Bonded anchors – properties and application in extreme conditions
Bonded anchors are versatile fixing solutions that prove perfect for both professional applications as well as less demanding renovation jobs. The strength and reliability of bonded anchors make them suitable for use also in extreme conditions. What conditions are they? Read on to find out.
Weather conditions are inextricably linked with the planning process under each construction or installation project, often turning from a mild challenge into a real nightmare facing engineers and contractors. Decisions concerning the choice of fixing techniques and materials for a variety of substrates must take into account the potential extremes, from cold winters to hot summers, from dry spells to rainy periods. However, it is not just the variable weather conditions that can present difficulties to anyone choosing adequate fixing techniques. The installation conditions themselves – irrespective of the weather – often qualify as extreme and require highly specialised approach and solutions.
Choosing the right bonded anchor – what to consider?
This choice depends on the dynamic loads encountered in busy public areas, the exposure to aggressive chemicals in industrial production facilities, or any special requirements of high-precision engineering structures – all these challenges require not only thorough understanding of the nature of each task, but also in-depth knowledge of the available fixing technologies. In this light, bonded anchors appear to be among the most flexible, yet robust solutions.
Types and applications of bonded anchors
In contemporary construction industry, innovative fixing methods play an increasingly important role, and they are assumed to meet growing requirements in terms of both strength and performance. Bonded anchors are among the most crucial solutions applied in this area, especially when it comes to installation of rebars and threaded rods in concrete, but also in other construction materials (e.g. masonry), as in the case of polyester anchors. The choice of an adequate bonded anchor is of considerable importance to the durability and stability of structures.
If you wish to choose the anchor properly, you first need to understand the specifications of a given product. Analysing the conditions under which the anchor is to be used should help in choosing the right resin, so as to avoid any potential mistakes. However, it is important to remember that in order to use such techniques for fixing, one must not only prepare the substrate appropriately, but also execute the application correctly.
Regardless of the type, bonded anchors can be applied close to the substrate edge, thus minimising the risk of edge damage, which is possible since no stress is generated in the material during installation. Therefore, chemical fixings of this type are ideal for the installation of such elements as bridge deck overhangs, motorway barriers, or high-bay shelving.
You can find more information on the minimum edge distance of the anchors installed in concrete in this post.
However, it is important to keep in mind that there are different types of bonded anchors, which is why one should carefully consider their advantages and disadvantages before choosing the right one. Some of the fundamental questions that need to be answered before buying a specific product concern the place where and the time when the anchor is to be applied, but these are not the only ones.
Fixing with Rawlplug’s bonded anchors is conducted using the following application solutions:
- cartridge system,
- cartridge free system (CFS+), which reduces waste and requires a special squeezer,
- and capsule system – perfect for single anchoring jobs and requiring no dedicated tools.
Bonded anchor application
A bonded anchor is actually not only the resin, but also the element being anchored:
- a threaded rod,
- a reinforcement bar, or
- an internally threaded socket.
You should not use elements made of steel of a grade below 5.8. Grade 8.8 materials are also often used for additional strength.
What also matters a lot is the precision of the drilled hole. For studs of sizes:
- from 8 to 16 mm, the hole should be 2 sizes larger,
- from 20 to 24 mm – 4 sizes larger,
- above 30 mm, the hole diameter should be as much as 5 mm larger.
An equally important aspect to remember is adequate hole cleaning, since it has a direct impact on the load capacity of bonded anchors. When fixing in substrates other than concrete (e.g. in hollow materials), it is essential to use a mesh sleeve to prevent resin spillage inside the hollow block, thus ensuring anchorage stability and durability.
Also, you must not ignore the importance of the information provided on the product label, including:
- expiration date,
- installation time – the period of time during which the rod must be embedded in the hole,
- setting time – the time after the lapse of which the anchor can be loaded,
- and substrate temperature, which has a significant impact on the resin setting process.
Understanding and following these principles is essential not only to the anchoring effectiveness, but also affects the durability and security of fixing in extreme conditions, making bonded anchors indispensable for a wide range of construction and installation jobs.
Which bonded anchor to choose? Types of resin for concrete applications
The substrate type, the right amount of resin compound, the method of use, the compound application, the load and fixture type, or the hole, properly drilled and cleaned, are just some of the factors that need to be taken into account when planning work which involves using bonded anchors. This is precisely why, when choosing the right resin for the job, it is so important to consider not only the advantages and disadvantages of a given product, but also the specificity of the environment in which the anchor is to be applied.
There are actually several classifications of bonded anchors, but most frequently, they are simply broken down according to the base material. After all, all of them are suitable for concrete. However, the polyester bonded anchor is the only one that can be used in hollow substrates (e.g. when fixing in hollow masonry units).
Epoxy bonded anchor
Epoxy resin displays the highest performance in terms of strength and reliability. It is characterised by a slow curing process, while forming an incredibly strong bond with concrete substrates, ensuring durability that lasts for years. Its unique composition, based on epoxy prepolymers combined with selected hardening agents, makes it possible to attain unparalleled mechanical and chemical strength parameters. This makes it the solution of choice for jobs that require not only stability but also prolonged resistance to operating conditions, such as anchoring of heavy steel structures or industrial machinery, where reliability is prerequisite of safety.
Hybrid bonded anchor
In projects which require operating speed without any compromise on strength, hybrid bonded anchors appear to be the optimal solution to any challenges. Combining speed of curing with reliability similar to that of epoxy resins, they seem to be the perfect choice for those who seek installation efficiency while maintaining structural strength. They prove particularly valuable when it comes to installation of elements that require immediate fixing, such as poles or beams, where every second of work makes a difference.
Vinyl ester bonded anchor
As an alternative to traditional application methods, vinyl ester resins in capsules represent a highly practical and economical solution for single fixing jobs. They stand out with their improved technical properties, very good resistance to moisture, and capacity to withstand extreme temperatures. This is an excellent choice for professional applications, including installation of balustrades, guard rails, or storage racks.
Polyester bonded anchor
Developed with versatility in mind, polyester resin anchors are perfectly suitable for a wide range of substrates, from conventional concrete to masonry materials, representing one of the most flexible solutions. In the case of hollow substrates, a special mesh sleeve is required for their application, preventing the resin from spreading in porous structures. Such innovations extend the scope of their potential use, making them fit not only for industry, but also for home applications, such as the installation of facade systems, wall brackets, awnings, or garage doors.
In order to optimise the process of resin selection for the job at hand, using dedicated software, such as the EasyFix program is definitely worth your while. It allows you to define input anchoring parameters in great detail, taking the substrate and load type or the edge distance into account, which proves an invaluable aid while planning effective and secure fixings.
An entry dedicated to calculating the amount of resin needed for installation can already be found on our blog!
Advantages of bonded anchors. Extreme fixing conditions.
When discussing advanced installation techniques, the term extreme conditions receives a special meaning, as it refers to a broad range of extremely problematic circumstances that can occur during the application and operation of bonded anchors.
- Extreme temperatures. Temperatures so low that they can slow down the chemical reactions necessary for resins to set, or so high that they can accelerate this process, often to unwanted consequences, require a special approach to the selection and application of bonding materials.
- Humidity and water flooding. They represent yet another challenge, especially in environments exposed to continuous impact of water or high humidity, where adhesion and corrosion control is absolutely crucial.
- Aggressive chemical environment. The term aggressive chemical environment is typically used with reference to places where substances such as salts, acids, alkalis, or organic solvents are present in high concentrations, which can lead to corrosion, degradation, or even destruction of structural materials.
- Dynamic loads and vibrations. Dynamic loads and vibrations, such as those which occur in areas of heavy vehicle traffic, near operating machinery, or in structures exposed to regular impact forces, represent unique challenges for bonded anchors. What matters under such conditions is not only adequate anchorage, but also the anchor’s capacity to absorb and dissipate energy.
- Extreme pressures and loads. In engineering and construction applications, where anchors are subject to extreme pressures and loads, for instance in bridges, high rise buildings, tunnels, or dams, compressive, tensile, and shear strength becomes absolutely critical. When properly selected, anchors can not only maintain the structure integrity under normal operating conditions, but also withstand the additional forces caused by disastrous natural phenomena, such as earthquakes, hurricanes, or floods.
Where are epoxy anchors used?
Seismic zones
In regions prone to seismic activity, the engineering and construction of built features require taking the potential forces induced by earthquakes into consideration. Given such a context, using bonded anchors intended for concrete seems to be the most reasonable decision. Owing to the capacity to form flexible yet strong bonds between structural elements and the substrate, bonded anchors prove invaluable when it comes to protecting structures against damage caused by seismic tremors.
The innovations introduced in the field of chemical anchoring focus on enhancing the capacity of fixings to absorb energy and dissipate stresses, which is essential in seismic conditions. Special resin formulations are developed to maintain structural integrity even during intense tremors. Furthermore, chemical anchoring plays an important role not only in new constructions, but also in the processes of retrofitting and reinforcement of existing structures.
When the ground trembles and buildings are exposed to extreme trials of strength, epoxy resin anchors become indispensable in securing the stability of structures. With their exceptional flexibility and capacity to absorb vibrations, these highly specialised resins are often chosen for applications in earthquake-prone regions. Designed to withstand extreme loads, epoxy anchors maintain structural integrity, reducing the risk of damage due to dynamic seismic forces. Their unmatched potential for adhesion to concrete and steel, proven in numerous tests and practical applications, provides the foundation of safety under unpredictable natural conditions.
Epoxy anchors and fire resistance
With regard to fire safety, the choice of anchoring systems that will retain their structural properties even when exposed to extreme temperatures generated by fire is fundamental. Although essentially non-flammable, bonded anchors are subject to degradation under the impact of high temperatures, which requires special attention when it comes to their selection and application in construction projects.
What is meant by the fire resistance of bonded anchors is their ability to retain structural integrity and load capacity during a fire. The adhesion strength of the bonds formed by chemical agents deteriorates rapidly at high temperatures, for instance in cases of fire. For this reason, the anchor may become no longer capable of holding stationary objects in place, thus posing a life-threatening hazard.
In a fire scenario, where every second determines consequences, epoxy anchors stand out as a fire-resistant solution that can provide additional time for evacuation as well as for response of emergency services. Having improved resistance to high temperatures among their characteristics, epoxy resins retain their mechanical properties even when exposed to intense heat. This type of chemical anchor creates strong and heat-resistant bonds, as confirmed in numerous studies and tests.
Bonded anchors and corrosion resistance
Galvanic and atmospheric corrosion
When choosing connecting pieces for the job at hand, corrosion resistance plays a major role. In this respect, one may speak of two kinds of corrosion: atmospheric and galvanic.
- Galvanic corrosion occurs at the point of contact between two different metals, leading to the formation of a galvanic cell, which results in gradual deterioration of one of these metals.
- Atmospheric corrosion, on the other hand, results from the impact of the air and the chemicals it contains on metal, and its intensity depends on both the concentration of these substances and the humidity of the environment.
Being an organic material, resin itself is not subject to corrosion in the way we understand this process in the context of metals. The resins used in bonded anchors are resistant to corrosion, because they do not react chemically with water or oxygen in a manner that would lead to their degradation, which is the case of metal components. When considered in the context of chemical anchoring systems, the problem of corrosion concerns rather the metal elements fixed, such as rebars or threaded rods, or any other structural reinforcements embedded in the substrate using resins.
Even though the resin itself is corrosion resistant, the use of adequate measures of protection proves crucial to the metal components being anchored. These may include choosing corrosion-resistant metals, or application of protective coatings or galvanic protection that will secure the metal against corrosion in potentially harmful environments.
In places exposed to aggressive chemicals, the choice of an anchor capable of protecting metal components from corrosion is essential. Vinyl ester anchors have proved to perform well under such conditions, providing not only high-strength bonding, but also forming a protective coat around metal components. Their application in industrial facilities, including chemical and sewage treatment plants, makes it possible to safeguard metal against the effects of corrosion, even in the case of direct exposure to chemicals.
Related articles
25 September 2024
#PortfolioRawlplugRawlplug delivered solutions to a global leader in the construction of cooling towers!
20 September 2024
#PortfolioRawlplugRawlplug supports the expansion of a pioneering healthcare facility in Vietnam!
11 September 2024
#PortfolioRawlplugRawlplug products transforming the marina: the modernization of Puck port
14 June 2024
#Bonded anchorHow bonded anchors work – a practical guide