A new approach to improving the water resistance of MOC-solidified sludge using [formula omitted] ions

Abstract

With the growing sustainability concerns and awareness of environmental conservation, utilizing magnesium-based cement in construction has garnered considerable attention in recent years. In this work, a novel and sustainable approach to treating sludge has been developed by incorporating NaHCO3 to enhance the properties of MOC (Magnesium Oxychloride Cement)-solidified sludge. Different properties were determined through various experimental techniques, such as unconfined compressive strength (UCS), durability, scanning electron microscopy (SEM), X-ray diffraction (XRD) tests, and mercury intrusion porosimetry (MIP) to assess the impact of NaHCO3 content, curing age, and other factors on the strength, water resistance, microstructure, and reaction products of MOC-solidified sludge. The results indicate that adding NaHCO3 significantly enhanced the compressive strength and water resistance of MOC-solidified sludge, with an optimum NaHCO3 content of 50%. However, excessive NaHCO3 content led to a reduced MOC content, as evidenced by a strength loss rate of approximately 50% when NaHCO3 content reached 200%. Adding NaHCO3 also produces hydrated magnesium carbonates in solidified sludge in addition to Phase 5 and Brucite (Mg(OH)2). The expansion and cementation properties of these reaction products effectively filled the pores of the samples, facilitating the bonding of soil particles, establishing a stable spatial network structure, and improving the resulting strength of MOC-solidified sludge.