A number of lengths of stressed post-tensioning strand, unstressed wires from post-tensioning strand and steel coupons, were exposed in the box sections of two externally post-tensioned concrete bridges. Samples were also exposed outside the structures. The temperature and humidity both inside the box sections, adjacent to the stressed samples, and outside the structures were also monitored. Time-of-wetness probes were positioned along the length of one of the structures. The objective was to determine the corrosivity inside the box sections and thus the degree of corrosion protection required by externally post-tensioned tendons. Results over five years indicate that although the corrosivity within a concrete box section is much lower than outside, bare tendons are not an option and some form of corrosion protection is required. (Author/publisher)
Abstract