Selective Use of Fly Ash Concrete

Structural grade fly ash (FA) concrete and concrete with high volume of fly ash (HVFA) are well accepted and utilized in the Australian construction industry. These are concretes with fly ash (ASTM C 618 type F) making up between 10 and 50% by weight of the total cementitious material. This paper is intended to demonstrate the importance of the selection of the appropriate amount of FA content for a range of applications. The durability performance of the FA concretes was compared with portland cement concretes of equivalent 28-day compressive strength, in terms of the resistance to carbonation, chloride penetration and sulfate attack. Some mixture design data for both FA and HVFA concretes and their mechanical properties are given. The likely optimum fly ash percentages for a range of applications are highlighted with respect to their properties and construction demands. It was found that a lower fly ash dosage would be more suitable for above ground structures where a carbonation-related deterioration mechanism applied. However, for structures in aggressive sulfate ground condition or in marine environments, HVFA concrete was found to be much more suitable. Available field performance data have confirmed laboratory evaluated performance.