Questions and comments poured in from the enthusiastic audience. Can this process be used on my historic concrete arch bridge? How many years can it add to it’s life? Can I use this for my tunnel, retaining wall, and building? What is the downtime?

Questions like these are common as owners, property managers, and maintenance personnel explore the use of vacuum injection and impregnation technology. This process can improve the load carrying capacity and extend the useful life of your concrete structures. It costs less than standard restoration (i.e., removal and replacement of deteriorated components) and in comparison has fewer impacts to traffic flow and facility operations.

And in many cases it is a better investment than conventional restoration, which can be nothing more than a short-term fix unless fracture mechanics are properly analyzed. When restoration failures are analyzed in a forensic environment, they have been found to actually contribute to or accelerate the deterioration process.

The Problem
Can we prevent cracking to begin with? Unfortunately, no. We can only design for and somewhat control or delay it. Once concrete, stone, or masonry starts to crack, it sets the stage for a series of physical changes that can eventually reduce its load-carrying capacity. The propagation of cracks can lead to a number of failures such as:

• Degrading of exposed faces of concrete


• Delaminating of concrete around reinforcement bars


• Debonding of concrete overlays and the creation of voids underneath

Many public works officials have learned that they can avoid these problems or mitigate an ongoing condition with preemptive maintenance, aimed at correcting a problem before expensive
reconstruction is needed. They are finding that preemptive maintenance using vacuum injection and resin impregnation is a superior solution to crack repair and restoration.

Vacuum injection/impregnation is the only method to seal the internal network of voids and micro-cracks that other crack seal systems cannot reach. As a result, concrete deterioration is arrested. Since the path for moisture and air to reach reinforcing steel is sealed, the opportunity for continued corrosion is mitigated. The structural resins used bonds to the concrete and steel to restore structural integrity. The useful life of the structure is extended because the symptom (the crack) is not only treated, the cause (the loss of strength) is addressed.

The Process
Your first step to rectifying a problem is to identify the cause of the disrepair. This is crucial in determining the materials and method of repair to be used. Once you have gone through this process and determined that vacuum injection is your preferred repair technique, here is the general repair procedure:

• Inspect, clean, and vacuum the surface.


• Install resin injection ports.


• Apply a surface seal over the area to be repaired.


• Create a vacuum over the sealed area.


• Evacuate or dry the moisture from the crack network.


• Maintain vacuum and release resin through injection ports.


• Pause while resin absorbs and wicks into the micro-cracks.


• Complete the injection process.


• Move to the next repair section.

Summary
The vacuum injection/impregnation process is a proven tool that you should consider when your bridges, tunnels, retaining walls, and buildings need repair. It is a cost-effective alternative to conventional repair techniques. See Case Study to follow.

It meets stringent design requirements for restoring structural integrity, architectural performance, and historical preservation. It has been accepted, specified, and embraced for bridges, tunnels, and building facade repairs by design professionals, government agencies, property managers, and building owners.

For more information, contact Joe Logan, P.E. at 585-334-1310, x 251 or by e-mail at jlogan@fisherassoc.com.