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My concrete pavers cracked! Why?!

I've been installing a patio using Mutual Materials Vancouver Bay slabs in 24"x24". They are 1.75" tall and poured concrete. I excavated, put down geotextile, 4" of 3/4" minus, used plate compactor, put down weedblock, screeded 1" of sand, layed my pavers, installed Snap Edge paver restraint, used plate compactor with pad.

The plate compactor cracked a couple pavers because a small pebble bounced up on a paver and underneath the compactor. Even with the rubber pad it cracked them. However, it did a fantastic job of settling them into the sand and evening the grade out. I replaced the two cracked pavers.

Ok here's where it starts going wrong. I adjusted all the pavers so there was 1/8" gap between them. I used a small pry bar, and 1/8" plastic tile spacers.
At this point all I need to do is get polymeric sand. I couldn't find gray polymeric at the big box stores. I leave for a 4 day camping trip, and figure the pavers will be fine and all I have to do is get the gray polymeric sand from a landscape supply.

While I was gone it rained heavily for the first time since spring. I get back and 10 of the pavers are cracked! Most of them splitting down the middle!

AAAAHHHHHARRRRGHHHHHHhhh!
WHY?!!

My theories so far...
1.) The plate compactor actually caused some weakening of the concrete or micro cracks in the slabs and then when it rained the pavers absorbed water and expanded and those weak spots turned into full on cracks.

2) I left the plastic spacers between the pavers while I was gone. When it rained the pavers absorbed water and expanded and with the plastic spacers between them they were sort of making contact with one another and put pressure on one another causing them to crack. Like spalling where pavers are butted up to one another.

Anyone have an idea? I need to not only replace the broken pavers, but also make sure this doesn't happen again. Do I need to increase the gap between pavers? Is 1/8" to small?
Thanks for your help!      
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Posted 2018-09-14T06:18:15+0000  by PondNGone PondNGone
 

Hi PondNGone.

 

Thank you for your question.

 

Yes, your situation seems to be a bit perplexing.  One of the issues may have been the compactor placed directly on the pavers.  Even with the rubber pad, the 1.75-inch pavers can take a pretty good beating under a heavy plate vibrator.  I would have added sand to the top of the pavers before using the plate vibrator, but then that would have filled in your spaces.

 

The rain may have been an issue if the pavers absorbed water and expanded, especially if they were in pretty tight.  Ground settling after the rain could also be an issued for you.

 

Did anyone jump around on your patio while you were gone?? Kids goofing around???  


Your pavers could of already had micro fractures in them and the compactor just exacerbated the situation.  Then the rain just settled everything and the cracks widened.

 

When you placed the pavers, was your surface flat and level ??  Any small hills or valleys could cause a crack if pressure was placed upon them.

 

Your gap should be adequate at 1/8th of an inch. 

 

Please let us know if we can be of further assistance.

 

Rick_HD_OC

Posted 2018-09-14T20:17:28+0000  by Rick_HD_OC
 
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