Comparison of fly ash and rice husk ash effects on the mechanical properties of roller compacted concrete for pavements

Laboratory investigation was conducted focused on the utilisation of waste materials comprising Class F fly ash (FA) and rice husk ash (RHA), in roller compacted concrete (RCC) for pavement applications. The mixtures of RCC comprised CEM I 52.5 N Portland cement containing 0%, 5%, 10%, 20% and 30% wt FA or RHA. Various aggregate characteristics were measured to determine their suitability for road applications. Compaction tests were done to obtain values of optimum moisture content for RCC mixtures. The mechanical properties investigated comprised compressive strength, static modulus of elasticity, dynamic modulus of elasticity and ultrasonic pulse velocity. Results showed that proportions of up to 5–10% wt RHA or FA were optimal and can be recommended for incorporation in RCC pavement mixtures. Standard models giving the relationships between compressive strength, static and dynamic elastic moduli of normal concretes, were found to be also applicable to RCCs.