Effect of magnesium oxychloride cement on stabilization/solidification of sewage sludge

Solidification/stabilization (S/S) is considered to be a well-established disposal technique to reduce sludge handling and disposal obstacles. In this work, the sewage sludge was solidified at variable proportions with magnesium oxychloride cement (denoted as MOC thereinafter) as reagent. The mortar prism samples of 40 × 40 × 160 mm in dimension were prepared and hardened for 24 h at room temperature. Unconfined compressive strength after 10-day curing time, initial and final setting time, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and toxicity leachability of the samples, were used to characterize the macroscopic and microscopic effects caused by the solidified products on the MOC hydration process. The results revealed that the magnesium hydration of phase 3, phase 5 and other hydration components in CS developed a crystallizing network in the hydrated solidified products, which not only enhanced the strength of CS but also prevented the precipitation of heavy metal ions from CS.