Adding new concrete on top of old - bonding agent needed?
#1
10-30-19, 09:19 AM
Adding new concrete on top of old - bonding agent needed?
Hi there. Need some advice on adding new concrete on top of old. In this case “old” is about 3 weeks and has never been exposed to any elements. And it’s not a flat surface...it’s a round concrete ball. Want to know what Prep and products to use to make sure it adheres
I was trying to make a concrete garden feature for my wife’s birthday. It’s a sphere and I used a plastic light globe as the mold. Got the idea from the atlas stones that strong men and CrossFit folks use. It’s cored (3/4” hole) it and it will be a bubbling water feature
Being my first try the sphere is pretty much perfectly round but has some rough spots and voids. I read (again on a strongman site) that you can repair damaged atlas stones with concrete patch product. Smear it into the voids and smooth it out. Buff/sand when dry (24 hours). But as to the steps and products...opinions vary. Some sites say to add a fortifier to the concrete. And others say to paint on a concrete bonding agent/primer. While still others say to make a slurry of primer and sand/concrete as a first layer. Or do all that. Again, most of these are for repairs to stones that are being (potentially) dropped repeatedly and have been exposed, may have cracks etc. Mine is new and undamaged and will be installed and never lifted again....it’s just imperfect. Some imperfection is fine and gives character but I want to fill those voids
Will try to attach some photos in a bit. Advice appreciated!
Thanks!
I was trying to make a concrete garden feature for my wife’s birthday. It’s a sphere and I used a plastic light globe as the mold. Got the idea from the atlas stones that strong men and CrossFit folks use. It’s cored (3/4” hole) it and it will be a bubbling water feature
Being my first try the sphere is pretty much perfectly round but has some rough spots and voids. I read (again on a strongman site) that you can repair damaged atlas stones with concrete patch product. Smear it into the voids and smooth it out. Buff/sand when dry (24 hours). But as to the steps and products...opinions vary. Some sites say to add a fortifier to the concrete. And others say to paint on a concrete bonding agent/primer. While still others say to make a slurry of primer and sand/concrete as a first layer. Or do all that. Again, most of these are for repairs to stones that are being (potentially) dropped repeatedly and have been exposed, may have cracks etc. Mine is new and undamaged and will be installed and never lifted again....it’s just imperfect. Some imperfection is fine and gives character but I want to fill those voids
Will try to attach some photos in a bit. Advice appreciated!
Thanks!
#3
12-14-19, 06:00 AM
Group Moderator
Since it's going to be a fountain and visible I would put extra effort into making the ball perfect from the beginning and do less worrying about fixing blemishes. Any patches for "filling" you do will likely always be visible (and ugly) in your final ball. So do everything you can to make it come out perfect and without needing filling. If the mold is bad your ball will be bad so take the time to smooth any bumps in the mold and fill any voids. Also, make sure your mold is strong enough to retain it's shape when filled.
Before pouring spray or coat the mold with a release to make it easier to remove from the mold. When pouring your concrete vibrate the mold to insure there are no air pockets or voids but don't do so much that you separate the cream from the aggregate.
Before pouring spray or coat the mold with a release to make it easier to remove from the mold. When pouring your concrete vibrate the mold to insure there are no air pockets or voids but don't do so much that you separate the cream from the aggregate.
