When selecting a building material for an infrastructure project, there are a few key factors to consider before making a decision. Engineers must be sure to make selections that will benefit both the people within their agency, who will be working with the material, as well as the project’s end users.

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One such material is fiber-reinforced polymer (FRP), which can be hugely beneficial for both builders and users. Read more below to find out how this unique material can work for you.

1. Production and Installation Time

When developing the design for your overall infrastructure plan, it’s important to factor in the amount of time that will be needed not only for the whole project, but also for each step within the process. Obviously, saved time translates to saved costs, but you certainly don’t want to sacrifice quality for efficiency. FRP can provide an ideal balance, helping to save valuable production time while still providing the necessary quality, strength and durability. Below, compare the production and installation time of FRP to that of precast concrete:

As you can see from the chart, FRP’s total production time is 15 days less than that of precast concrete. This translates to more than two weeks’ worth of saved labor costs and overall downtime for infrastructure development. FRP also requires less total installation time than precast concrete — almost five days less, on average.

Thanks to this shorter installation time, engineers using FRP don’t have to complete their work solely during the workweek. Instead, they can opt to do installation work on the weekends, too, when there is less traffic congestion and end users will experience less inconvenience and fewer interruptions to their commutes.

2. Weight

Going hand-in-hand with a quicker installation time is FRP’s weight. FRP is known for being lightweight. In fact, it’s about eight times lighter than reinforced concrete — meaning FRP is also less labor-intensive to use and install, and requires less equipment. This material also requires less labor during removal processes. See below to compare the total weight of FRP to the total weight of precast concrete.

As you can see from the chart, FRP is significantly lighter than precast concrete, with an FRP panel weighing about 5,000 lb and a precast concrete panel weighing nearly 41,000 lb. Using a lighter material makes it easier on your workers, saves on labor costs and places less stress on the infrastructure. The lower the weight of the material being used, the less wear and tear the infrastructure will experience as a whole.

3. Corrosion and Maintenance

Offering high durability and strength, as well as reliable resistance to corrosion, FRP is long-lasting and mitigates the need for ongoing maintenance. The lack of frequent maintenance and repairs helps to save on expensive labor and material costs and also prevents inconvenience to end users, since repair downtime is minimized.

And, since FRP is long-lasting and resistant to corrosion, the long-term costs end up being less as well.

Though FRP does have a slightly higher price point per square foot at initial installation, the material allows for many benefits in terms of long-term cost savings. Because FRP causes less stress on the infrastructure and is more durable than other materials, it diminishes the need for costly repairs or reconstruction down the road. For example, bridges and platforms constructed from materials such as reinforced concrete, steel, or wood often fall apart 15 to 20 years after initial installation — requiring extremely expensive repairs or even a whole new investment to rebuild from scratch. FRP, however, is built to last and won’t experience corrosion over time like many other construction materials.

4. cost savings

FRP structures are highly reliable and low-maintenance, but they shouldn’t be considered maintenance-free. Repairs requiring field service will need to be performed on rare occasions. Performing yearly routine inspections (at minimum) will help ensure potential issues can be caught before they become a problem. If an issue has been identified and reported (ex. cracks, crazing, discoloration, excessive wear, etc.), a field service technician will be sent out to complete the repair.

As mentioned, structures made from steel, concrete and wood are prone to regular repair work, as well as those made with brick and tile – that’s also where FRP can come in. Fiberglass can be used for patch repairs on bridge decking and liners can be applied to culverts, pumps, storage tanks and pipes to protect less-resistant materials from future damage. FRP can even be used for wrapping bridge piers and columns.

Repairs made with FRP add up to long-term cost savings. Since the material is corrosion-resistant and has a much longer service life, it’s a great option to use when repairing and protecting existing structures. Take a look at our brief case study to learn more about how FRP repairs reduce costs.

5. design flexibility

FRP is ideal for any type of job that requires customization, as it is engineered to meet exact specifications. Regardless of complexity, engineers can create panels of all different sizes and shapes. This allows for aesthetic versatility, as there is a range of possible colors. It is also possible to add functional features to facilitate a smooth and easy installation process.

For more information, please visit Tunnell Lliner.

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FRP offers a wide range of unique benefits — short production and installation time, light weight, long-term cost savings, corrosion resistance, and superior longevity. An ideal material for use in almost any infrastructure project, FRP is very dynamic, making it the perfect choice for all types of infrastructure — including vehicle, pedestrian, and trail bridges, cantilever sidewalks, rail platforms, waterfront frameworks, storage tanks and pipes, stairs and handrails, and much more.

Segmentally lined tunnels use a large quantity of concrete, with the associated carbon burden that brings. However, rethinking your approach early on can reduce the carbon footprint they leave. We take a look at 10 ways you can reduce segmental tunnel linings’ carbon footprint...

1. Reduce the amount of cement used in tunnel construction

Cutting down on the amount of cement you used can make a massive difference. In fact, with as much as two-thirds of carbon emissions resulting from cement usage, it’s probably the single most important measure you can take. Strength boosting admixtures such as Master X-Seed permit a reduction in the total cementitious materials content while maintaining compressive strength with associated benefits in CO2 reduction.

Addressing the issue early on is key – which means thinking about carbon emissions at the design stage. Consider the aspects of your design that could make the most difference to lowering the CO2 emissions, including:

• Tunnel alignments
• Structural support
• Excavation methods
• Material selection

Making decisions too late on any of these aspects reduces the potential to cut carbon significantly.

2. Include life cycle assessments (LCAs) at the design stage

Life cycle assessments (LCAs) calculate the potential environmental impacts of a product system throughout its life cycle. ISO Sustainability in buildings and civil engineering works specifies four life cycle stages:

• Production (A1-A3)
• Construction (A4-A5)
• Use (B1-B7)
• End-of-life (C1-C4)

For tunneling projects, it’s essential to add the design phase to these LCA stages. Even though no relevant emissions result from the design process itself, its influence on later emissions is highly relevant.

3. Consider the implications of early design decisions carefully

Early design decisions can make a big difference to CO2 reduction. Thinks about the following as you assess the environmental implications:

• What are the alignment variations?
• Will you opt for twin tunnels or one large tunnel?
• Do you plan to excavate with a TBM rather than NATM?
• Will you choose a single shell, double shell or composite lining?
  
  

The decisions you make will determine how much concrete the project will use and its quality, and dictate the mix designs needed to fulfil your engineering and placement requirements.

4. Understand the impact of the construction phase

In any tunneling project, greenhouse gas (GHG) emissions are very high during construction, firstly because of materials’ manufacture and secondly because of the construction activity itself.

Beyond initial construction, the need for future maintenance, and the likely scale of remedial works during the use phase, are dictated by the skills of the workforce and material selection during construction. The knock-on effect on later CO2 emissions can be significant – less durable construction leads to more emissions due to more frequent and material-intensive maintenance needs.

5. Think about transportation

The choice of transportation modes and distances for raw materials can have a significant effect, too, so you should analyze this separately for each project.

In practice, owners should incorporate sustainability targets and carbon budgets when putting contracts out to tender, and these elements should form part of the contract documents. Stating a clear commitment to sustainability paves the way for innovative, sustainable tunnel construction that factors in reduced use-phase maintenance and repair – and hence emissions – thanks to more durable, resilient designs. Currently, the purely capital cost-driven approach to construction only addresses emissions reductions as an afterthought.

6. Compare design options from a CO2 reduction perspective

When weighing up the design options, take CO2 emissions into account as you make a decision. For example, one larger-diameter tunnel appears to be better than two smaller twin tunnels for carbon emissions, purely from a structural support perspective. Here, the large tunnel might be the better option when the free space is fully used, although two smaller tunnels could be preferred for safety reasons when traffic is involved.

7. Optimize your concrete mix design

Once you have settled all of the fundamental design decisions, you can optimize the concrete mix design to improve sustainability and achieve significant carbon reductions. For segmental tunnels, optimizing mix design can lead to a 20 % reduction in the carbon footprint of materials for the lining, or around 15 % of the total project footprint.

The key factors here are the total amount of cement and the cement type. As you weigh up the options, consider the need for 28-day concrete strength versus 56-day testing, if the full load-bearing capacity might not be required at a young concrete age. If higher early concrete strength is essential to allow the handling and bedding of prefabricated segments, assess whether concrete admixtures like Master X-Seed could be used to boost strength, adding less total carbon to the mixture than increased cement content.

Different types of cement give varying levels of embodied carbon, so another consideration is increasing the cement strength class. While this can increase carbon emissions per kilogram of cement, it reduces the overall cement amount in the mixture. Reduced clinker content significantly lowers the global warming potential of the cement. Achievable reductions will be affected by regional variations in raw materials, energy sources and production processes.

8. Look at the reinforcement and curing

Looking beyond the mix design, the choice of reinforcement and the curing method for the segments may also contribute to the carbon burden. Steel bar reinforcement, for example, is heavy, difficult to handle, and prone to corrosion but sometimes unavoidable. Structural fibers can partially or completely replace the steel bar reinforcement. Mixed into the fresh concrete, the fibers (e.g. MasterFiber) form an internal network and add superior tensile properties to the concrete elements. The result is improved crack control and stronger concrete, which in turn leads to less maintenance work and overall longer service life of the tunnel structure.

9. Don’t overlook the CO2 contribution of annulus grouting

The annulus grout fills the overcut of the cutter head around the segments, stabilizing them and allowing the load from the ground to transfer homogeneously onto the segments. It’s a significant carbon contributor in tunnel construction materials, and, crucially, there is a big difference between the broader environmental impact of different types of grout.

Two-component grouting systems are increasingly widely used, mainly because of ease of application; they comprise a cement-water-bentonite component and a water glass (sodium silicate) component for gelling and strength gain. The environmental concerns involve the high pH level of the water glass, potential leaching effects, durability concerns, and the need for increased cement content.

The biggest reduction in carbon relating to the grout comes from switching from a two-component system to a single-component grout with lower cement content where possible. However, future-oriented innovation opportunities that meet owners' expectations for quality, durability, and carbon footprint may lay somewhere between the two solutions mentioned above.

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10. Encourage innovative approaches