What Is Bond Breaker?
In the modern construction industry, the term “prefabrication” or “precast” holds a significant value. Concrete elements are generally of two types; those are Precast and cast-in-situ construction. If the Precast construction, the concrete is cast at a place other than the site, which is when required, are brought to the site using conveying equipment, such as cranes, and are placed.
In cast in situ construction, the concrete casting is done at prefabricated shops which join together with the old concrete surface, and once the concrete is poured, they become inseparable.
Thus bond breaker is used to prevent cracks, which may appear in concrete surfaces due to temperature fluctuations.
- Bond breakers are also used in breaking the bond between substrate and waterproofing membrane system, thus forming an adjustable bridge, resisting the movement of the water or moisture.
- Often a time, the importance of bond breaker as an inseparable part of the waterproofing system is being overlooked.
- If a bond breaker is not applied before the installation of a waterproofing membrane system, there are high chances that the membrane will wear and tear, forming holes, which would allow moisture into the substrate below, rendering the whole purpose of waterproofing system pointless.
- They are also used to resists shrinkage cracks, which may appear on the concrete during casting, due to the unexpected evaporation of water from the concrete surface.
Purpose of Providing Bond Breaker
There is numerous purpose that a bond breaker should be provided on a surface, some of which are:
Dynamic, working, or lifting load is the force that will be applied to the linear actuator while it is in motion.
Static load, also called the holding load, is the force that will be applied to the linear actuator when it is not in motion.
- The primary purpose of providing bond breaker in the surface is to reduce the dynamic loads acting on when the member is lifted. There are two types of loads which generally works in concrete member(based upon nature) Static and Dynamic loads.
Static loads are which, who’s value is constant, and the amount of the dynamic loads, continually changes. Wind loads which act on lifting a precast member, are an example of dynamic loads.
When bond breakers are applied on a surface it substantially reduces the dynamic loads’ acts on the concrete, and also enables stripping of concrete members and permits their clean separation from casting slabs or moulds.
- Many a time, while casting a concrete member, in prefabricating shops, cracks may appear due to the temperature and moisture fluctuations, depending upon the atmospheric condition.
This cracks may take from as simple hair cracks, which with time, propagates, eventually leading to failure of the concrete member. When bond breakers are applied to the concrete surface, it eventually joins together with the old concrete surface and once the concrete is poured, they become inseparable.
Thus bond breaker is used to prevent cracks, which may appear in concrete surfaces due to temperature fluctuations.
- Bond breakers are also used in breaking the bond between substrate and waterproofing membrane system, thus forming an adjustable bridge, resisting the movement of the water or moisture. Often a time, the importance of bond breaker as an inseparable part of the waterproofing systemise being overlooked.
If a bond breaker is not applied before the installation of a waterproofing membrane system, there are high chances that the membrane will wear and tear, forming holes, which would allow moisture into the substrate below, rendering the whole purpose of waterproofing system pointless.
- They are also used to resists shrinkage cracks, which may appear on the concrete during casting, due to the unexpected evaporation of water from the concrete surface.
Materials Used in Bond Breaker
In the modern construction industry, as the technology upgraded, a wide variety of bond breaker materials have been introduced. Bonds breaker materials are generally classified into several forms, they are
- Liquid.
- Spray.
- Rods.
- Tape.
#1. Liquid-
Liquid bond breakers are widely used nowadays as a significant bond breaker materials. In some countries, petroleum-based materials have been in use. Still, these chemicals also dramatically affect the characteristics of the concrete members, so this compound is not known in all countries.
#2. Spray-
Not very much in use. Liquid bond breakers are preferred over bond breakers in spray form.
#3. Rods-
Many a time, rods with a coating of certain chemical compounds, wife mesh, have been used as a bond breaker. Not very much in use in the modern construction industry, due to the lack of professional knowledge and lack of evaluation of side effects.
#4. Tape-
They are also used widely. I have covered this topic, under “what is bond breaker tape “portion in the following. Wax is also a popular bond breaker material which is being used by many countries. Although the use of it includes certain drawbacks, it is still popular as a significant bond breaker material.
What Is Concrete Bond Breaker?
- A bond breaker is a substance applied to concrete surfaces to guarantee that there is permanent bonding between the surfaces.
- Bond breakers are normally used on tilt-up walls and precast segments to ensure the right pieces are cast together.
Types of Concrete Bond Breaker
The bond breakers can be broadly classified into two categories, such as
- Membrane-Forming Bond Breaker.
- Non-Membrane Forming Bond Breaker.
1. Membrane-Forming Bond Breaker
This type of bond breaker holds water into the casting slab. Whenever a casting of the slab is done, it requires an adequate quantity of water, so that the chemical reaction between cement and water can progress uninterruptedly. Many time, due to evaporation and due to different atmospheric condition, there is a lack of water.
To prevent that for precast slabs, membrane-forming bond breakers are applied so that it can hold up the water, necessary for the chemical reaction. This type of bond breakers is made of crude resins.
2. Non-Membrane Forming Bond Breaker
This type of bond breaker is opposite to that of the previous one. This type of bond breaker does not form a membrane which can hold up the water.
Non-membrane forming bond breakers are sub-divided into two categories
- Reactive.
- Non Reactive.
#2.1. Reactive-
This type of bond breaker will react with water and form a crude soap
#2.2. Non-Reactive-
This type of bond breaker will interact with the concrete surface and will create a waterproof film.
What is Bond Breaker Tape?
Bond breaker tape is self-adhesive polyutherene tape, having black colour, which has comfortability hugely to irregular surfaces. Bond breaker tapes are used for isolating sealant and eliminating sealant adhesion to concrete and metal. Bond breaker tape stops the sealant from adhering to the surfaces and prevents the three-sided adhesion.
To prevent the sealant from adhering to the surfaces, bond breaker tape is applied along the whole width/length of the base of the joint. Bond breaker tapes are available in following width:15mm, 20mm, 25mm, 50mm.
Advantages of Concrete Bond Breaker
- Bond breaker tape reduces the amount of time to move loads. As the dynamic loads are substantially decreased, it takes less time as well as less effort to carry a heavy load from one point to another.
- Bond breaker can be reused multiple times, which makes it a very cost-effective material for precast elements.
- It preserves the characteristics of the concrete surface, allowing them to painted or modified using different architectural components, thus making the precast elects, visually appealing.
- Bond breaker does not affect the adhesion of epoxy (if applied), adhesive, and floor finishes.
Bonding Concrete to Existing Concrete
- A bond breaker literally breaks the bond between the substrate and waterproofing membrane to create an elastic ‘bridge’ that can stretch as buildings flex and move.
- The bond breaker is applied in joints where walls meet floors or two walls meet in a corner. They are also used over movement joints.
FAQ: Bond Breakers in Modern Construction
What Is a Bond Breaker?
A bond breaker is a substance applied to concrete surfaces to prevent cracks and ensure that concrete elements do not bond with each other during the curing process. This is essential in both precast and cast-in-situ construction to maintain the integrity and separability of concrete elements.
Why Are Bond Breakers Important in Construction?
Bond breakers are crucial because they prevent cracks due to temperature fluctuations and reduce dynamic loads acting on concrete members during lifting. They also ensure clean separation of concrete elements from casting slabs or molds, preserving the quality of the concrete surface.
What Are the Different Types of Bond Breakers?
Bond breakers can be broadly classified into two categories:
- Membrane-Forming Bond Breaker: Holds water in the casting slab, essential for the chemical reaction between cement and water.
- Non-Membrane Forming Bond Breaker: Does not form a membrane to hold water and can be further subdivided into reactive and non-reactive types.
What Materials Are Used in Bond Breakers?
Bond breakers come in various forms, including:
- Liquid: Widely used, though petroleum-based materials may affect concrete characteristics.
- Spray: Less commonly used compared to liquid bond breakers.
- Rods: Coated with chemical compounds, though not widely used due to lack of professional knowledge and evaluation of side effects.
- Tape: Self-adhesive polyurethane tape used to isolate sealant and prevent three-sided adhesion.
How Does a Membrane-Forming Bond Breaker Work?
A membrane-forming bond breaker retains water in the casting slab, ensuring the chemical reaction between cement and water progresses uninterruptedly, preventing water loss due to evaporation.
What Is the Difference Between Reactive and Non-Reactive Non-Membrane Forming Bond Breakers?
- Reactive Bond Breakers: React with water to form a crude soap.
- Non-Reactive Bond Breakers: Interact with the concrete surface to create a waterproof film.
What Is Bond Breaker Tape, and How Is It Used?
Bond breaker tape is a self-adhesive polyurethane tape used to isolate sealant and prevent adhesion to concrete and metal surfaces. It is applied along the width/length of the base of the joint to prevent three-sided adhesion.
What Are the Advantages of Using Concrete Bond Breakers?
- Reduce the amount of time and effort needed to move loads.
- Can be reused multiple times, making them cost-effective.
- Preserve the characteristics of the concrete surface, allowing for painting or other modifications.
- Do not affect the adhesion of epoxy, adhesive, or floor finishes.
Can Bond Breakers Be Used in Waterproofing Systems?
Yes, bond breakers are used in waterproofing systems to break the bond between the substrate and the waterproofing membrane, creating an elastic bridge that resists water or moisture movement and prevents wear and tear on the membrane.
How Do Bond Breakers Help in Bonding New Concrete to Existing Concrete?
Bond breakers ensure that new concrete does not bond permanently with existing concrete, allowing for flexibility and movement, which is essential in joints where walls meet floors or two walls meet in a corner.
