A review on the utilization of dredged sludge as a promising low-carbon supplementary cementitious material: activation, properties and microstructure

This paper provides a comprehensive review of the activation potential of dredged sludge (DS) and the latest research progress in preparing low-carbon cementitious materials using it. It is found that DS, as a solid waste rich in silico-aluminates, can enhance its pozzolanic activity through physical, chemical and microbial activations. By optimizing the activation process and incorporating industrial by-products, the compressive strength and elastic modulus of hardened paste containing 5 ∼ 40% activated sludge ash (ASA) can be effectively enhanced, even surpassing those of pure cement paste. Moreover, it exhibits good compatibility in alkali-activated materials, magnesium phosphate cement, and magnesium oxychloride cement. Microscopically, ASA optimizes the pore structure of cement paste and enhances its resistance to ion erosion and the immobilization of heavy metals due to its pozzolanic activity and the additional release of reactive aluminum. The future will overcome the challenges of its multi-source heterogeneity and high costs of large-scale application. • Components and heavy metal distribution of sludge from various regions were counted. • Activation effects of sludge under different methods were evaluated. • Basic properties of sludge-based cementitious materials were summarized. • Microstructural features of sludge-based cementitious materials were revealed. • Challenges and prospects of sludge use in building materials were analyzed.