How to Adhere Concrete to Concrete

Monsoon50

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posted on 12 years ago — updated on 1 second ago

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Concrete is usually made of cement, water, gravel, and sand. This combination creates a very hard, durable surface. However, cracks and damage can occur. Fixing concrete takes a number of materials because it does not readily adhere to other concrete. The mixture and formation relies on a chemical reaction that stops once dried. If you need to patch a concrete surface or pour new concrete on top of old concrete, you must invest in a strong bonding agent and a concrete patching mix. If all precautions are taken, you can create a repair that will last a few decades.

Steps

Patching a Concrete Surface

Wait for a cool, overcast day to do your concrete repairs. This is the best time to adhere the concrete because it takes longer for the water to dry out, and it has more time to react with the cement.

Buy concrete patching material. It is available in a pre-mixed form or by buying the separate ingredients in bulk. If you haven't adhered concrete to concrete before, it is a good idea to go with the pre-mixed version, which only requires that you add water. Buying the raw materials, gravel, Portland cement and sand is considerably cheaper than buying pre-mixed concrete patching. If you are patching a deep hole, you can use 1-inch (2.54-cm) gravel, otherwise, use very fine gravel. Mix the dry materials in a ratio of 3 parts gravel to 2 parts sand to 1.5 parts cement in a bucket. This is sometimes listed as 3 to 2 to 1. A higher amount of cement will create a stronger material. There will be more of chemical reaction between the cement and water, which will create more crystals and a harder structure.

Sweep the concrete surface carefully. You must remove all loose stones, or the bonding agent and cement will not reach the surface of the concrete.

Dust the surface thoroughly after you have swept. You can use a blower or a soft brush; wipe away the dirt that is stuck to the surface.

Rinse the concrete. Sprinkle an even amount of water onto the surface with a hose attachment. Stop adding water before you create standing water on the surface. This will stop the porous concrete from sucking the moisture out of the bonding agent and concrete bonding material.

Create cement paint. Mix Portland cement, which is available at most hardware stores, with water. Stir the 2 ingredients together until they form the consistency of wet paint. You can also buy an acrylic bonding agent to use in place of the homemade cement paint. They are made of resin and can be either added to your patching concrete or applied like the cement paint. Follow the instructions on the can or bottle very carefully, as many of the products have different application instructions and drying times.

Apply a thin layer of the cement paint to the old, damp concrete with a paint brush. Do this right before you plan to pour the new concrete patch onto your old concrete surface.

Add the water to the homemade or pre-mixed concrete patch just before applying. Mix it well. Pour the patch into holes and cracks or pour a 3/8-inch (1-cm) layer to flat surfaces.

Wipe the surface of the concrete with a wooden float. Apply it to the surface with a back and forth motion until the pieces of gravel have sunk below the surface. The sand and cement should rise to the surface.

Allow water to bead and rise to the surface. It will evaporate on its own. For a smoother finish, wait until the concrete is hardening and almost plastic in texture, then apply a smooth back and forth motion with a metal trowel.