Dowel bars are a critical structural component in jointed concrete pavements. As increasing emphasis is placed on the need for long-life pavements, it becomes extremely important to use construction materials that are capable of performing satisfactorily for service lives of 50 years or more.
Corrosion of steel reinforcement dowels in concrete highway joints is a major cause of premature concrete pavement failure. This corrosion is caused by the migration of ions from harmful de-icing salts such as magnesium and calcium chloride. The chlorides travel through the joints and porous concrete towards the steel reinforcement surface to break down the passive film that normally protects the steel and causing the conventional dowels to rust.
Having a volume that is 6-10 times greater than the original steel consumed, this rust not only impedes the essential movement of the dowel in the joint but also exerts considerable internal pressure on the concrete itself. The result is the premature failure of the pavement joint that can be visibly seen as cracking and spalling. This issue is the main contributing factor that significantly reduces the intended life of the pavement serviceability.
Passive cathodic protection is an accepted form of corrosion protection. Jarden's Lifejacket® dowel utilizes proven Zinc anode technology to protect the steel reinforcement dowels from corrosion. The Lifejacket® dowel is produced by mechanically bonding solid Zinc strip to the standard ASTM A 615 steel dowel bar, thus providing two-fold protection.
The thick layer of Zinc acts as a surface barrier to chloride ion attack and is over 20 times the thickness found on a normal galvanized bar, thereby providing a more resistant surface to breach, scratches, and wear abrasion.
In addition to acting as a barrier, the Zinc layer provides cathodic protection to any exposed steel. In the presence of salt water, the natural electro-potential differences between steel and zinc create a galvanic cell; whereby, the polarized steel bar is protected preferentially by the zinc.
The Lifejacket® dowel provides a long-term, cost effective solution to concrete highway corrosion problems and is one of the major components used in long life concrete pavements.