Bitumen mastic has been proven to be a highly effective material for waterproofing applications on various surfaces, such as flat and sloped roofs, as well as tanks. One of the key advantages of bitumen mastic is its fluidity at processing temperatures, allowing it to be easily applied to form a dense and continuous layer without the need for compacting. This makes it suitable for covering flat, sloped, or curved surfaces, providing a seamless waterproofing solution.
Another notable characteristic of mastic asphalt is its excellent deformation capacity, which enables it to resist cracking even at low temperatures. This makes it highly durable and reliable, particularly in areas where temperature fluctuations are common. The strong cracking resistance of mastic asphalt ensures that it maintains its integrity and effectiveness as a waterproofing material, providing long-lasting protection against water infiltration.
Overall, bitumen mastic has emerged as a successful choice for waterproofing treatment due to its fluidity, ease of application on various surfaces, and superior cracking resistance at low temperatures. Its properties make it a reliable option for a wide range of applications, including flat and sloped roofs, as well as tanks, providing effective and durable waterproofing solutions.
Fig 1: Bitumen Mastic Waterproofing
Bitumen mastic is commonly used as a waterproofing treatment, and several factors such as thickness, remelting, and laying methods need to be considered for its effective application.
Firstly, the thickness of the bitumen mastic layer is crucial for ensuring proper waterproofing. The recommended thickness of the layer depends on various factors such as the type of surface, the severity of the waterproofing requirement, and the specific application. Generally, a thicker layer of bitumen mastic provides better waterproofing performance, but it also requires more material and may increase the overall cost of the project. Therefore, it is essential to carefully determine the appropriate thickness based on the specific requirements of the project.
Secondly, remelting of the bitumen mastic is an important consideration during the application process. Bitumen mastic typically needs to be heated to a certain temperature to achieve proper melting and flow characteristics for effective application. The remelting process can be carried out using various methods such as hot air guns, torches, or heat lamps. It is crucial to follow the manufacturer’s recommendations and guidelines for remelting to ensure that the bitumen mastic is properly heated to the required temperature for optimal performance.
Finally, the method of laying the bitumen mastic is also critical for achieving effective waterproofing. The specific method of laying can vary depending on the surface and application requirements. Common methods include brush or trowel application, spraying, or using a roller. It is important to follow the recommended laying method as per the manufacturer’s instructions to ensure proper coverage and adhesion of the bitumen mastic.
In conclusion, when applying bitumen mastic for waterproofing treatment, the thickness of the layer, remelting process, and laying method are important factors to consider for ensuring optimal performance. Careful attention to these factors will result in a successful and effective application of bitumen mastic for waterproofing purposes.
Thickness of Bitumen Mastic
The bitumen mastic is required to be applied to all types of surfaces, whether they are sloping, horizontal, or vertical, and in either one or three coats. The thickness of the bitumen mastic must be in accordance with the following specifications.
For walls and floors located above ground level, a single coat of 10mm bitumen mastic shall be applied.
However, for surfaces that are vertical or steeper than 30 degrees, the bitumen mastic shall be applied in three coats. The total thickness of these three coats should be less than 20mm.
For horizontal surfaces and sloping surfaces that are not steeper than 30 degrees, the bitumen mastic must also be applied in three coats. The total thickness of these three coats should not exceed 30mm.
Remelting of Bitumen Mastic
The process of remelting the bitumen mastic blocks shall take place on site in a mechanical mixer. To ensure that the mastic does not overheat, the temperature should not exceed 200 degrees Celsius during the remelting process. The mastic blocks shall be broken down into pieces and then arranged in layers around the sides of the mixer before moving inwards towards the center.
The mastic shall be heated gradually until it reaches a temperature of approximately 200 degrees Celsius. Once the mastic reaches a molten state, it must be continuously agitated to ensure a consistent and uniform texture. The heating duration should be carefully determined to prevent any damage to the properties of the bitumen.
Method of Laying Bitumen Mastic
The three-coat treatment method for applying bitumen mastic involves the initial application of a thin layer of the substance as an adhesive layer to prevent blowing. This layer is applied thinly to any surface. When applying the bitumen mastic on a horizontal surface, each coat is evenly spread with a float over the previously prepared surface. For vertical surfaces, the first coat can be evenly and uniformly applied with a metal trowel. The second and third coats should be applied with a wooden float to achieve a uniform thickness. It is important to apply the bitumen mastic coats quickly to avoid dust or dirt accumulation between layers.
Any blows that may be formed by entrapped air or moisture during the laying of each coat should be punctured and repaired while the asphalt is warm, before the next coat is applied. In the case of chases, the top of the vertical mastic should be turned into a chase in the wall that is no less than 25 mm x 25 mm in size, unless it is being continued horizontally. For fillet cases, an angle fillet that is no less than 50 mm wide should be applied in two coats at two planes forming an internal angle.
When dealing with construction joints, the edges of the previously laid mastic should be warmed with hot asphalt and then cut out with a metal trowel to remove any dust or dirt that may have collected. The fresh mastic should then be poured before the warmed up surface of the joint cools off.
Water-proofing above Ground Level
The above-ground waterproofing treatment must cover the entire thickness of walls, excluding plaster or the base of cavity walls. This means that the treatment should be applied to the entire outer surface of the wall to prevent water from penetrating into the building. It is essential to ensure that the waterproofing is continuous and uniform to prevent any weak points where water can seep through.
Furthermore, the damp proofing within the wall must be linked and continuous with the layer of bitumen mastic on adjacent floors. This will ensure that there are no gaps where water can seep through, and the building remains protected from moisture. It is crucial to maintain the continuity of the damp proofing layer to prevent any water infiltration into the building.
In cases where it is necessary, a vertical damp-proofing course must be installed on the inner surface of the wall. The purpose of this vertical damp-proofing course is to prevent any moisture that may seep through the walls from reaching the interior of the building. This is especially important in areas where the ground level is high or where there is a lot of moisture in the air. The vertical damp-proofing course must be installed according to the specifications in figure 2 to ensure its effectiveness in preventing moisture infiltration.
Water-proofing in External Tanking
When applying external tanking to a structure, it is important to ensure that there is enough working space outside the walls. This space should not be less than 0.6 m in order to allow for proper installation. Additionally, the base concrete of the structure must be at least 100 mm thick and be structurally sound. It should also extend at least 150 mm beyond the edges of the wall to allow for the formation of an angle fillet at the junction of the horizontal and vertical damp-proofing.
Once the layer of mastic asphalt has been applied to the structure, it is crucial to protect it from damage. This can be done by covering it with a 50 mm thick screed of cement and sand. The horizontal coat of the structural slab should also be laid as quickly as possible to ensure that the structure is properly sealed.
After the vertical damp-proofing bitumen mastic is applied to the structure, the outside of the wall must be protected against damage. This can be achieved by erecting a brick wall around the structure. By following these guidelines, the external tanking of a structure can be completed effectively and efficiently.
Water-proofing in Internal Tanking
Before applying bitumen mastic, it is important to take certain precautions. Firstly, a space of 300mm outside the wall should be provided during excavation in order to keep the wall dry while laying the bitumen mastic.
Secondly, the base slab must be given an even surface and the walls should be built to the required height before commencing the laying of the mastic asphalt.
Thirdly, backfilling of the earth should not be allowed until three coats of vertical mastic are applied and the loading coat is hardened, as shown in figure 4. This is necessary for proper adhesion and to prevent any damage to the mastic.
Fourthly, as in external tanking, protective layers of screed should be laid before the structural floors and walls are laid. This ensures that the mastic remains protected and provides a sturdy foundation for the structure.
Overall, taking these precautions is important to ensure the effective application and longevity of the bitumen mastic.
FAQs
What is the thickness of bitumen mastic applied for different uses?
The application of bitumen mastic is required on all surfaces, whether they are sloping, horizontal, or vertical. The thickness of the bitumen mastic shall vary depending on the surface being coated and the number of coats applied.
For walls and floors above ground level, a single coat of 10mm bitumen mastic shall be applied. However, for vertical surfaces and surfaces with a slope greater than 30 degrees, the bitumen mastic shall be applied in three coats, with a total thickness of less than 20mm. Similarly, for horizontal surfaces and surfaces with a slope less than or equal to 30 degrees, the bitumen mastic shall be applied in three coats, with a total thickness of less than 30mm.
It is essential to ensure that the correct number of coats and thickness of bitumen mastic is applied to each surface. Failure to do so may result in suboptimal performance and potential damage to the coated surface. Therefore, it is imperative to follow the application guidelines provided for each surface type to ensure adequate protection and longevity of the coated surface.
How to remelt bitumen mastic for waterproofing?
The remelting process should take place on-site using a mechanical mixer, ensuring that the mastic temperature does not exceed 200 degrees Celsius. The bitumen mastic blocks should be broken into smaller pieces and stored in layers, starting from the sides of the mixer and moving towards the center. Gradual heating of the mastic should be carried out until it reaches around 200 degrees Celsius. Once the mastic is in a molten state, continuous agitation is required to maintain a uniform consistency. The duration of heating should be carefully determined to avoid any impairment of the properties of the bitumen.