Expansion joints:
Movement under control

Expansion joints are components made of rubber and metal, or rubber with incorporated metal. Their main function is to absorb the expansions of highway bridges and any other type of bridge.

If I understand correctly, elastomeric bearings are placed underneath to support the weight, while the expansion joint is usually positioned on top. The purpose of the expansion joint is to accommodate the stretching and shrinking of materials as they expand and contract, filling the resulting gaps.

When a bridge is constructed using prefabricated components, there is typically a gap between them instead of being directly connected. The expansion joint serves to absorb the expansion and also fills the gaps between these structures.

A similar concept can be observed in train tracks, where gaps are intentionally left between sections to allow for the elongation and contraction of the rails. However, expansion joints are not used in this case as the train’s wheels can pass over the gaps without issues.

You have already told us that it serves to fill the gaps, but is it only for bridges or are there other types of expansion joints? And what is their main function?

The main function of an expansion joint is indeed to absorb expansions, fill gaps, and prevent damage to prefabricated concrete elements. There are also other types of expansion joints used in the construction of garages, for example, which serve not only to absorb concrete expansion but also to mitigate the noise generated by the gaps in the structure. Without an expansion joint, passing vehicles can create noise. Therefore, the purpose of an expansion joint in parking structures and buildings is to minimize that noise. So, in addition to bridges, expansion joints are used in parking structures and various other building applications.

Expansion joints come in various types, depending on the movements they need to absorb based on the design of the bridge. Whether the bridge is curved, straight, spans two meters or twenty meters, or the type of viaduct, determines the size of the expansion joint. There are also expansion joints specifically designed for bridges to withstand seismic movements and dampen those types of motions. It’s important to note that expansion joints absorb different movements than elastomeric bearings.

Expansion joints primarily accommodate horizontal movements and horizontal forces, while elastomeric bearings are designed to support vertical forces. There are several models available in different sizes, with varying amounts of steel and rubber components.

In many cases, the selection of the expansion joint is also influenced by the expected traffic load on the bridge. The requirements differ for bridges crossing highways, agricultural roads, or pathways, compared to those spanning heavily trafficked routes like the M30, which experience a high volume of vehicles passing by every minute.

So, the sizing and selection of expansion joints are also determined by the type of traffic the bridges will encounter.

Earlier, you mentioned elastomeric bearings and the materials used. I’m not sure if they are exactly the same as expansion joints.

Expansion joints. They don’t have a European standard like elastomeric bearings do, which means the quality of the expansion joint is determined by the manufacturer. In other words, you can use any rubber that has some resistance. However, we have minimum quality standards in place, so not all rubber types are the same. Natural rubber or neoprene rubber can be used, but they don’t have to withstand or undergo mechanical tests like elastomeric bearings do. The requirements for expansion joints are much lower, and the expected lifespan is typically two years, which is significantly different from elastomeric bearings.

As you mentioned, elastomeric bearings have more stringent requirements for manufacturing, such as a lifespan of 100 years, whereas expansion joints have less demanding criteria. However, being manufacturers, you can provide better warranty and durability for the expansion joints because you are accustomed to producing products that last much longer than what expansion joints typically require. I assume you can offer this at a comparable cost to your competitors.

One of our key priorities is quality in our product. In fact, we have gained recognition for our product’s quality in the market, surpassing our competitors. Naturally, we want to make sales, but not at any cost. We aim to sell at a fair price while delivering the most appropriate quality for the product. In fact, if a customer’s expansion joint lasts 20 years instead of five, it’s better for them. Our main focus is providing the best service to the customer, and we believe that the longer our product lasts for the customer, the more satisfied they will be. That’s the guiding philosophy of our company.

Indeed, a customer who buys an expansion joint expecting it to last five years but ends up with a product that lasts 20 years is likely to choose the supplier who has provided the best service. I am confident that it will work well in our case.

Well, the expansion joint, as we have already mentioned, is defined by the type of bridge and the movements it experiences. It depends on factors such as the location of the bridge and the traffic it carries.

A bridge in a flat area is different from one in a mountainous region.

A straight bridge is different from a curved one.

A 20-meter bridge is different from a 200-meter viaduct.

The requirements are different for a bridge that needs to withstand temperatures of -20 degrees compared to one that doesn’t or one that needs to withstand 90 degrees, and so on.

All these design factors determine the type of joint and materials to be used. Engineers are guided by these factors when selecting the appropriate joint for each bridge they design.

While we mainly talk about expansion joints in the context of bridges, they are also used in other structures. For example, they are commonly used in parking structures or buildings. Airports have many expansion joints, particularly in areas with gaps, such as parking structures. However, the movements in these applications are usually smaller compared to bridges. About 90% to 95% of the expansion joints we sell are for road bridges and civil engineering projects, while a smaller portion is used for repairs, parking structures, or multi-story buildings.

It’s true that in non-bridge applications, one of the primary purposes of expansion joints is to mitigate noise.

Regarding installation, while I’m not the architect or the construction worker who actually installs them, I can provide some general information.

The installation of expansion joints, specifically for bridges, is much more complex than that of a bearing. It involves cutting the bridge and creating a bed with special cement. Then, the joint is anchored using screws, bolts, and other fasteners, along with a mounting kit. All of this is done under pressure. In other words, installing an expansion joint requires a specialized team with special machinery because it involves cutting the asphalt and disrupting traffic. In fact, we don’t handle installations ourselves. We collaborate with companies that specialize in installation, or we offer the option of purchasing the joint without installation, as installing bridge expansion joints requires a different set of skills.

The expansion joint is designed to withstand external factors, which include movements and weather conditions such as heat, cold, etc. However, similar to supports, proper installation is a crucial aspect for the durability of the joint. If a joint is installed protruding from the asphalt, it can get damaged within a couple of days, or if it is placed in an area where snowplows pass, they can break or cut it. The longevity of the joint largely depends on its installation and external factors, particularly ensuring it is properly installed. In the case of snowplows, they can cause damage, but ultimately, having the joint well-installed is the most important factor for it to last 5, 10, 20, or 30 years.

As we discussed earlier, just like supports undergo a series of mechanical tests and you have the machinery to verify them.

The expansion joint is different in that sense from elastomeric bearings because the bearing is designed for each specific use, with different sizes and shapes. Therefore, it needs to be tested almost always since there are many models. However, with the expansion joint, there are 15 models, and the same one is always sold.

So, what is done? When the model was designed, tests were conducted in external laboratories to guarantee that it withstands certain movements, forces, and a series of tests that the joint undergoes from the beginning. But once those tests are completed, as long as the geometry, materials, and other factors remain unchanged, there is no obligation to conduct any further tests.

You sell a designed joint that can withstand a certain range of movements, and that’s it. Once in its lifetime, you can continue selling them with the same design without any variations, and there is no need to guarantee any additional tests, except for visual inspections to ensure it is properly finished and visually sound.

Earlier, you mentioned that if a piece is installed incorrectly, it can deteriorate. What problems can arise in such cases?

The expansion joint, what happens is that the surface rubber wears out over time, and if it is not properly installed, the surface deteriorates and eventually the steel components start to become exposed. In other words, the joint gets damaged and fails to perform its function.

The basic maintenance for the joint is proper installation. If the joint is well installed, cars can pass over it and the rubber is formulated to withstand friction without any issues. However, if the joint is not properly installed, it can break or deteriorate due to expansions, causing the surface to peel off and exposing the steel components, ultimately resulting in complete destruction of the joint.

The most common types of rubber expansion joints come in a wide variety, but generally, an expansion joint is a flexible structure with the ability to compress and expand, used wherever there is movement of materials.

There are countless types: compact rubber, sponge rubber, joints for bridges, bridge bearings, and a wide variety.

As for the most common ones, I couldn’t specify a single one as they are all very common

Expansion joints for bridges come in many types, including metallic and rubber ones. The types depend on the movement the joint needs to absorb. In other words, there are joints for small movements and there are joints for much larger movements. It depends on the type of movement, the bridge’s gap width, and whether the movements are horizontal or vertical. For each type of movement, there is a joint designed to accommodate and absorb it, preventing it from being transmitted to the structures.

Expansion joints for parking garages are usually designed for small movements and are typically made of either constructed rubber or a metal structure that allows for movement while covering the garage gap. Their purpose is to mitigate noise when a vehicle enters or exits the garage.

I have another question regarding the topic of these rubber expansion joints because I hear the terms ‘elastomeric joints’ and ‘expansion joints.’ I’m not sure if an elastomeric joint is the same as an expansion joint or what the differences are if they are not the same.

An elastomeric joint and an expansion joint are essentially the same. The term ‘elastomeric’ is used to indicate that it is made with an elastomer, which is typically natural rubber, neoprene, SBR (Styrene-Butadiene Rubber), and other elastomeric materials. This term is used to distinguish them from metallic expansion joints, which do not contain rubber components.

When it comes to elastomeric joints in general, there are many because, as we’ve mentioned, there are many different types of elastomeric joints. However, if we are talking about bridge expansion joints, the number of companies is much smaller. Apart from us, there are five or six manufacturers to supply the local market, and usually, at the international level, we also operate in the same countries in the Middle East, South America, and other regions. Three or four, or maybe five companies, tend to compete in these markets.

Well, an expansion joint is usually a special type of joint that we don’t manufacture. It expands with moisture and is typically used to isolate structural elements, such as floor slabs. While it contains an elastomeric component, it’s not typically made of rubber; it’s often constructed from materials like polyurethane or other similar substances, and this is what is referred to as an expansion joint.

As for the advantages of rubber as a material for expansion joints, there are many. Rubber has the ability to expand and return to its initial state, along with resistance to temperature and friction. It possesses several characteristics that other materials often lack, as they may be more fragile, prone to breaking, and unable to withstand temperature variations or regain their original shape. Rubber, therefore, is a highly suitable material for this type of joint.

Well, in terms of expansion joints for bridges, we are currently in the process of conducting tests to establish a standard for CE marking in the European community. However, we are not aware of any manufacturers that have their expansion joints officially certified. What we do have, though, are mechanical tests conducted by external laboratories, which the joints must pass to be used for the specified movements, whether it’s for 50, 100, 200, or any other range. These mechanical tests are in compliance with the EN 377-3 standard, which also covers the homologation of the material mix, the type of mix used, the type of steel, and the manufacturing process. So, the aim is to establish a marking system with full homologation for the material mix, and that’s the direction we are heading.

Because we can see this is also coming up in the questions we’re discussing, but we don’t understand the difference between a standard or regular rubber expansion joint and a reinforced rubber expansion joint.

The difference between a standard rubber expansion joint and a reinforced one is that they are essentially two different products. A standard rubber expansion joint is simply made of rubber, while a reinforced one, as the name implies, contains either some form of metal insert inside it or on its exterior, reinforcing it with steel, for increased hardness, or with fabric on the interior, which enhances the rubber’s resistance to tearing, basically.

Expansion joints are primarily used by large companies, typically in the field of civil construction or maintenance. For instance, they may be purchased by entities like ‘Api Mobility,’ but they are also increasingly in demand from national-level maintenance companies. Additionally, there is a significant export market, primarily serving businesses involved in civil construction and, more specifically, bridge maintenance.

For example, we have worked with a range of companies, including ‘Tecón’ (a small local company), ‘Técnicas de Construcción del Noroeste,’ which is quite small but keeps us busy. We have also worked with ‘Mavi,’ an Italian company, ‘Atlas,’ ‘Reacte,’ a Colombian company, and recently, we have initiated a partnership with ‘Pontix,’ a Mexican company. We are also collaborating with a Bulgarian company called ‘Astra’ and several Portuguese companies engaged in construction. These are specific examples of projects in which we have supplied expansion joints, both in Spain and abroad.

We have worked on virtually all the roads in Spain because we handle maintenance for most of the country. For instance, we’ve worked on the A7, the A2, the M50 in Barcelona, where we did the entire Balsa Viaduct, which features our expansion joints and large supports. We were also involved in the Centenario Bridge in Cadiz.

Currently, we have numerous projects in Galicia, where we supply nearly 90% of the expansion joints. We are also heavily engaged in Asturias, including work on supports for structures, like the Bernabéu, which we have provided supports for.

We have supplied supports for the Torre Colón, including the full supports when it was emptied. At Manises Airport, we have delivered part of the project and have more pending. We have also provided supports for countless prefabricated warehouses for Amazon and Mercadona, which all feature rubber supports at their base.

We have worked with the paper mill in Fuenlabrada and supplied numerous expansion joints along the A2 highway as well.

Well, I’ll tell you a funny anecdote. Some French clients came to visit us as we were trying to sell rubber expansion joints. We received them at the factory and showed them all the production systems. They expressed their interest in seeing one of our expansion joints, so we took them to Madrid to see the bridges where we had sold our elastomeric joints.

On occasions like this, we usually take the client to the bridge to show them our joints. However, it can be tricky to distinguish which joints are ours. So, at one bridge, we stopped to show them one of our joints, but it turned out to be a product from a competitor. We had to quickly redirect them to another bridge where we had our elastomeric joints installed. It’s a funny anecdote.