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Title: Deterioration Survey of Structural Concrete at the Rogun Hydro after its Conservation

Author(s): Vyacheslav Falikman, Komron Safarov, and Valentina Stepanova

Publication: Symposium Paper

Volume: 326


Appears on pages(s): 95.1-95.10

Keywords: AAR; corrosion; hydro construction; sulfate attack; survey

DOI: 10.14359/51711078

Date: 8/10/2018

Rogun Dam is an embankment dam in construction on the Vakhsh River, Southern Tajikistan. The Hydro construction preparatory period was started in 1976. By 1993, the upstream cofferdam height reached 40 m (131 ft) and 21 km (68 898 ft) of tunnels had been driven, and the spaces of the powerhouse hall and the transformer station had been mined. After collapse of the Soviet Union the Hydro construction was suspended. Resumption of construction had required expert investigations including analyses of the earlier built structures. As established, many reinforced concrete components were damaged in underground hydraulic structures. The phase and element composition of concrete core specimens was studied. The analysis data have shown that the structure of sample cores comprises chalcomorphite and thaumasite that gives evidence of the sulfate corrosion process. At the same time, photomicrographs of thin and polished sections obtained using optical and electron scanning microscopes show signs of alkali-aggregate reactions (AAR). AAR is also evidenced by the presence of typical cracks directed radially from aggregate grains deep into the mortar matrix as well as the cracks penetrating the aggregate particle itself. The cracks are filled with the gel-like reaction product. With consideration of the results obtained the recommended commercial concrete compositions will be optimized and studied in detail to avoid the degradation processes of concrete in the future damages hereafter