Citation
Abstract
It was noticed in 1977 that exposed surfaces of the reinforced concrete foundation of the DSS-13 26-meter antenna were exhibiting relatively light cracking. By 1980 the cracking had worsened to the point were it was decided that an investigation should be undertaken to establish the cause and, as needed, devise a repair technique that would maintain the serviceability of the antenna. Core samples were obtained from the concrete and various laboratory tests conducted. In-place nondestructive type tests were also performed, The tests established that the concrete was deteriorating because of alkaliaggregate reactivity. This is a phenomenon wherein certain siliceous constituents present in some aggregates react with alkalies in the portland cement to produce a silica gel which, in turn, imbibes water, swells, and cracks the concrete. After a thorough structural analysis, a rehabilitation scheme was devised and installed. The scheme consisted of a supplemental steel frame and friction pile anchored grade beam encircling the existing foundation. This system provides adequate bracing against base shear and overturning due to seismic loading. Larger cracks were sealed using a pressure injected two-component epoxy.
Details
- Volume
- 42-78
- Published
- August 15, 1984
- Pages
- 160–171
- File Size
- 790.3 KB