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a. Introduction      b.Effects on Fresh Properties     c. Effect on Hardening Properties    d. Production
e. Applications That Make Best Use of Fly Ash in Portland Cement Concrete

 e. Applications That Make Best Use of Fly Ash in Portland Cement Concrete

i. Reinforced Concrete with enhanced Resistance to Steel Corrosion Due to Chloride Ingress
  The enhanced resistance to chloride ion penetration makes fly ash concrete a viable corrosion-protection strategy for reinforced concrete structures exposed to chlorides. Such structures include highway structures exposed to deicing salts, buried structures such as tunnels that are exposed to saline groundwater, and marine structures.

         

ii. Containment of Hazardous Wastes Using Very Impermeable Concrete
  The low permeability of fly ash concrete can be advantageous for containment of hazardous wastes.

iii. Control of Alkali-Silica Reaction (ASR)
  Low-calcium fly ash is a viable strategy for controlling expansion due to ASR in concrete structures containing reactive aggregates. A good example of such use is the Lower Notch Dam in Ontario. This structure was built around 1970 using a reactive aggregate and a high-alkali cement with 20 to 30% of the cement being replaced with a Class F fly ash. Many structures in the same location built with the same aggregate are suffering deterioration due to ASR, but the Lower Notch Dam is in excellent condition after more than 30 years service.

Structures without Fly Ash

         

Lower Notch Dam Same Aggregate (as other structures) but with 20~30% Class F Fly Ash

        

iv. Sulfate Resistance
  Low-calcium fly ash can be combined with ordinary Portland cement to provide equivalent performance to sulfate-resistant Portland cement for use in aggressive sulfate-bearing soils or groundwaters.

         

v. Low heat of Hydration
  Low-calcium fly ash can be combined with ordinary Portland cement to provide equivalent performance to low-heat Portland cement for use in massive sections where temperature rises due to cement hydration have to be controlled. The first major use of fly ash in concrete – the construction of the Hungry Horse Dam in the U.S.A. – was for this reason. Fly ash is now commonly used in mass foundations and water-retaining dams for temperature control.

         

vi. Where enhanced economy and ease of placement are needed
  In most applications where no special property is required, fly ash may be used solely for reasons of economy or improved placement.

         
       

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