What Is a Concrete Bonding Agent?
Concrete bonding agents are natural or artificial materials utilized to join old & new concrete surfaces. This agent can also be utilized to join the successive concrete layers. This bonding agent helps to allow different concrete finishes to behave like a single unit.
These Cement bonding agents are also utilized in various repair works, such as bonding new concrete to old concrete, spraying concrete at construction joints, or cement-sand repair mortar to get a reliable bond.
Why do you need to use a Concrete Bonding Agent in Concrete Mix?
- When the an upper surface of the concrete floor becomes destructed there are generally two choices either demolishing the floor and starting again or resurfacing the existing concrete.
- Replacing the entire concrete floor and resurfacing is become costly, both financially and in terms of time as well. It is also a waste of time & money if the floor is still structurally sound.
- A further solution is to apply the fresh concrete mix on top of the old surface.
- The cement within a concrete mix does not contain any natural bonding agents. So, when fresh concrete is applied on top of an existing layer of concrete, both surfaces won’t join or fix together properly.
- Once the top layer is cured and set, it will simply sit on top as a separate layer. This will not construct a strong serviceable floor.
- Concrete bonding agents are essential to be applied first onto the existing surface of the concrete to ensure that the fresh concrete will successfully adhere.
- This is also true for floor repairs if the concrete is used to fill the gaps caused by damage. The new concrete layer won’t be properly fixed with the old one without the help of the bonding agents.
Characteristics of Concrete/Cement Bonding Agents
The main characteristics of concrete bonding agents are:
- The bonding agents are easy to apply and use.
- They mainly reduce the shrinkage cracks formed on the surface of the concrete.
- The permeability of concrete is reduced.
- Bonding agents enhance the adhesion between the layers of concrete.
- The tensile, flexural, & bond strength of the concrete mix or mortar are increased.
- The bonding agents can withstand frost & chemical actions
Various Functions of Concrete Bonding Agents
- If a new layer of concrete is added to an existing layer, they act as two different layers without proper bonding. So, it is essential to introduce bonding agents between the layers.
- The utilization of concrete bonding agents allows the different concrete layers to behave like one surface, thus increasing the performance and strength of the concrete structure.
- This bonding agent is placed on the existing surface of the concrete so that the new layer of fresh concrete properly joins the old layer.
The two major parameters that can affect the bonding between old and new concrete are:
- Surface preparation and cleanliness of the existing structure
- Strength & integrity of the old surface
How to Use Concrete Bonding Agent
1. Clean the Surface
It is necessary to have a very clean & neat surface. If the existing surface of concrete contains any dust, oil, or grease, effloresces the bonding agent will not work properly.
So, the first step is very essential to make sure that the bonding agent works well on the concrete surface. Perfect cleaning can be achieved by pressure washing or vacuum shot blasting.
2. Prepare the Admixture
The vessel of the concrete bonding agent must be trembling well before use. Then, the chemical must be poured in a proper amount into a separate bowl & diluted with water as per the required consistency.
The whole mixture must be mixed properly. This mixture can be utilized as a primer. However, it is advised to follow the manufacturer’s instructions to decide on the proportions.
The next step is mixing. The concrete bonding agent is required to be mixed properly & thoroughly. Reading the instructions mentioned on the container is a must.
The amount & time for application (after the container is opened) given on the container must be followed. It must be kept in mind that the amount and time differ for different types of bonding agents.
Improper mixing techniques can cause damage to the concrete surface, or the concrete chemical might not work properly. Hence it is very essential to follow the instructions as specified by the related company.
4. Applying the Concrete Bonding Agent
Once, if the concrete mix is prepared by adding the bonding agent, it must be applied on the surface immediately. If more time has passed, the primary coating may dry off losing its adhesion.
Hence, the concrete mix has to be placed when the chemical is still tacky & not completely dry. For mixing and laying of the concrete, standard specifications must be followed, once the application is completed, smoothen the surface with the help of a trowel and allow it to cure.
Different Types of Concrete Bonding Agent Used in Construction
Different concrete bonding agents used in construction are:
1. Latex Emulsions
In cementitious compositions, latex emulsions are commonly utilized as oil-in-water type emulsions. Latex emulsions are classified into 3 types with some compositions containing more than 50% water. Some bonding agents also have more resistance to water than others.
The constitution of latex emulsions is stable in water & cement systems though not all emulsions are compatible with cement. Therefore, to choose the suitable latex emulsion for your work, you need to understand its chemistry.
Utilizing the latex emulsion agent without cement in the concrete mix will result in a failure plane as there is no film produced at the bond interface.
However, there are 3 ways to change the latex emulsions into useful bonding agents:
- Make a properly mixed cement slurry with latex forming part of the mixing water.
- Add one part of water to the one part of latex emulsion diluted material.
- Utilize re-emulsifiable latex as it can be rewetted & softened when it gets in contact with water.
2. Acrylic Latex Bonding Agent
Acrylic latex is mainly utilized in the bonding of fresh concrete to the old surface. This milky white latex emulsion comprises 45% solid content. Apply it on the surface with either a brush, broom, spray, roller, or trowel.
3. Styrene Butadiene (SBR) Latex
SBR is a kind of latex emulsion agent that is a co-polymer & compatible with cementitious compounds. This SBR concrete bonding agent is milky white in appearance & contains 55% solid content.
SBR latex can be utilized for the following functions:
- Bonding fresh concrete to the old concrete surface.
- Bonding fresh concrete to a thin layer.
- As a layer for the plaster to bond within 45 minutes.
4. Polyvinyl Acetate (PVA) Latex
There are 2 types of PVA Latex emulsion:
1. Non-Re-Emulsifiable PVA: It is commonly used as a bonding agent because of its compatibility with cement. This PVA latex can also be utilized as a binder for cementitious water-based paints & waterproofing coatings. After being applied, this bonding agent built a thin layer that is highly resistant to water, aging, and ultraviolet rays.
2. Emulsifiable PVA: Once an emulsifiable PVA is applied on the surface, it produces a film that can be softened & rewetted with water if necessary. The film can also be laid long before the application of a water-based overlay on the concrete surfaces. This PVA latex is utilized as a bonding agent for plaster. Moreover, emulsifiable PVA is utilized to bond finisher base-coat gypsum to the interior surfaces of cured cast-in-place concrete.
Utilization of Polyvinyl Acetate Latex (PVA) is limited to areas where there is no possibility of infiltration of moisture to the bond line.
5. Epoxy Resin
Epoxy resin is popular for being the most versatile of all concrete bonding agents. The epoxy resin is ideal for high-performance & lightweight parts.
It is characterized as being strong but brittle. Epoxy resin can be produced to become more flexible without losing its tensile strength.
Epoxy resin is a concrete bonding agent broadly utilized in the construction field because of its high compressive strength, chemical resistance & strong adhesion.
Epoxy resin has a versatile bonding ability like, that wets out quickly, and can be used for bonding to a variety of materials as long as the surface is well-prepared.
Some of the properties that epoxy resin gives for excellent adhesion characteristics include:
- Cured epoxy resins give tensile and compressive strengths higher than concrete.
- Epoxy resin compounds do not contain any volatile solvents. The liquid resin becomes 100% solids after curing.
- Epoxy resin is able to adhere to almost all construction materials.
- At the time of the curing period, epoxy resins do not produce any by-products.
- Shrinkage cracks during or after curing are minimal.
- Once cured, epoxies have dimensional stability.
Epoxy Resin is used for:
- For bonding fresh concrete to an old concrete surface.
- For bonding of concrete to steel.
- Can be p
- produced to cure at room temperature & elevated temperatures, under wet or dry conditions.
- For repairing concrete and spalls and other defects such as cracks in concrete.
Damage to a concrete surface leaves you with two options; first either demolish it or to re-surface. Removing the old concrete and pouring fresh concrete is time-consuming and more costly.
The best solution would be to re-surface the old concrete with a layer of fresh concrete mix. Though, the new layer of concrete will settle on top of the old surface as a separate layer.
You should first apply the concrete bonding agent to the damaged surface. The new layer of concrete will then stick appropriately to the old layer, forming a single unit.
Why is concrete bonding important?
Concrete bonding is important because it ensures that the two pieces of concrete are joined together securely, which can help to prevent structural failure and ensure the longevity of the concrete structure.
What are the different types of concrete bonding?
There are two main types of concrete bonding: mechanical bonding and chemical bonding. Mechanical bonding involves creating a physical connection between the two pieces of concrete, while chemical bonding involves creating a chemical reaction between the bonding agent and the concrete.
How can I improve the bond strength of concrete?
To improve the bond strength of concrete, it is important to ensure that the surface of the concrete is clean and free from any debris or contaminants. It is also important to choose the right type of bonding agent for the specific application and to follow the manufacturer’s instructions carefully.
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