Development of a high-performance waterproofing system for reinforced concrete slabs
-A study on extending the service life of highway bridges-

Examples of damage to highway bridge RC slabs

Random wheel running machine for frost damage testing

Conceptual diagram of a high-performance waterproofing system for highway bridge RC slabs

       

In recent years in Japan, deterioration and damage have become increasingly apparent on reinforced concrete (RC) slabs of highway bridges characterized by heavy traffic and those designed and constructed in accordance with old standards. Such damage, which includes cracking in asphalt pavements and collapsed slabs, has become a major road management issue because it affects driving safety and may even result in injury to third parties at overpasses and overhead crossings.

It is known that highway bridge RC slab deterioration and damage can be accelerated in cold snowy climates like that of Hokkaido due to frost/salt action associated with the use of deicing agents.

The influence of water is also seen as a major factor contributing to this type of damage. In order to eliminate such influence, waterproofing is applied to the entire surface of newly constructed RC slabs.

However, many RC slabs on existing highway bridges are not waterproof, and in some cases problems have been found in slabs that were re-waterproofed when pavement was replaced and in slabs that were waterproofed relatively recently. RC slab damage is also expected to increase in the future because the conditions of cold snowy regions are not fully taken into account in the current rules and regulations for waterproofing systems. To enable appropriate maintenance of highway bridge RC slabs, it is necessary to establish countermeasure implementation methods and techniques that are effective in terms of prevention and maintenance.

Against this background, the purpose of the present study was to support the development of a high-performance waterproofing system to RC slabs suitable for the harsh conditions of cold snowy environments.

In the study, analysis of deteriorated and damaged RC slabs, waterproofing systems used for existing highway bridges and environmental conditions was performed to identify the functions required of waterproofing systems. Various elements were examined, and various structures consisting of an asphalt pavement, a waterproofing system and an RC slab was tested with a random wheel running machine used for frost damage testing to verify adhesion performance and frost resistance. In this way, a method for assessing the effectiveness of high-performance waterproofing systems , a technique for treating the surfaces of RC slabs in waterproofing work, and a high-performance waterproofing system that incorporates a drainage structure are studied.

(Contact: Structure Research Team, CERI)