's great if you have concrete pavers that are butted up against each other, but for the wide gaps between flagstones not so much. My front sidewalk is brick with gaps of about 3/8". The sidewalk is original to my 1913 house, the original mortar in the gaps is long gone so I put in polymeric sand. It's held up reasonably well but I do need to go over the walk a few times each summer with the string trimmer to fight back weeds that have taken root.

 

[Kaizen]

maybe pics would help as the number of cracks and size of slab definitley play into the decision.
I use polymeric on my 24x20 patio pavers. I just pressure washed the old stuff out and laid another 6 or so bags last year as I was rehabbing some pavers. It lasts like ten years imo before getting bad. Weeds will top seed but i just hit them with the string trimmer or weed killer. I would say after polymeric i have about 90-95 percent less weeds then with just sand. Be aware its only in a few colors so not sure if it would stand out. I did notice the home depot stuff sucked vs the stuff at the stone yard. Both worked but stone yard flowed way nicer into cracks.
If its not many i think i'd spend the time putting foam backer rod and silkaflex. If you do it on a warm day you can get that stuff to flow out like paint so its level with the concrete. Again the color thing needs to be investigated. Being you are in the northeast those slabs are going to lift with the frost so i don't think either are gaurenteed. I know silka will stretch but not sure how far.

 

[lund]

Sikaflex and similar products may be better if you live in a cold climate. Water gets in cracks some seasons and will freeze opening up cracks more and potentially frost heaving the ground underneath. Sand of any type will be less water tight than something like Sikaflex. I live in Michigan and did this on driveways, walkways, and the sidewalk because I got sick of cutting down weeds in all the cracks. Sikaflex can last about 8 ish years before needing to touch up and it avoids a LOT of weeding and string trimming year by year (damn weeds find everything quickly). Plus it helps avoid more cracks and damage in the winter. I am less concerned on exact matches. But if you are lucky, some of the standard colors might be close enough to be less noticeable.

With Sikaflex, I pick out the crack using a bent hook like a cotter pin puller and then wire brush and vacuum. Maybe power wash lightly and let it dry well. Then I put Sikaflex in with a board covering the seam for a few days (on sidewalks) so nobody walks on the seams while they are curing. It takes some time so I do a few seams a week on weekends. But it beats weeding regularly all growing season and keeps the concrete from further degrading and frost heaving near cracks and seams. I tend to not use backer rod unless the cracks are very wide. So, if the cracks are wider, I sometimes do a few passes of filling to account for shrinkage in the curing process. It also works better to do this on warm days since Sikaflex flows into the cracks much better when hot. I hate yard work and this helped me avoid some of it overall.

 

[CraigStu]

Seems like a perfect use of Roundup or your favorite similar product. Isn't there some common home use chemical like vinegar that kills weeds?

 

[rlitman]

It may work for a little while but the weeds will come back pretty quickly, polymeric sand won't stop them.

It's done pretty good for me, but Sikaflex has way more stretch.

...I've used sikaflex before in a different area, and I don't think it looks good...

Put down the Sikaflex SL, and then sprinkle sand on top of the wet self-leveling caulk. Or if you can get crushed concrete or granite dust or anything more grey than sand, it might hide even better.

 

[afinepoint]

I've got some cracks in an old concrete patio, and of course I get weeds every year that I beat back with a string trimmer. I'm not ready to replace the entire patio with pavers, but wondering if using a power washer to clean out the cracks and brushing in polymeric sand and sprinkling some water will keep the weeds at bay for a few years? Or powerwash, let dry and apply sikaflex? I've used sikaflex before in a different area, and I don't think it looks good. Thinking sand might look better, as in less noticeable to the casual eye. Sikaflex is very noticeable.

Follow instructions closely. Do not apply if there is the slightest chance of rain.

It has its lovers and haters. Seems more of the latter. Biggest complaint is it's a mess to put down. Any granules missed and not sweeped into the gaps or off the patio will adhere to the stone's surface degrading the look you paid or worked hard to create.

I pressure wash annually using a concrete cleaning attachment then sweep new sand back in.

 

[Kaizen]

Follow instructions closely. Do not apply if there is the slightest chance of rain.

It has its lovers and haters. Seems more of the latter. Biggest complaint is it's a mess to put down. Any granules missed and not sweeped into the gaps or off the patio will adhere to the stone's surface degrading the look you paid or worked hard to create.

I pressure wash annually using a concrete cleaning attachment then sweep new sand back in.

I'll add to this. Make sure you have a working leaf blower to blow it off after sweeping. last time i did it i could not start mine and rain coming in fast. made it go HD and grabbed an electric. That was a close mess. Also put down the polymeric before you put a sealer on. Last time i did it i sealed first and the sand removed/covered some of the sealer shine that i wanted.

 

[mm08822]

Best yet is a plate ******** (or equivalent) to work it deep into the joints. Buys a little more time from weeds.

(I know, how many of us have a plate ******** just waitin for some work.)