Fine powders from crushed waste concretes have high water absorption and their reuse is limited. In this research the fine powders with diameter of less than 4.75mm were activated by using grinding method and hydrothermal synthesis method, and then the specimens were manufactured from these activated fine powders by mechanically compacting at the pressure of 80MPa. The experimental results show that the instant maximum compressive strengths are 9.65MPa and 16.8MPa respectively for the specimens from the ground powders and the hydrothermal synthesis powders. Their apparent densities are low and they can be used as wall materials. The results also show that the optimal grinding time ranges from 80 min to 90 min when using the grinding activation method. When using hydrothermal synthesis method the proportion of lime as an admixture affects the compressive strength and the constant temperature period should be less than 7 hours as the temperature is 120 °Cfor the powder made from gravel concrete.