Concrete spalling is a phenomenon where the surface of the concrete breaks away, often revealing the top layers of reinforcing steel. This can result in a patchy and pitted appearance while also exposing the aggregate underneath. If left unaddressed, spalling has the potential to compromise the integrity of the concrete element and can impact the ultimate capacity of the member. Therefore, it is important to repair spalling as soon as it is detected.
When it comes to repairing concrete spalling, the specific technique to be used will depend on a few factors. These factors include the severity of the damage, the type of concrete structure involved, and its location. To ensure that repairs are carried out safely and effectively, it is important to follow the recommendations provided by relevant codes such as the ACI Code and BS EN 1504.
Following these guidelines will help to ensure that the repair technique adopted is appropriate for the situation at hand. It will also help to ensure that the repair is carried out in a way that is consistent with established standards and best practices. Ultimately, this will help to ensure that the repaired concrete structure is safe, durable, and able to withstand the stresses and strains that it is likely to encounter over time.
Material Specification
In order to ensure the proper repair of spalled concrete, it is necessary to use epoxy resins that meet certain standard requirements. These requirements are outlined in a table, and it is important to adhere to them in order to achieve the desired result.
The epoxy resins used in the mortar for the repair of spalled concrete must meet the standard requirements specified in the table. These requirements are considered essential for the proper repair of spalled concrete, and should not be overlooked or ignored.
It is important to understand that using epoxy resins that do not meet the standard requirements can result in a suboptimal repair of spalled concrete. As such, it is highly recommended that only epoxy resins meeting the standard requirements be used for this purpose.
Overall, the standard requirements for epoxy resins used in the mortar for the repair of spalled concrete are an important consideration that should be taken seriously in order to achieve the best possible outcome.
| Properties | Standard Requirement |
| Pot Life | 90 minutes at 25 degrees Celsius 60 minutes at 30 degrees Celsius 45 minutes at 35 degrees Celsius |
| Bond Strength | 12 MPa |
| Tensile Strength | 16 MPa |
Proportioning and Mixing of Epoxy Mortar
Proper mixing is essential when working with resin, hardener, and dry filler to create a high-quality mortar. To achieve optimal results, it is important to follow specific guidelines. Firstly, the resin and hardener should be combined before adding the dry filler. Additionally, it is important to ensure that the mixed mortar is free of lumps and has a uniform color.
When dealing with small quantities, hand mixing is typically sufficient. However, for larger batches weighing more than 1 kg, a jiffy mixer should be used to blend the components at a slow speed (400-600 rpm) for 3 minutes. The stirrer should be moved up and down and along the sides of the container until the mixture is evenly colored without any streaks. It is essential to avoid introducing excessive amounts of air into the mixture.
In situations where no power is available, a flat putty knife can be used to reach into the corners of the can, and hand mixing should be done for at least 5 minutes to ensure that the mixture is thoroughly blended. Overall, by following these guidelines, one can produce a high-quality mortar that is uniform in color and free of lumps.
Surface Preparation of Spalled Concrete
To ensure proper adhesion, it is crucial that the surface where epoxy will be applied is free of any harmful materials such as rust, grease, oil, paint, asphalt, loose material, unsound concrete, dust, or any other contaminants. This is because cured epoxy cannot create a strong bond with any material, which means that all overlay, whether it is epoxy or cement-based, should be done within the pot life of the base epoxy layer.
To prepare the surface, it is necessary to remove any contaminants such as oil, grease, tar, asphalt, paint, wax, curing compounds, or surface impregnates like linseed oil, including laitance and weak or loose concrete. When bonding to asphalt, the surface should be roughened to expose clean aggregate. It is also important to avoid applying epoxy bonding agents during rainy weather or in standing water, and the surface must be dry before application.
There are two general methods of surface preparation: mechanical and chemical. The mechanical method includes using equipment such as grinding, grit blasting, water blasting, and scarification to remove contaminants and provide a suitable surface for bonding. On the other hand, the chemical method involves acid etching using a 15 percent by weight of hydrochloric solution, followed by repeated flushing with a high-pressure stream of water to ensure that the surface is clean and free of any harmful materials.
Applications of Epoxy Mortar
To apply an epoxy primer coat, the surface and extent of the work area should be taken into consideration. Stiff nylon bristle brushes, hard rubber rollers, or spray guns can be used depending on the nature of the surface. The goal is to achieve a uniform thickness for the coating.
After the primer coat is applied, but before it is fully cured, epoxy mortar can be applied using trowels and floats. The interval between the primer coat and epoxy mortar application should be around 15-30 minutes, depending on the ambient temperature.
Once the primer coat and epoxy mortar are applied, a seal coat should be applied. It’s important to wait for 24 hours after mild roughening of the surface of the mortar before applying the seal coat. This will ensure that the surface is properly prepared for the seal coat to be effective.
Coverage of Epoxy Mortar
The coverage area of a resin mix depends on the specific resin system being used. However, there are some general guidelines that can be followed. For example, when applying a primer coat, one kilogram of resin hardener mix can cover an area of 3-6 square meters per coat, depending on the finish of the concrete.
When it comes to applying epoxy mortar, it is typically recommended to use approximately 20-24 kilograms of epoxy mortar per square meter of surface, if laying it to a thickness of 10 millimeters.
Finally, for seal coat application, it is generally recommended to apply the coat over an area of 4 to 6 square meters per kilogram of the resin mix. This coverage area can be affected by the temperature at which the application is being done.
Handling Precautions of Epoxy Mortar
Epoxy resins have the potential to cause skin irritation, especially for individuals with sensitive skin. To prevent skin contact, it is crucial to handle the resin and hardener with care and avoid direct contact with the skin. The most effective way to protect oneself is by wearing protective gear such as rubber or polythene gloves, along with protective clothing like rubber gloves with a cloth liner.
Although barrier creams can be used, they are not a substitute for proper protective clothing. Additionally, it is essential to protect the eyes from splashing while spraying or mixing the materials. Adequate ventilation is necessary to prevent inhalation of vapors. If materials are being sprayed, a respirator must be used.
In case of skin contact with the resin and hardener, the affected area should be immediately washed with a cleaner followed by soap and water. If clothing comes into contact with the materials, it should be changed immediately to prevent further skin contact. If both the components of the epoxy resin come in contact with the clothing, it should be discarded.
Finally, it is important to dispose of all emptied, used buckets, rags, and containers in waste disposal bags and to remove them from the site to avoid any potential hazards.
FAQs
What are the required bond and tensile strength of the epoxy mortar used to repair spalling concrete?
To effectively repair spalling concrete, it is important to use an epoxy mortar with the appropriate bond strength and tensile strength. The required bond strength for this type of repair is 12 MPa, meaning that the epoxy mortar must be able to withstand a certain amount of force without breaking away from the concrete surface. Additionally, the required tensile strength for the epoxy mortar is 16 MPa, which indicates the amount of force the mortar can handle before breaking apart. It is crucial to select an epoxy mortar with the correct specifications in order to ensure a strong and durable repair that will withstand the test of time.
What is the mixing procedure for epoxy mortar used to repair spalling concrete?
When it comes to mixing substances that weigh 1 kg or less, hand mixing will suffice. However, for larger quantities exceeding 1 kg, a different approach is needed. In this case, it is recommended to use a jiffy mixer and mix the components for 3 minutes at a slow speed of 400-600 rpm. This ensures that the substances are mixed thoroughly and evenly, without leaving any lumps or clumps. By following these guidelines, you can achieve the desired consistency and quality of the final product. It is important to note that proper mixing is crucial for ensuring the effectiveness and safety of certain materials, so it is always best to follow the recommended mixing instructions carefully.
What should be the time interval between the application of primer coat and epoxy mortar?
When applying a primer coat followed by an epoxy mortar, it is important to consider the ambient temperature and the appropriate time interval between the two applications. Generally, this interval should be around 15 to 30 minutes, with the exact timing depending on the specific temperature conditions at the time of application.
The primer coat is a preparatory layer that helps to enhance the adhesion and durability of the epoxy mortar. Once the primer coat is applied, it is important to wait the appropriate amount of time before applying the epoxy mortar. This interval allows the primer coat to properly set and dry, creating a stable base for the subsequent layer of epoxy mortar.
The specific timing for the interval between the primer coat and epoxy mortar will depend on the temperature and humidity levels in the surrounding environment. In warmer temperatures, the interval may be closer to 15 minutes, while in cooler temperatures, a longer interval of up to 30 minutes may be necessary. By considering these factors and waiting the appropriate amount of time between applications, the primer coat and epoxy mortar can be effectively applied for optimal results.