Abstract
Recycled aggregates should be used much more than ever for the promotion of effective utilization of limited resources. Therefore, it is very important to propose the proper methods for the application of recycled aggregates to concrete. The goal of this research is to establish the concrete mix design containing both low quality recycled coarse aggregate and carbon-free fly ash（here in after referred to as CfFA）with loss on ignition as low as 1.0％ or less. In this paper, the fundamental data on fresh and hardened properties of the recycled concrete are investigated and discussed in detail. As a result, in case of mixing CfFA, the flowability of the recycled concrete is improved, and the drying shrinkage strain is reduced by 4-8％ on the average. Regarding the compressive strength, the 28-day strength equation of base concrete made with normal aggregate can be applied to that of recycled aggregate, by introducing the amount of the increase in absorption between normal and recycled aggregate（⊿W）, and a cementing efficiency factor（k）due to pozzolanicity of fly ash. The effects of the use of recycled aggregate on drying shrinkage strain of concrete can be also explained by the apparent water content（W´＝W＋⊿W）. The carbonation depth is influenced by the water-cement ratio regardless of the kinds of aggregate and using CfFA.
