The rapid expansion of ceramic wastes in China has raised great many interests in their sustainable uses in building materials. This work reports a type of micro ceramic powder with the mean size down to ∼3.5 μm manufactured from ceramic wastes toward developing sustainable building materials. The micro ceramic powder was taken as a supplementary cementitious material to replace cement up to 40% for tuning the microstructure and mechanical properties of blend cement materials. Microscopic and macroscopic tests were conducted on the materials up to 180 curing days. Results indicate that the ultimate compressive strength of the blend mortars is over 80 MPa, and the bending strength is around 10 MPa. The filling and pozzolanic effects of micro ceramic grains increase the meso porosity (≤ 50 nm) and decrease the threshold pore size. The pozzolanic reactions between ceramic grains and calcium hydroxides form complex calcium-silicate-alumina-hydrates with the Ca/Si ratio around 1. The hybrid reactions of cement and ceramic grains increase the non-evaporable water but decrease the calcium hydroxide. Estimations suggest that 20% replacement of cement by the micro ceramic powder indicates an economical benefit of 9.6% in concrete manufacture and a decrease of 6.62% specific energy consumption in cement production. This work addresses the interactions between micro ceramic grains and cement hydrates for the sustainable uses of ceramic wastes in building materials. Display omitted •Micro ceramic powder was manufactured from ceramic wastes for partial cement replacement.•Waste ceramic powder refines the pore structure of cement materials.•Pozzolanic reaction enhanced the interactions between ceramic grains and cement matrix.•Waste ceramic powder enables a more sustainable concrete manufacture.