What Is A Concrete Bonding?
What Is A Concrete Bonding?
Concrete Bonding refers to the interaction between the concrete and the reinforcing material, such as steel or polymer, and the adhesion of the cement paste to the aggregate. Bond is important in order to resist tensile and shear stresses within the concrete.
Bond can also refer to the adhesive force between two hardened concrete surfaces, which can be improved through the use of cement paste or bonding agents.
Bond is critical to the strength and integrity of concrete structures, as exceeding the bond stress can result in cracking, delamination, or the pull-out of reinforcing bars.
In masonry, bond refers to the patterns formed by the exposed faces of the units, such as running bond or Flemish bond.
Concrete Bonding Agents
Concrete bonding agents are used to connect two concrete surfaces, either old or new, or two layers of fresh concrete. They can be made from natural or synthetic materials and help the connected surfaces behave as a single unit. In this article, we will discuss the properties, functions, and types of concrete bonding agents.
Functions Of Concrete Bonding Agent
Bonding agents are used in concrete to improve the bond strength between old and new concrete surfaces or between successive layers of concrete. Without a bonding agent, the fresh concrete will not effectively adhere to the old concrete and will not behave as a single unit, which can affect the overall strength and performance of the structure.
Bonding agents are commonly used in concrete repairs to help the new concrete fill in gaps and damage caused by wear and tear.
To ensure that the new layer of concrete adheres properly to the old surface, a bonding agent is applied to the existing concrete. T
here are two key factors that can impact the bond between the old and new concrete: the cleanliness and preparation of the existing surface, and the strength and condition of the old surface.
Types of Bonding Agents
There are various concrete bonding agents available. These are;
1. Epoxy Bonding Agents
This resin is well-suited for use in the creation of high-performance, lightweight concrete parts due to its fast wetting-out properties and ability to provide high compressive strength, strong adhesion, and high resistance to chemicals. It can be used not only to bond concrete layers together, but also to join concrete and steel components.
2. Acrylic Latex Bonding Agents
Acrylic latex is a polymer blend that appears milky white in color and has a solids content of 45%. This agent is primarily used to bond fresh concrete with a surface of old concrete. These are a combination of polymers and copolymers which is milky white in color. Acrylic latex bonding agents are applied on the surface either by brush, or trowels or rollers.
3. Polyvinyl Acetate (PVA)
Polyvinyl Acetate is an agent suitable for small concrete repair projects because it can effectively decrease the ability of water to pass through and has water-resistant solid properties. It is also popular because it can be used with cement. PVA has good water resistance, and stability when exposed to ultraviolet light, and maintains its properties over time.
Characteristics of Bonding Agents
Some notable features of bonding agents include their ease of application, ability to reduce cracking due to shrinkage, reduction of concrete permeability, enhancement of adhesion between layers of concrete, improvement of tensile, flexural, and bond strength, and resistance to frost and chemical degradation.
How to Use Concrete Bonding Agent?
The procedure for applying a bonding agent is as follows.
- To ensure that a bonding agent adheres effectively, it is necessary to clean the surface of any contaminants such as dust, dirt, oil, or efflorescence. This can be done using pressure washing or vacuum shot blasting to remove excess dirt.
- To prepare the admixture, shake the chemical before use and then mix it with water according to the manufacturer’s guidelines. It is important to follow the application procedures carefully to ensure proper use of the admixture on the cleaned concrete surface.
- The next step is to properly mix the mixture. Refer to the manufacturer’s guidelines for the recommended time frame in which to apply the mix after diluting the chemical with water.
- A layer of bonding agent is applied to the existing surface, and then fresh concrete mix is placed on top of it. The concrete must be poured before the bonding agent begins to dry.
- The concrete layer is smoothed with a trowel after it has been placed, and then cured.
