NJTA 9 Bridges – AAR Assessment

Condition assessment & service-life evaluation

The New Jersey Turnpike is a toll road in New Jersey, maintained by the New Jersey Turnpike Authority. According to the International Bridge, Tunnel and Turnpike Association, the Turnpike is the nation’s sixth-busiest toll road and is one of the most heavily traveled highways in the United States.

The Turnpike is comprised of approximately 600 bridge structures divided into nine Districts. Most of these structures were built over 60 years ago and were exhibiting different signs of degradation such as extensive cracking, and Alkali Aggregate Reaction (AAR).

SIMCO was hired to assess the levels of AAR affecting the structures and provide the necessary recommendations for mitigation strategies to be used for the efficient rehabilitation of the deteriorating substructure elements.

SIMCO’s scope of work consisted in the evaluation of twenty-one (21) elements from nine (9) bridges identified. The main objective was to conduct a field investigation of each substructure and document the nature and extent of the damage. SIMCO’s work also involved providing recommendations for the most efficient repair strategies and associated lifecycle costs.

Following a visual inspection, it was apparent that the degradation was found to vary significantly from one element to another. Major defects were mainly observed in areas where concrete was most exposed to water, such as tops of columns, abutment seats, ends of piers and pile caps. Defects consisted mainly of cracks and delamination and visual observations suggested that degradation was resulting mainly from Alkali Silica Reaction (ASR) and reinforcing steel corrosion. These two mechanisms often have a synergistic effect since cracks created by either one, if large enough, can create preferential pathways for water and chloride ingress, which can lead to further concrete degradation.

Different techniques were combined to fully characterize the mechanical properties and the internal deterioration of concrete as well as the reactivity of concrete aggregates. The presence of ASR was confirmed on the tested structures and the results indicated that the severity of the ASR degradation was not always in line with visual degradation ratings. Aggregate reactivity was found to vary from low to high according to the structure considered.