Performance of Concrete at Treat Island, U. S. A.: CANMET Investigations


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Title: Performance of Concrete at Treat Island, U. S. A.: CANMET Investigations

Author(s): V. Mohan Malhotra and Theodore W. Bremner

Publication: Special Publication

Volume: 163


Appears on pages(s): 1-52

Keywords: air-entraining cements; blast furnace slag; compressive strength; concretes; fly ash; freeze thaw durability; lightweight concretes; superplasticizers; underwater structures; water-reducing agents; wetting and drying tests; Material Research

Date: 8/1/1996

This paper deals with CANMET investigations on the performance of concrete, with and without supplementary cementing materials, in a marine environment. A series of more than 250 concrete prisms, 305 x 305 x 915 mm in size, were cast over a period of 16 years and installed at Treat Island, Maine, an outdoor exposure facility operated by the U. S. Army Corps of Engineers, U. S. A. The prisms of the first phase of the investigation were installed at the site in 1978, with the remaining specimens being installed at almost yearly intervals. The specimens of the latest phase were installed in 1994. The test prisms are installed at mid-tide level on a rack and are exposed to repeated cycles of wetting and drying and to about 100 cycles of freezing and thawing per year. The test specimens will be kept at the exposure site until at least the year 2005. The test prisms are evaluated annually. The evaluation includes visual examination and rating and ultrasonic pulse velocity testing. Also, a complete photographic record is kept. Some of the principal conclusions based upon up to 17 years of exposure of some of the test prisms are as follows. The use of non air-entrained concrete is not recommended for the exposure conditions experienced at Treat Island. For the exposure conditions experienced at Treat Island, the percentage of silica fume in concrete should be limited to 10 percent. Both the normal weight and semi-lightweight concretes incorporating fly ash or slag or silica fume or a combination of these materials are in good to excellent condition, provided water-to- cementitious materials ratio is kept below 0.50 and portland cement is kept at a certain minimum level. There is no significant difference in the performance of concrete made with ASTM Types I, II, and V cements.