Kinetic characteristics of lightweight aggregates obtained from dredged sediment

This study employed two different dredged sediments with adding a little Na2CO3 and Al2O3 to prepare lightweight aggregates (LWA) through reasonable preheating and sintering. Physical, chemical and mechanical properties of LWA were measured, and microstructure and mineral phases were examined by means of scanning electron microscopy, energy-dispersive spectroscopy and X-ray diffractometry. The results showed that the basic properties of LWA meet the standards of China water treatment artificial ceramisite filter material. The porous LWA mainly consist of three mineral phases which were quartz, haematite and nepheline. A thermogravimetric with Coats–Redfern model fitting method was introduced to investigate lightweight aggregate matrix during sintering process, and the activation energy (E) and pre-exponential factor (A) were estimated. The results indicate that under different heating rates (5, 15, 20 and 40 K min−1) reaction models are different from each other in different stage, the E and A for these processes are in the range of 12.59 kJ mol−1 ~427.63 kJ mol−1, 2.23 s−1 ~9.13 × 1026 s−1, respectively, and 15 K min−1 was considered as an optimized heating rate.