I had an older driveway poured on compacted gravel. Below that is riversand (we live in a riverdelta). Over the years the concrete driveway developed cracks but no significant breakups. The thickness is 4″.
Rather than taking the driveway out (disposal fees are horrendous) I poured another 4″ on top of the old driveway with the usual control joints.
Now I discover that where the cartires sit in their usual location the concrete developed sags and when it rains there are now puddles on the once level driveway.
Can concrete bend like that?
Replies
yep, if you did not let it cure for more than a few days before parking the car on it......
Yes Indeed!
concrete is plastic until it has reached over 90% of its final cure strength.
ommon for it to warp too, like a wet pine board laid out in the hot sun. Measures need to be taken to make sure that it cures properly.
can concrete bend
I guess three weeks no parking was not good enough.
thanks for the info
If the top cures faster than the bottom of the slab it will want to curl up since the top surface shinks more than the lower - don't know if that's what happened butThis is more common if there is a membrane or in your case another slab under the new one since it retains moisture well on the bottom of the new slab. Direct sun, lack of moisture barrier (sprayed on or otherwise) on top of new slab doesn't help. Tapping the concrete probably produces some hollow spots where the new and old slabs have a slight gap and some solid spots (under your tires and along the middle of the slab).