Can You Pour New Concrete Over Old Concrete?

In most cases, the answer is YES! You can do that, but the existing slab must fulfill certain conditions to support a new concrete layer.

Talking of concrete, who wouldn’t love to see a squeaky clean patio or driveway every day? But, we all know how hard it is to maintain concrete surfaces. And, once it starts showing up imperfections – those patches, grime, and cracks look very unsightly. Moreover, daily wear and tear leaves it looking dirty and worn out, which impacts the aesthetics of one’s home or commercial property. That’s why, if concrete surfaces need refreshing, many would suggest ripping out the existing one and getting it redone altogether. However, it ideally isn’t the right option both in terms of money and time. So, you may ask if pouring new concrete over the old one is a better option. We’d say, no, since concrete doesn’t have any bonding agents of its own to grip onto the new layer, but it’s a yes if you get a layer in between the two and help the top layer adhere to the surface beneath.

Let’s guide you through the basics of this process and tell you why it’s a doable thing…can you pour new concrete over old concrete

Pouring Concrete over the Existing One

Here’s the catch – if the existing surface is somewhat in a structurally sound shape and elevating its height to a few inches won’t be a problem, you can certainly freshen it up with a new layer of concrete. However, proper prep work is needed. Anybody can get rid of the existing surface to develop a new one from start to end. But, only a professional can understand and cater to the needs of restructuring. Layering new concrete over old isn’t a durable option only when the materials used are of poor quality, or if one skips the binding procedure.

As mentioned earlier, concrete in itself doesn’t have any binding properties to take the load of an additional (new) layer. So, if you pour new concrete over the old surface without preparing the one beneath, it will crumble within no time and will lead to another big headache. No matter how hard concrete gets or how strong it is, there is nothing that can stick it to the older surface.

So what can be done? If you plan on pouring some or a lot of fresh concrete on the existing slab, you cannot miss out on this step – adding a priming coat. A thin overlay, also frequently called as a primer coating, is put onto the existing surface to prime it up. This consists of special bonding agents that help both the new and the old layer to grip together much firmly and for a longer time giving you a new and sturdy concrete foundation.

The rule of thumb is – If the new layer of concrete is going to be less than 3 inches in thickness, it would need a bonding agent to seal the layers together. And, if the new layer of concrete would be more than 3 inches in width, it would not need a binding agent, but a bond breaker.

So, to know all the steps involved in pouring fresh concrete onto the existing base, keep reading further.

The Process of Pouring New Concrete

Step 1: Cleaning Old Concrete Surface

You can sweep off the dirt or debris on the existing surface, use a pressure washer if there are stubborn stains, or apply chemical-based cleaners to scrub any remaining marks, and leave the surface all wet. A completely dry surface won’t make an ideal canvas to work on. Since concrete is porous, the older layer will absorb moisture from the new concrete, and you’d not want that to happen.

Step 2: Setting up the Perimeter

Correctly measure the space where you’d want to fill the new concrete, mark the needed height, and accordingly estimate how much concrete would be required. You can also install braces to avoid spillage when you begin pouring the new concrete over the old surface. Plus, you can lay a mesh, so you have a precise framework, and it also strengthens the foundation. Also, if the old surface has a lot of cracks, you can use a thin layer of sand, crushed stones, roofing felt paper, plastic sheeting, or Styrofoam.

Step 3: Pouring a Primer

If necessary, level the exiting slab with additives, and then work on dumping a really thin layer of the scratch coat. This is a mix of water and concrete in 1:7 parts (having a liquid consistency), and it is with this mix that you must prime the existing slab for smoothening and prepping it up.

Step 4: Adding the Top Layer

You can additionally mix a bonding adhesive in the final concrete layer to ensure it sticks well. Finally, new concrete is poured over the primer to fill the area you measured. Just make sure that you add it all right away, so there aren’t any chances of the mixture drying out. And, do not forget to level it out nicely, so it looks uniform.

You can end the process by spraying a curing compound onto the final layer. It helps preserve wet concrete and is done right after pouring the new layer.

There are situations when pouring new concrete isn’t the most suitable option. For instance, surfaces with larger cracks, heaving or settling conditions, or where height cannot be raised, replacement is a better solution. However, in most cases, you can pour a new layer of concrete onto the existing one.

For this purpose, if you’d like to contact a reliable ready mix concrete provider anywhere in or around Texas, we can help.

Why Choose T&T Redi Mix LLC?

At T&T Redi Mix LLC, we are committed to providing the best quality materials for commercial, residential, retail, and municipal projects. Whether you require the delivery of superior concrete for building a solid foundation for your home or office space or simply need to restore an existing driveway, we have got you covered. Let T&T Redi Mix LLC supply your next pour! Contact us online or call us today at (214) 785-8037.