Construction Fixings

Here Metehan Ariburnu, international technical support engineer for construction projects at fischer, discusses the development of chemical anchors and how they have become a key solution for applications within the construction sector.

When did fischer introduce its range of chemical anchors and how has the range’s capabilities and features developed during this time?

“fischer’s range of chemical anchors all began in 1975 with the invention of the FI M Injection System. Since then, the product line has grown significantly with a structured strategy through investments in R&D – focused on new products and market requirements.

The real big development in fischer’s range of chemical anchor solutions came in 1999 when the company inaugurated a new plant for chemical products in Denzlingen, Germany. This enabled the company to develop its range of solutions and further meet the growing needs within the market for ‘more strength in more extreme conditions’ – including dynamic applications.

Historically, there had been a lot of standard chemical anchor solutions for static loading – where there is a continuous pull/force on the anchor. However, in dynamic loading the force on the anchor can shift back and forth from nothing to very high. The requests from customers regarding chemical anchors that could meet the dynamic loading requirements were increasing and through our R&D development we were able to introduce various new lines of chemical anchors, which met not only customers’ needs but the standards as they have developed.

Thanks to the experience and knowledge within the business, fischer has introduced numerous new products over the last 22 years. This includes dynamic capsules in 1999, hybrid resins and vinylester resins in 2002, pure epoxy resin mortars – launched in 2004, followed by polyester resins for temporary applications. To add to this there was the new generation of hybrid materials – such as Superbond – which were launched in 2012 and made available in cartridge and capsule form.

In 2014 we introduced the GREEN line, which is completely environmentally friendly. We have also continued to work on improving the product resistance, especially for vinylester and epoxy, which has seen us introduce enhanced products such as our main FIS EM and FIS EM Plus.

At fischer we are always looking to meet the needs of our customers and finding the answers to their applications. We have shown this throughout the history of the company and we have even more new products planned for 2021 and beyond.”

How has the growth of fischer’s chemical anchor range been impacted by the construction market and applications?

“I would argue that it is a mix of the construction market impacting the development of products and the products themselves impacting the types of applications within the market. As chemical compounds have improved the different applications in which they can be used has risen. For instance, in the 1960s – 1970s, polyester resins were really popular, but structurally the polyester was not strong enough to reach the required performance. Once the new generation of resins were introduced, and showed their potential, end users started to focus on the possibilities.

The growth in chemical anchors has created more opportunities for end users who have in turn brought new application ideas to the table – covering a large range of construction fields in both superstructures and infrastructures, especially where high capacities are required. The reason for this is the high bonding strength of chemical anchors creates a major advantage in terms of load capacities with higher demands.

This means chemical anchors can be used in a wide range of construction types such as high rise buildings, railways, stations, highways, as well as power plants.”

How do chemical anchors and mechanical anchors compare to each other? What are the pros and cons of each?

“The behaviour of chemical and mechanical anchors differs slightly between the two. Mechanical anchors provide friction inside the concrete for a defined area – where all the loads are applied. In chemical anchors, there is a full length bond all along the hole inside the concrete. This means chemical anchors are more flexible in terms of selecting the embedment depth and the more embedment depth you have, the more load capacity up to a certain defined point for each size.

For instance, if we compare M12 single anchors, without having an edge distance inside C20 concrete, the difference between the concrete failure modes under tension is 15% with an equal embedment depth of 70mm. However, in this case, 70mm is the upper limit of the mechanical anchor whereas it is the lowest limit of the chemical anchor. It is possible to increase the embedment depth of the chemical anchor up to 240mm, in which case the difference is 75%. This means chemical anchors can cover all applications according to every condition.

Having said that, whilst the first mechanical anchors could only be used at a set predefined anchoring depth, there are mechanical anchors that are now available that permit multiple or even flexible anchoring depths. This primarily applies to bolt anchors and concrete screws.

Another major advantage of chemical anchor systems is that there is no expanding force when placing the anchors. Whilst all systems generate expanding force when they are subjected to loads, with chemical anchor systems this expanding force is lower and as the load is transferred into the construction base it is distributed across a larger area – due to the large bonded length.

One of the disadvantages of chemical anchor systems is that the durability is reduced in case of heavy constant tensile load. A reduction factor was therefore introduced for calculations, which means that the difference between the mechanical anchor’s tensile load is slightly smaller, even under similar edge conditions. Higher requirements also apply when it comes to cleaning the drill hole, although significant progress has been made in recent years. Chemical systems also tend to be more expensive and require additional annular gap filling measures when applying push-through installation methods. Capsule systems can therefore often only use pre-positioned methods of installation.”

What are the key factors a customer should consider when deciding whether to use a mechanical or chemical anchor?

“There are several factors users should consider to help them make the correct decision. What is the condition of the application (structural or non-structural)?; what is the application media – concrete, masonry, etc?; as well as what is the layout of the application?

The load conditions are the next point – static, seismic or dynamic – and the user needs to consider fire conditions, etc. For instance, for static and seismic both mechanical and chemical anchors can be used, but when it comes to dynamic loads, chemical anchors are a better option. In fire applications both mechanical and chemical anchors can again both be used. At fischer we have even developed enhanced chemical products that provide good performance under fire and are very close to mechanical anchors’ capabilities.

After the applications and loads, the user needs to check the application method and difficulties at the construction site – which involves things such as temperature, application position, etc. For instance, temperature, whether extremely hot or cold, has a big impact on the resin type when choosing a chemical anchor.

The last factor to consider is the economic efficiency. Is it worth it? Chemical anchors require more cleaning, as not cleaning the holes can significantly impact the load bearing capacity, which can be time consuming. However, chemical anchors can be pre-positioned, which makes installation easier.

Even if a user has made all of these decisions, there is still a whole range of solutions that could still be used. On the fischer website alone we have thousands of products for different materials and applications. Customers are not going to know the details of all those products, but we do, which is why we look to work alongside users and engineers. This means we can check the design loads, the technical specifications, and boundary conditions, as well as all the other requirements, so we can supply the simplest solution that optimises the design.”

What do you see as being the big trends for chemical anchors in the future? How can fischer benefit from these opportunities?

“The requirements of the market and boundary conditions, as the limits are pushed by designers due to extreme demands, will continue to be a big trend within the market and is always pushing us to provide products with a higher performance than we have at that moment.

Digitalisation is also coming and will be an important step for where the construction market goes. Right now, we are offering customers innovative digital services and digital start-ups – while creating new operating principles in construction and providing smart products with the principles of a Lean company. The world is changing and turning into a faster, more digitalised world and the brands that can adapt to this new world will remain standing.

Here at fischer, our advantage is that we are always leading the market, be it with innovative products and ideas; following the requirements of the changing world; or by creating modern trends and know-how – with new ideas developed by our fischer ProcessSystem. This was developed by fischer to increase efficiency and creativity in line with society, ecology, and economy, to achieve sustainability, which we refer to as the ‘Blue Path’.

By focusing on both digitalisation and following our ‘Blue Path’, as well as continuing to create added value, I believe fischer will remain a market leader.”