Bayonne Bridge Abutment Rehabilitation

Upon opening, the Bayonne Bridge was awarded the distinction of being "the most beautiful bridge of steel erected" by the American Institute of Steel Construction. The 26,000 tons of structural steel also make the Bayonne Bridge the fourth largest steel arch bridge in the world. But in recent years, the concrete of the New Jersey abutment began showing signs of deterioration and cracking. Modjeski and Masters' (M&M) experienced team of technical experts identified Alkali-Silica Reaction (ASR) as the cause of the concrete cracking – a condition resulting from the internal expansion of a resultant gel that is produced when silica-laden aggregate is subjected to moisture.

M&M developed an innovative solution to arrest further concrete cracking in all directions: a post-tensioning design providing tri-axial compressive stress (or tri-axial confinement) greater than the internal ASR pressure. First, our plan called for a high-strength concrete encasement to be constructed around the abutment to minimize moisture penetration of the existing concrete. Next, 181-horizontal P/T tendons and 254-vertical rock anchors were installed to establish the tri-axial confinement. We used coring bits to drill the new concrete for the tendon installation, and rotary percussion drilling was used in existing concrete. To achieve the specified tight drilling tolerances, the contractor employed a high-tech system to continuously monitor and correct the direction of drilling. Low alkali grout was specified to minimize the possibility of replenishing the alkalinity content of the existing concrete. In the end, nearly 5.5 miles of drilling was completed, and nearly 245 miles of P/T strand was successfully installed to neutralize the cracking.