Evaluation of Indian fly ashes for the HVFA concrete, Part Ⅱ: Behaviour in concrete

摘要

In 2001, a number of fly ash samples and two cement samples were sent from India for testing at CANMET, Canada. These samples were characterised and concrete mixtures were made and tested with each fly ash sample. The characterisation studies showed that almost all of the Indian fly ashes are suitable for use in the high-volume fly ash (HVFA) concrete system. The results obtained in the laboratory investigation indicated excellent strength development of concretes made with the reference Canadian cement and the Indian fly ashes. The concrete made with the cement and fly ash, both from India, appeared to experience a setting delay, and showed a lower, yet acceptable one-day strength. However, the strength gain of this concrete with age was very rapid, leading to one of the higher strengths measured at 91 days. The chloride-ion penetration of the concretes at 91 days was found to be in the range of 200 to 800 coulombs. The compatibility of the Indian cements and the admixtures used, as well as the workability aspects of some fly ashes need further investigation. In general, all the Indian fly ashes performed well in terms of strength and chloride-ion penetrability in this limited investigation.