Extending the Service Life of Bridges Through Proper Compaction of Asphalt Decks

Bridges are major components of the highway infrastructure and play important role in the development of societies and their economic growth. The safety and performance of bridges do not depend on design and construction of its structural members alone but also on the degree of protection provided by the asphalt layer added to provide a comfortable ride as well as significant protection against penetration of water and other harming materials to the main structure of the bridge. Compaction of the asphalt deck of the bridge is done only by static rollers while vibratory rollers are not allowed on the deck. However, steel rollers, static or vibratory ones, induce hairline cracks during compaction which allows water, salt and other harmful materials to penetrate through the asphalt deck and reaching the main slab of the bridge which may be made of reinforced concrete or steel members. The presence of water and salt can speed the process of corrosion leading to earlier than expected deterioration of the bridge and in some cases failure of the entire structure. The Ministry of transportation of Ontario (MTO) has used a new asphalt compactor termed Asphalt Multi-Integrated Roller (AMIR) which provided a much tighter asphalt mat with significantly improved permeability performance, higher densities and abilities to compact thicker layers with higher efficiency and less number of passes when compared to current steel rollers. The results led the MTO to include permeability measurements into its Q/A and Q/C requirements for bridge asphalt decks. This paper presents the outline of utilizing AMIR compaction technology on three MTO bridges, the results of field permeability measurements of asphalt sections compacted side by side using AMIR and steel rollers, and laboratory test results. The results showed that the AMIR technology will provide better protection to bridge deck and its steel structure and reinforcement; leading to longer service life with less frequent maintenance. Finally, the paper includes preliminary economic analysis showing the gains and benefits resulting from adopting the new technology to the main parties involved with highway assets.