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Figure 1 Figure 1 is a photo showing a close up of a preformed silicone bridge joint system/>  </div>
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Fig. 1. A close up of a preformed silicone bridge joint system.
            

Selecting a Bridge Joint System
Joseph Becker, RJ Watson, Inc

When beginning any discussion on bridge joint systems one must consider the purpose and function of the bridge joint in today’s modern highway system. A bridge joint can be likened to the roof on your house. They protect very expensive components underneath. Damaged and leaky bridge joints are the cause of millions of dollars of substructure damage per year due the damaged joint allowing the passage of liquid and debris from the deck of the bridge to the girder and bearing assembly’s below. This damage usually extends to concrete pier caps as well and its typically exacerbated by the application of deicing salts and liquids in certain climates.

When selecting a bridge joint system one must consider several factors. The bridge joint system must eliminate the passage of liquid and debris, it must be accurately sized, the material properties must be contusive to the application. In order to offer guidance its best to consult directly with a manufacturer of bridge joint systems such as R.J Watson, Inc who has decades of experience in the design, manufacture, and installation of bridge joint systems.

Many systems on the market today can be considered legacy systems. These systems have been in use for a very long time and do not have a excellent track record of success. Neoprene based compression seals, poured silicone joints and strip seals are all very common fixtures on the roadway today. Fortunately over the years extensive studies have been done to try and determine the main causes of failures in these bridge joint systems. While no study is completely conclusive due to the different climatic conditions across the country it has been noted that neoprene based systems have a inherent tendency to become brittle and take what’s known as a compression set over years of being installed on a structure. This is due to their organic material properties breaking down under U.V. exposure. These systems also rely completely on compression to stay in place. It can be difficult to accurately size these types of joints because one must know the exact openings of the structure and the exact movement range of the bridge to the ¼”. Strip seal systems are in wide use throughout the country. The steel extrusions typically last a very long time however they are susceptible to corrosion, plow hits, and rocking loose after years of heavy traffic passing over them. The gland in this system is typically made fof neoprene and is susceptible to the failure modes as compression seals, especially since strip seal systems tend to collect the most debris. This gland is replaceable however it has been studied and shown that this replacement process can be very time consuming and difficult to accomplish out in the field.

Recently a new generation of bridge joint systems has come to market bring with them improved technologies and features that prolong the life of the system and allow easy reparability down the road. One such system is the preformed silicone system Silicoflex offered by R.J. Watson. This system is completely inorganic and is finished in carbon black to make it extremely resistant to U.V. light and greatly decreases the possibility of the gland breaking down over time. The Silicoflex system is bonded to the joint face using a 100% single part silicone adhesive that forms a tenacious bond with concrete, steel, or elastomeric concrete headers. The system is fairly universal in that it can be bonded to just about any existing joint opening. There are only three standard sizes of this system so it is very easy for an end user to determine what size they need. Silicoflex can span ½” to 6.5” openings within the four individual sizes R.J. Watson offers. Because this system is so universal its quickly become a favorite of state DOT maintenance forces who must quickly repair all manner of joint systems in the field on a moment’s notice. Silicoflex has also been called upon frequently in Accelerated Bridge Construction projects due to its ease and speed of installation. The Silicoflex system is now used in rehab and new highway construction and on rail bridges both in the US and abroad. This system, when coupled with a modified improved steel armoring system has also been approved by several states as an equal to the strip seal design featuring the cumbersome extrusions. When it comes to reparability Silicoflex is ahead of the other systems on the market. A small tear or puncture in the gland can be “healed” simply by applying more of the included Silicoflex Locking adhesive extending the life of these systems for years and years.

Always remember when choosing your joint system to request testing data and be sure the supplier your working with has the ability to connect you with the right system for your project and for your budget. When you consult with the industry experts at R.J. Watson, Inc you can be sure that they will work with you to ensure you have a system that will last and preform as promised.