New Method for Assessing Frost Damage in Non-Air Entrained Hydraulic Structures


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Title: New Method for Assessing Frost Damage in Non-Air Entrained Hydraulic Structures

Author(s): R. D. Hooton, J. A. sato, and P. K. Mukherjee

Publication: Special Publication

Volume: 131


Appears on pages(s): 339-356

Keywords: concretes; freeze-thaw durability; hydraulic structures; moisture; non-air-entrained concrete; tests; water; Materials Research

Date: 3/1/1992

One of the major problems with rehabilitation of frost damage in old non-air-entrained hydraulic structures is prevention of failure of the repaired surface at the new/old concrete interface or in the old substrate concrete below the repair due to trapped moisture and subsequent freezing of the critically saturated substrate. A survey of several 40- to 75-year-old, non-air-entrained concrete dams indicated that in many cases the concrete at the water line was not damaged due to freezing and thawing. This would appear to contradict conventional wisdom based on ASTM C 666 testing of non-air-entrained concrete. Instead, most of the deterioration had taken place on the inclined downstream faces of the gravity sections, away from direct exposure to water, but subject to many cycles of freezing in air. In some cases, water leaked through joints in the concrete and initiated progressive raveling. However, in other cases, it appeared that moisture was drawn to the exposed surfaces by capillary suction. As a result of these observations, it was decided to develop a one-sided freezing test, with the unfrozen side exposed to water and the freezing side exposed to air, to better simulate field exposure. The cylindrical concrete specimens are monitored with temperature, relative humidity, and moisture probes at various depths during testing. This should allow evaluation of non-air-entrained concrete and various repair materials on the freezing surface to observe whether moisture is building up to critically saturated levels that would result in deterioration. While the equipment for this test has been designed and built, testing is at a preliminary stage. Describes the nature of frost damage in hydraulic structures and then describes the new test procedure in detail.