Guide to Concrete Adhesion
Posted By:Dynamic Concrete Pumping , Date: Feb 27, 2020
Concrete is known for its strength, but not bonding. Understanding what concrete will stick to — and what it won’t — is essential when you’re repairing old or pouring new concrete. It will help your concrete application go right the first time without causing problems later on.
In this guide, we will explain the science behind concrete adhesion and the various materials it will and will not work with.
How Concrete Adhesion Works
Cement, which is part of the concrete mix, does not have any natural bonding agents. In many cases, freshly poured concrete will not bind to the other material but be separate. For surfaces that are weight-bearing, such as floors and foundations, this issue means lack of a sound structure.
To encourage adhesion between the concrete and the other substance, you’ll need to use a bonding adhesive. After prepping the surface, use a brush, broom, roller or sprayer to apply the bonding agent. Depending on what kind you get, it will keep moisture out and resist wear and tear from traffic.
In some instances, concrete will naturally bond to other materials. To prevent concrete from sticking to these materials, you need to treat them with a release agent to keep the concrete from sticking by forming a thin lubricant film over the material. When the concrete is dry, it’s easy to separate.
A few different kinds of release agent exist, including:
- Oil-based: Chemical blends, like linseed oil, mineral oil and paraffin, make the surface stick-resistant.
- Water-based: This variety is made from plant-based materials, like vegetable oils, and won’t discolor the concrete surface.
- Reactive: The fatty acids in this substance have a chemical reaction with the alkalinity in the concrete to prevent sticking and keep the concrete unstained.
What Will Concrete Stick To?
Concrete does adhere to wood, though the connection is often not ideal. Many builders use wood panels as forms that concrete is poured into to create a foundation or floor. After the concrete is cured and dry, the wood is removed.
In such an application, you would need to use a release agent to make removal easier. Lumber mills often pretreat their wood with oil-based blends to make it stick-resistant. If your wood has not already been treated, you may have to purchase a commercial agent and apply it yourself.
What Will Concrete Not Stick To?
Concrete does not adhere to:
- Concrete – Dried concrete doesn’t have any natural bonding agents, so in order to get wet concrete to bond to existing concrete, a bonding agent will need to be used.
- Molds – Most concrete molds are made from urethane rubbers, which are designed to be resistant to concrete bonding.
- Paint – Paint is another material that has no natural bonding agents, so concrete generally won’t stick to it very well.
- Oil – Oil or oiled surfaces are often used to make the surface resistant to concrete bonding.
To promote adhesion, you’ll have to add the bonding agent yourself to get the concrete to work properly. If you’re repairing existing concrete, you’ll need to get the concrete to bind to these materials so that the repair lasts as long as possible.
Get a Consultation With Dynamic Concrete Pumping
Do you have a concrete project in Alberta that you need to get right? At Dynamic Concrete Pumping, we have more than 40 years of experience working with concrete, and we’ll be happy to consult with you about your project specs. Fill out our contact form today.