Effect of catalyst in wet carbonation process for recycled cement paste powder

Wet carbonation is a feasible approach to convert recycled cement paste powder (RCP) derived from concrete waste into value-added products. To investigate the effect of catalysts on wet carbonation efficiency, this paper utilized 5 types of chemicals including triethanolamine (TEA), ethanol, glycerol, ethylenediamine (EDA) and 1,3-diaminopropan (DAP). A series of experiments and analysis were conducted including Fourier-transform infrared spectroscopy (FTIR), X-ray fluorescence spectroscopy (XRF), X-ray powder diffraction (XRD), and thermogravimetric analysis (TGA). The results showed that i) the optimal dosage of catalysts ranged from 0.1-1 wt%; ii) the carbonation products shared similar chemical compositions using different types of catalysts; iii) the alkanolamine-group TEA which improved the production of Si-rich gel by 175.16-201.91% was preferred comparing with hydroxyl-group and amino-group; iv) TEA chelated Ca 2+ and Al 3+ from hydration products to form TEA-Ca 2+ complex and TEA-Al 3+ complex and enhanced the carbonation efficiency; v) the SiO 2 to Al 2 O 3 molar ratio of the coprecipitated gel was approximately 3: 1 and the aluminum gel served as a key factor for the precipitation of Si-rich gel. • The alkanolamine-group catalyst was preferred compared with hydroxyl-group and amino-group; • The SiO 2 to Al 2 O 3 molar ratio of the coprecipitated gel was approximately 3: 1; • The aluminum gel served as a key factor for the precipitation of Si-rich gel; • And the chemical compositions of the Si-rich gel was similar regardless of catalyst types.