Semidry Flue Gas Desulphurization Ash as Set Retarders in Portand Cement

The present study is focused on clarifying the influence of semidry flue gas desulfurization (SFGD) ash in replacing natural gypsum (NG) in the production of ordinary Portland cement (OPC). Clinker, 3 wt% of Slag and 6-12 wt% of modified SFGD ash were ground in a laboratory ball mill to produce cement. The properties of SFGD ash were investigated via chemical composition analysis, Scanning electron microscopy (SEM), X-ray Diffraction (XRD), and differential thermogravimetric analysis (TG-DTA). The mechanical properties of cement were tested in terms of the initial and final setting time, soundness, flexural strength and compressive strength of different hydration ages. The XRD results of SFGD ash revealed the ash mainly contains CaSO₃, CaSO₄, CaCO₃, Corundum and mullite. And the micrographs and structure of the hydration products formed in cement were investigated by SEM and XRD. The results indicated that modified SFGD ash can retard the setting time of cement. And the setting time, soundness, compressive strength and bending strength of cement have been up to national standards (GB175-2007, China).