![]() ![]() But we are not talking about tearing out the concrete slab, mixing new concrete, and pouring a new one. So, if you trip and fall on your face, you know that this issue needs to be addressed immediately. Also, cracks and holes can be tripping hazards. Remember that in topping work, handling the details makes all the difference.No matter how much we ignore old and ugly concrete surfaces, they would always haunt us every time we walk on or by them. They also have much higher compressive strengths than the concrete mix you are thinking of using. Polymer cements have good flexural and tensile strength ratings and are much more crack-resistant. I suggest that you bring the entire floor up to within 1/2 inch of the top elevation with one product, and then use a product rated for 1/2 inch over everything. So, one product is good for applications in the 0- to 1/8-inch category, another for up to 1/2 inch, and another for 2-inch-thick applications. Most products come packaged for different thickness applications. They will take chemical stains differently, too, if that’s what you intend to use.Īnother approach is to use a polymer-based overlay cement for the entire project. The only problem with this approach is that the floors are likely to be different colors due to the two types of cement, and there will very likely be some efflorescence on the floor that is wet cured. Overlay cements are sticky and require experience in terms of troweling a finish. My recommendation is to staple down diamond mesh over the plywood before placing the overlay. This should provide a slab without cracks, but it’s not a guarantee.ĭon’t try to use a regular concrete mix for the 1/2-inch-thick area or over the plywood, rather use a polymer overlay cement rated for that thickness. You can use a 10x10-foot grid, but 8x8 is better. When you remove the burlene, saw cut the slab immediately. The concrete won’t shrink when it is wet, so it shouldn’t crack during this period. A product like burlene is good for this, but keep it wet. The slurry must not dry before concrete is placed over it.Īfter the concrete is finished, it should be wet-cured for 14 days. Squeegee or sweep with a stiff broom the slurry into the existing floor just ahead of concrete placement. You can use a 50% mix of water and latex bonding agent (like Acryl 60) to make the slurry. Use a 50% mix of portland cement and sand and make a slurry of it. The day before you place concrete, wet down the surface and keep it wet until you place concrete but don’t have any standing water on the slab during placement. The topping mix that you mentioned is OK. Given that the floor is interior, the cracks between the existing concrete and the trenches for plumbing and electrical probably won’t move. Do not use a sandblasted surface it’s not aggressive enough. You will need a very rough profile on the existing floor. First, let’s consider the 2-inch topping. Should I put a bonding agent down for both the concrete-to-concrete pour and the concrete-to-plywood pour? Is it feasible to pour on a plywood deck? This project is going to be an art gallery and I don’t want any problems after the fact.Ī. I am worried about cracking, which would be a problem for a finished exposed concrete floor. The general contractor is going to prepare the floor by sandblasting. We propose to use 3000-psi concrete with 3/8-inch aggregate, a water reducer, a superplasticizer, and polypropylene fibers. ![]() He also wants the roof deck (with a plywood base) to have the same overlay. The client wants the overlay to be the finished product with 4-foot squares cut in the floor for a pattern. The floor varies from a flat plane by 1/2 inch to 3/4 inch. The floor is in different sections and has had plumbing and electrical strips cut in and repoured. We are going to do a 2-inch overlay on an existing concrete floor. ![]()
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