Durability and behavior of prestressed concrete beams. Posttensioned concrete beam investigation, supplemental laboratory tests of beams exposed from 1961 to 1982

This report is the sixth in a series describing a study being conducted to develop information on the durability of prestressed concrete beams. This phase of the study is concerned with field and laboratory testing and with observation of posttensioning systems including end anchorages, end anchorage protection, posttensioning conduit, and posttensioning wires. In June 1961, 20 air-entrained, posttensioned concrete beams were placed at the Treat Island, Maine, exposure station. The beams were fabricated using four different types of posttensioning systems with 12 different types of end anchorage protection over external and flush anchorages. End anchorage protection was attached to the beams using six different types of joint preparation: bush-hammering, epoxy adhesive on sandblasted surface, retarding agent, sandblasted, sandblasted with primer, and no preparation. The end protections were made from three different mixtures: portland-cement concrete, epoxy concrete, and sand mortar. Eight beams were returned to the Waterways Experiment Station (WES) for autopsy and testing in September 1973 and December 1974. These beams were tested to determine the effects of severe environment described above on the posttensioning system. In January 1983, three more beams were returned to WES from Treat Island for autopsy and additional testing. The results of these additional tests are the subject of this investigation. If no further tests are made on the nine posttensioned beams that remain at Treat Island, this report will be the final report in the series.