Utilization of waste concrete powder as a substitution material for cement

This study is conducted to utilize waste concrete powder (WCP) made as a by-product manufacturing high quality recycled aggregate. The Blaine fineness of the WCP used was 928 and 1360 cm2/g. As the main characteristic of WCP, it is particle were angular similar to cement, and hydrated products were attached on the surface of particles. In addition, the particle size of WCP was larger than Ordinary Portland Cement (OPC) and in terms of chemical components it had higher SiO2 content. The viscosity of pastes that contained WCP decreased by up to 62% compared to paste that only used OPC, and the final set time was delayed about 2 h. As substitution rates of WCP increased, the flow value decreased by 30% at the most according to the comparison with mortar that only used OPC. The compressive strength of mortar decreased by up to 73% as level of WCP increased and sorptivity coefficients increased by 70%. According to the test results, it is desirable to keep WCP replacement OPC to below 15%.

► Two types of WCPs with different blaine fineness were used.
► Viscosity and yield stress were reduced in the paste mixed with the WCP.
► The flow was reduced in the mortar mixed with the WCP.
► Sorptivity coefficients were increased in the mortar mixed with the WCP.
► Compressive strength was reduced in the mortar mixed with the WCP.