The sustainable development of human society makes necessary the research on and the use of RAC. For the purpose of enlarging its application range, both lowering cost and enhancing properties of RCA are worth being done. This paper aims at improving RAC’s resistance to permeability and freeze-thaw with a lower addition amount of calcined diatomite compared with silicon fume. Therefore, the main study on effects of calcined diatomite on resistance to permeability and freeze-thaw is carried out through comparison experiments. Research results indicate that the calcined diatomite of 2% added is able to decrease relative penetration coefficient by 59%, the strength loss by 4.9% and the relative strength loss by 3.3%. Obviously, the lower addition of calcined diatomite could achieve good effects, which arrived at the goal of this paper.