Blended binder based on Portland cement and recycled concrete powder
The article investigates the properties of recycled concrete powder obtained by mechanochemical activation of recycled screening waste with organic plasticizer in vibrating mill. The waste concrete powder was considered as a part of blended binder based on Portland cement. The optimal powder ratio in blended binder was 30% by weight of cement with the maintenance of the strength properties. The laser diffraction method, X-ray analysis and IR spectroscopy, as well as standard methods were used to estimate the properties of activated powder. The activation of recycled screening waste in 150 min with 0.5% plasticizer allowed us to achieve the specific surface area of the powder at the range of 457.5 cm2/g with content of fine-grained particles in the size of 0–10 µm (26.6%) and 0–20 µm (31.2%). It was estimated that the increase of powder ratio in blended binder reduces the standard consistency of the paste and extends the setting time of the binder. The optimal content of the powder was 30% by weight of cement with standard consistency of 24.6%. The compressive strength at the age of 2, 7 and 28 days was 24.3, 37.4 and 50.5 MPa respectively. The structure change of recycled screening waste particles by mechanical destruction and surface amorphization of initial crystalline phases was confirmed by XRD method and IR spectroscopy.