Very high volume fly ash concrete utilising microash and hydrated lime, with silica fume

The incorporation of a high volume of fly ash (FA) (up to 80%) in concrete without compromising mechanical and durability properties is potentially very advantageous to the concrete industry in terms of economic, social and environmental benefits. The compressive strength, carbonation, chloride ion penetration, water absorption and permeability of two high-volume FA mix designs incorporating 80% class F ultrafine FA (known as microash) and hydrated lime, with and without the addition of silica fume (SF) were investigated in this study. The specimens were cured for a maximum of 90 days to optimise completion of the hydration reaction. The concrete containing with 80% microash exhibited compressive strength in excess of 40 MPa at 28 days and over 70 MPa at 90 days. The material also displayed excellent durability properties compared with normal Portland cement concrete and other high-volume FA concretes. The addition of SF (10%) further improved the strength and durability properties of the material.