The hidden strength of carbon reinforcements in bridge construction
The catastrophic failure of Genoa’s Morandi bridge in August has only served to highlight how ageing bridge structures must have a maintenance regime that can ensure the safety of road users.
In the UK, rail and road bridges are subjected to many types of loadings and other influences including corrosion which has to be properly managed to maintain safety. With nearly 100,000 road and rail bridges across the country, what proven solutions are available to ensure this vital infrastructure is fit for the future?
Three quarters of all highways bridges consist of reinforced concrete, and whilst concrete accounts for the make-up of the majority of rail bridges, these structures are also made of other materials such as cast and wrought iron. Regardless of a bridge’s properties, the long-term exposure to the elements and traffic-based wear and tear will potentially lead to a number of issues including reinforcement corrosion, excessive cracking, chloride ingress and surface erosion.
The consequences of not addressing bridge repair problems will be costly and possibly even dangerous in the long-run. Therefore, evaluating the causes of the deterioration is just as important and vital to evaluating and offering the correct repair strategy. Testing is a vital part of bridge repair and protection specification. It can be carried out using various techniques including a basic visual survey, hammer testing, chloride analysis techniques, carbonation testing, concrete-to-reinforcement cover surveys and half-cell potential testing. These assessments will help play a part in Sika’s preparation of any project-specific specification offering.
Lifecycle costing and management offers bridge owners the best approach to minimising any closure times whilst increasing required periods between scheduled maintenance works. This helps incur a minimal expenditure over the structure’s full service life. Sika provides bridge owners and their maintenance managers with the right design and planning tools, followed by well-designed and proven refurbishment solutions and systems to considerably increase the time between necessary maintenance and repair cycles.
As the worldwide leader in the structural-strengthening of all types of reinforced concrete structures, Sika provides a full range of fully-tested and approved strengthening systems. Rather than use steel reinforcement to strengthen columns, beams, slabs and wall, specifiers are turning to carbon fibre. Flexible and versatile with a superior strength-to-mass ratio than traditional reinforcing methods, carbon fibre allows for a significant increase in performance without adding additional significant dead load. This solution is less intrusive and quicker and easier to install compared to traditional methods.
Carbon fibre strengthening comes in many different forms, plates, rods, near surface mounted plates, fabrics and shear links and are fixed using a range of high performance structural adhesives. It is increasing in popularity as a proven solution for not only reinforced concrete but also steel, cast iron, wood and masonry structures due to its strength, lightweight, easy-handling ability, durability, superb adhesion and rapid installation where downtime of a structure is in short supply.
By installing Sika CarboDur® for example, it is possible to improve the load carrying capability of the bridge so it can carry additional wheel loads and be fit for modern road standards. Furthermore, ageing bridges across the UK rail industry network, many from the Victorian era, require proven solutions which minimise disruption. This widely recognised and established carbon-fibre reinforced polymer strengthening solution can be installed overnight when using the new Sika CarboHeater® to encourage earlier curing, even at lower temperatures.
Fixing and futureproofing critical infrastructure such as bridges has never been more important. When it comes to the upgrade and maintenance of these vital assets, Sika has the long-term refurbishment solutions that will stand the test of time.
Article by Ronnie Turner, Infrastructure Manager at Sika Refurbishment