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In this paper, the preparation of calcium oxide (CaO) nanoparticles (NPs) is reported by a precipitation method, using CaCl2 and NaOH as starting raw materials. The produced NPs were characterized for chemical composition, phase composition, particle size distribution, morphological features, specific surface area, and crystallite sizes. It is shown that calcination of Ca(OH)2 in vacuum takes place faster/at a lower temperature compared to the calcination in air due to the higher entropy of the gaseous product of calcination. It is also shown that when these CaO nanoparticles are kept at room temperature in air, they fully and spontaneously transform into CaCO3 within 3 weeks. Therefore, if this material is disposed in open fields (not necessarily in industrial conditions), it is able to capture carbon dioxide from normal air slowly, but surely. However, when the CaO nanoparticles are kept in the air at 100–200 °C, they mostly capture water vapor from the air instead of carbon dioxide, and the resulting calcium hydroxide blocks the carbon dioxide capture by CaO nanoparticles.

The aim of this study was to investigate the construction and demolition waste (CDW) fine size fraction by increasing its reactivity with mechanical activation (MA) in a stirred media mill. Systematic measurements were carried out in order to gain information about its reactivity. Particle size distribution and BET specific surface area measurements were carried out as dispersion properties. The changes in the particle shape and surface were measured by scanning electron microscopy (SEM), and structural alteration was investigated by FTIR spectroscopy and X-ray diffraction (XRD). The effect of MA on the pozzolanic reactivity was measured by lime sorption as well as strength tests. As a result of the research, it was found that reactivity of the construction and demolition waste (CDW) fine size fraction could be controlled by MA in a stirred media mill.