Book Description
This paper describes the development of high volume fly ash (HVFA) concrete for structural concrete and pavements. Trials carried out at Pacific Power's Mount Piper Power Station project in New South Wales is also described. Concretes with high fly ash content (40% and above by weight of the total binder fractions) were designed for structural grades. The workability, mechanical and long-term volume stability properties were evaluated. It was found that HVFA concrete could be designed having fresh concrete properties similar to plain cement concrete with the exception of setting times. HVFA concretes with characteristic compressive strength up to 5O MPa could be produced. For concretes of similar strength grades, it was found that the flexural strength and elastic modulus properties of HVFA concretes were similar to plain cement concretes. HVFA concretes were found to have similar or lower drying shrinkage at 56 days when compared to companion plain cement concretes of equivalent grades. Creep strains were also improved significantly in HVFA concretes. The setting times were increased by one to SLY hours depending on the type of cement and percentage of fly ash used. The concretes also developed considerable strength after 24 hours to withstand loading from normal construction activities. Trial production and placing of these concretes for apron slabs and road pavements was carried out at the Pacific Power's Mount Piper Power Station. It was found that HVFA concrete could be produced and placed successfully through normal concreting practices including pumping. A 5 to 6% air content could also be entrained with normal air entraining agent. The finished pavement looked similar to that placed using conventional concrete. While severe retardation in setting was found in the last two trials, it was subsequently found that it was caused by the incompatibility between the water reducing agent and the binder system. Long-term performance of these concretes are being monitored.