High Volume Fly Ash RCC for Dams ― I: Mixture Optimization and Mechanical Properties

摘要

A series of roller-compacted concrete mixtures were developed for the Norwegian Skjerka hydropower project. The mixture optimization was based on the medium-paste concept of the International Committee On Large Dams (ICOLD) using crushed aggregate from the dam site. The mixture optimization consists of a two-step procedure minimizing the paste content, keeping the compacted density above 97.5% of the theoretical air-free density, and giving an optimal loaded Vebe time of 10 ― 20 seconds. Nine mixtures were produced using low calcium fly ash and portland cement with various fly ash-cement propotions. The water-binder ratio was kept constant at 0.53 according to the Norwegian code for mass concrete for dams. The laboratory test results showed that 8 of 9 binder combinations produced RCC within the design criteria. The compressive strength development of the water-cured specimens was impressive despite the rather low cement contents, giving 1 year strengths of 2 times the 28-day strengths. The use of high-volume fly ash concrete for RCC dams is one example of concrete in harmony with lower environmental impact and less use of resources.