When designing bridges, engineers carefully select materials that can handle the forces they are expected to experience during their lifetime. Typically, ductile materials such as steel and concrete are used for components that must be able to withstand tensile forces.
Some new construction materials are being used to enhance sustainability in bridge design. These include self-healing concrete and shape memory alloys.
Self-healing concrete
Self-healing concrete is a new material that can repair cracks on its own. It is especially useful for large structures that are not easily accessible for maintenance, such as bridges. This technology can be used to keep water from seeping in and damaging the structure, and it can also prevent corrosion of steel reinforcements.
This technology works by incorporating bacteria and self-healing microcapsules into the concrete mix. The bacteria consume the oxygen that causes steel corrosion and create a calcium lactate solution, which hardens the concrete around them. The microcapsules contain healing agents that can seal cracks as soon as they form.
These self-healing materials are injected into the concrete during construction. They can then automatically fill the cracks as they grow. They can even close dry shrinkage cracks, reducing the risk of damage. The concrete is more durable, too, and has fewer phreatic joints than traditional concrete.
Self-healing concrete has the potential to revolutionize the construction industry, slashing repair costs by filling cracks as they form. Scientists are working to improve the performance of this material so that it can be used in more applications. While many companies are experimenting with this technology, only a few have begun to use it in real-world projects.
Shape memory alloys
Shape memory alloys, or SMAs, are a class of “Smart Materials” that can exhibit unique thermomechanical phenomena, including the shape-memory effect and pseudoelasticity. They can be shaped in the martensite phase by mechanical stress and then reverted to their original form upon heating. SMAs also possess a high work output and fatigue resistance, and are available in a wide range of shapes.
Currently, the most popular SMAs are NiTi-based alloys. These alloys are commonly known as nitinol (the name is derived from the combination of the abbreviation of nickel and titanium). The transformation temperature of these alloys can be adjusted by adding elements such as Pt, Hafnium, or Zr to the alloy. SMAs can be used to create a variety of structures, such as stents, guide wires, and flaps for air-conditioners.
The ductility of SMAs makes them an excellent material for shear reinforcement. Research on the use of iron-based SMA for shear strengthening began in 2001, and the results have been promising. In fact, the researchers have already successfully shear strengthened RC beams in the laboratory and on a real bridge.
In the future, SMAs may be used to make a concrete bridge more resilient during an earthquake. They can be incorporated into the piers of a concrete bridge to allow them to self-center and remain in their correct positions after an earthquake. This will reduce the amount of damage to a bridge and improve its functionality.
Composite material
Composite material is an innovative construction material that combines natural and artificial materials. The result is a material that is stronger, lighter, and less expensive than traditional building materials. There are two constituent parts to a composite material: the reinforcements and the matrix. The reinforcements can be made from any number of materials, including metals, plastics, wood, or other natural materials. The matrix is a material that holds the reinforcements together and gives it strength. Composite materials are ideal for infrastructure applications because they can withstand high loads and are resistant to corrosion.
The use of composites in bridge construction is becoming increasingly common. This technology is especially useful in accelerating bridge construction and reducing maintenance costs. This type of technology is also suitable for long-span bridges that require heavy load capacities. Moreover, composites can be used in conjunction with other advanced technologies to increase the speed of bridge construction and reduce the overall cost of a project.
A good example of a composite is concrete, which is made from aggregate (small stones or gravel) bound together with cement. The aggregate provides strength under compression, while the cement is strong enough to handle tensile forces. Composites can also be reinforced with wires, meshes, or rods to increase their tensile strength. For instance, a composite of graphene and copper is 500 times stronger than copper alone.
Timber
Timber is an old material that has long been used in bridge construction, but new technology has made it even more sustainable. It is now possible to use plant fibers, such as flax, combined with a special bio-resin to create a light and durable composite material that can withstand the same load as aluminium or steel. The result is a completely sustainable product that will also help to reduce environmental impact. The first of these bridges has been built, and more are planned. The plant fibres will be sourced from non-fossil sources, and the resin will be produced from waste products like bio-diesel production and recycled PET bottles.
Advances in timber material development and construction have also made wooden bridges more competitive for moderate spans. In addition, wood can be shaped to fit into environmentally sensitive areas where it isn’t practical to bring in heavy construction equipment. These innovations have led to the creation of new bridge materials and techniques that can be used in harsh environments.
One of these is the Geosynthetic Reinforced Soil Integrated Bridge System (GRS-IBS). This technique uses geotextile reinforced soil sheets alternating with layers of compacted fill. This method eliminates the need for joints and deep foundations, which cuts down on construction costs and time. It is also easy to maintain and can withstand a variety of weather conditions.