Effect of Fly Ash on the Durability Properties of High Strength Concrete

TLDR

Fly ash as a supplementary cementitious material enhances concrete sustainability by lowering cement‑related CO₂ emissions and is known to improve durability, though the magnitude depends on fly ash characteristics. This study evaluates the durability of high‑strength concrete incorporating high‑volume Class F fly ash from Western Australia. Concrete mixes containing 30 % and 40 % fly ash were cast and tested for compressive strength, drying shrinkage, sorptivity, and rapid chloride permeability. The mixes achieved 28‑day compressive strengths of 65–85 MPa, and fly ash reduced drying shrinkage, sorptivity, and chloride ion permeation, thereby enhancing overall durability.

Abstract

Utilization of fly ash as a supplementary cementitious material adds sustainability to concrete by reducing the CO2 emission of cement production. The positive effects of fly ash as a partial replacement of cement on the durability of concrete are recognized through numerous researches; however, the extent of improvement depends on the properties of fly ash. In this study, durability properties of high strength concrete utilizing high volume Class F fly ash sourced from Western Australia have been investigated. Concrete mixtures with fly ash as 30% and 40% of total binder were used to cast the test specimens. The compressive strength, drying shrinkage, sorptivity and rapid chloride permeability of the fly ash and control concrete specimens were determined. The 28-day compressive strength of the concrete mixtures varied from 65 to 85 MPa. The fly ash concrete samples showed less drying shrinkage than the control concrete samples when designed for the same 28-day compressive strength of the control concrete. Inclusion of fly ash reduced sorptivity and chloride ion permeation significantly at 28 days and reduced further at 6 months. In general, incorporation of fly ash as partial replacement of cement improved the durability properties of concrete.