Determination of the service life of concrete sealers on horizontal and vertical bridge members

Abstract

Due to the increasing rate of deterioration of concrete bridges caused by exposure to chlorides, it has become apparent that effective protection methods need to be employed which will prevent chlorides from reaching critical contamination within the life of the structure. One method of protection is the application of concrete surface sealers which form water-resistant barriers and reduce chloride intrusion. It is imperative to know how effective sealers are and how long sealers retain their effectiveness in order to plan reapplication and estimate life cycle costs for comparison to other maintenance activities. This research was conducted to predict the service life of concrete sealers for both horizontal and vertical bridge components. As a secondary goal, the use of a rapid, non-destructive Surface Absorption Test (SAT) was investigated as a possible substitute for analyzing the condition of sealers. This was done by comparing SAT results with the standard concrete sampling and chloride analysis technique typically employed.

Four sealers were applied to horizontal laboratory specimens (slabs), vertical laboratory specimens (wall sections), and bridges (high-volume and moderate-volume). Control sections were also included in all specimen types. The laboratory specimens were exposed to a 3% NaCl solution for 30 1-week cycles, each cycle being three days of exposure and four days of air drying.

Background chlorides and the chloride ion profiles were determined after 10, 20 and 30 cycles of saltwater exposure. The surface absorption test was conducted at various intervals throughout the cycles. The surface absorption test was also used to attempt to measure the traffic wear effect on the field specimens.

The results indicate that the two epoxies exhibited very little effectiveness in preventing chlorides from entering the concrete. The silane and siloxane sealers performed much better in the laboratory settings, retaining over 90% reduction of chlorides throughout the test period. A service life model which includes laboratory performance and considers application exposure conditions is suggested.

It has been discovered that, at present, surface absorption testing may be used on a limited basis to obtain results which indicate sealer effectiveness, but only if the testing occurs under extremely limited or controlled environments.