Title: Observations and Testing of Post-Tensioned Beams Exposed to Severe Weathering for 33 Years

Author(s): Morris Schupack and Edward F O'Neill

Publication: Symposium Paper

Volume: 163

Issue:

Appears on pages(s): 383-408

Keywords: adhesives; anchorage (structural); concretes; corrosion; durability; freeze thaw durability; grout; joints (junctions); post-tensioning; prestressing; prestressing steels; unbonded prestressing; Materials Research

DOI: 10.14359/1367

Date: 8/1/1996

Abstract:
To determine the most effective end-anchorage protection for post- tensioned beams, 20 air-entrained post-tensioned concrete beams were fabricated and placed at the Treat Island severe exposure station in 1961. The beams were fabricated using four types of post-tensioning systems with 12 different types of end-anchorage protection over external and recessed anchorages. End- anchorage protection was applied to the beams using six different types of joint preparation: bush-hammering, epoxy adhesive on sandblasted concrete 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-cement mortar. The 20 post-tensioned test beams have been inspected annually by the Corps and biennially by other interests. Eleven of the beams were autopsied at the Waterways Experiment Station (WES) in 1973-74 and 1983. This paper assembles the data obtained, evaluates the data, and summarizes the important findings related to durability. The main findings are that the flush (recessed) anchorage protection using portland cement concrete is the superior detail. The external portland cement concrete anchorage protection, properly anchored with reinforcing steel across the join with adequate concrete cover, also provides an effective protection.