Influence of gradation of five types of recycled aggregate on strength of recycled aggregate concrete was investigated.The experimental result shows that smaller nominal maximum size of recycled aggregate contributes to strength development.Grading range and key grain size of micro-powder system are proposed.And optimized gradation is calculated in situation of adding silica fume alone,incorporation of another mineral powder,or combination of silica fume,fly ash and blast slag.Addition of silica fume is essential to intense packing whereas addition of several mineral blendings together is more effective due to its more intense packing effect,which is verified by calculated packing density.When double mineral admixtures were used,rehological parameters were measured and the relatively lower yielding stress and plastic viscosity prove that an optimum gradation is acquired in case of 15%(by mass) silica fume and 15%(by mass) fly ash is added.
