However, there are also some downsides that we’ll identify. There are advantages to pouring concrete over concrete. Pouring Concrete Over Concrete: Pros and Cons But for bonding agents to work properly, the existing layer of concrete needs to be free of fine aggregates or dust, and contaminants like grease and oil. Bonding agents are also necessary when using new concrete to repair gaps and significant cracks in the existing concrete. You must apply bonding adhesives (bonding agents) onto the original concrete before pouring the new layer for it to adhere properly. The new layer of concrete will sit on top of the old layer but not fuse, causing the material to be weaker than the original layer. Without this help, pouring a new layer of concrete will result in two separate layers. Bonding agents help concrete stick to a surface, including old concrete. While you can pour concrete over concrete, you will need to use a bonding agent with the new concrete because the cement inside the concrete doesn’t have its own. For it to be possible to pour concrete over concrete, the existing layer of material must be in good condition and properly prepped. Whatever issue causing severe structural damage to the existing layer of concrete can also do the same damage to the newly poured layer of concrete. Likewise, if tree roots are causing the old foundation or pad to heave, or lift, a new slab won’t make matter. Problems like cracks, discoloration, frost heaves, deterioration (crumbling), or a slab that’s settled to different uneven levels cannot be fixed by pouring a new concrete slab over the top. If there are any signs of damage on the old concrete, you will need to address the flaws before pouring a new layer. However, before you head out to pour a new layer of concrete over your existing layer, you’ll need to check the condition of your old slab. We’ve already let the cat out of the bag and stated that you can pour concrete over concrete, so the quick answer is, Yes. Concrete Thickness Overlay on Old Concrete.How to Pour Concrete On Top of Concrete.Pouring Concrete Over Concrete: Pros and Cons.Will New Concrete Stick to Old Concrete?.How? Simply click here to return to Concrete Overlay Questions. Join in and write your own page! It's easy to do. You can check out their website for more information or call them for technical assistance. We use a lot of Mapai products for overlays. If you are laying another floor over the concrete overlay then it should be good enough for that. If the self-leveling overlay is the finished floor then you may need to install a micro-topping material over it to hide the pin holes left by the air bubbles. It may be necessary to saturate the sub-base material with the primer and mop up any that puddles. If the sub-base material is really porous, then one coat of primer may not be sufficient. The water replaces the air in those voids, pushing it to the surface causing tiny air bubbles. The second reason air bubbles form is when the overlay material is laid down on the sub-base, the mix water in the overlay material settles into the tiny voids in the sub-base. The first is over mixing the product, using the wrong mixing paddle, and moving the mixing paddle in and out of the material while mixing it.ĭoing this traps air in the overlay material and once the material is laid down the air escapes through the surface causing tiny bubbles. The air bubbles can appear for a couple of reasons. Air bubbles in concrete overlays are a common problem. They had 1 guy who's job was to maintain consistency of the product by mix time and adding a wee bit of water if needed.Ī. What can be done to fix this? Will they have to do another overlay? The temperature was about 70 degrees, low humidity, a/c was off and no windows open, just doors and no wind blowing. After about an hour I went back to where they started and I saw many, many holes in the overlay where the air bubbles popped after the overlay had self leveled. I watched as they continued and some buckets had more bubbles than others. The bubbles started popping pretty soon after the mix was put down. I noticed many air bubbles in the overlay. The first bucket of overlay was just a bit too thick so they added a bit more water to the mix. the concrete floor was cleaned very well, dried and primer put down. I had an overlay installed inside a house we are doing a remodel on.
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