Title:
Deterioration of Lightweight Fly Ash Concrete Due to Gradual Cryogenic Frost Cycles
Author(s):
Kamal Henry Khayat
Publication:
Materials Journal
Volume:
88
Issue:
3
Appears on pages(s):
233-239
Keywords:
compressive strength; cryogenics; deterioration; dilatometers; freeze-thaw durability; fly ash; lightweight concretes; liquefied gases; microscopy; modulus of elasticity; splitting tensile strength; thermal expansion; Materials Research
DOI:
10.14359/1828
Date:
5/1/1991
Abstract:
While the mechanical properties of a high-strength lightweight concrete containing fly ash was shown to improve at cryogenic temperatures, its susceptibility to repetitive cryogenic frost cycles still needs to be evaluated. Longitudinal thermal strains of water-saturated and air-dried concretes were monitored between 65 and -250 F (18 and -157 C). Cumulative drops in compressive and splitting tensile strengths were measured after each of five gradual freeze-thaw cycles ranging from a high of 65 F (18 C) to two low temperatures of -40 F (-4 C) and -100 F (-73 C). This was done to evaluate the concrete's frost durability at liquified petroleum and natural gas temperatures, respectively. As expected, moist concrete exhibits larger dilation and residual strains than air-dried concrete. The coefficients of thermal length changes of the tested concrete can range from 4.5 x 10-6 F (2.5 x 10-6 C) to 6.6 x 10-6 F (3.7 x 10-6 C). The compressive strengths of both moist and air-dried concrete cycled five times to -40 F (-40 C) are virtually unchanged; however, maximum losses of 10 percent may result when the extreme freezing temperature drops to -100 F (-73 C). The splitting tensile strength of air-dried concrete cycled to either cryogenic temperature does not undergo any significant damage, whereas the splitting tensile strength of moist concrete may exhibit up to a 20 percent loss. This sharp drop in splitting tensile strength of moist concrete can be caused by debonding observed at the interface between aggregate and cement paste.