Partial replacement of cement with port dredging waste in the production of coating mortars

The accelerated expansion of the cement industry, driven by the growing housing demand in urban centers, has resulted in increased consumption of raw materials and elevated carbon dioxide (CO₂) emissions. Simultaneously, the disposal of dredged material from ports and navigation channels presents an environmental concern, as improper management can significantly harm marine ecosystems. This study investigates the use of port dredging waste (PDW) as a supplementary cementitious material in coating mortars acting as a filler material, promoting packing and nucleation. Two types of cement were used: Ordinary Portland Cement (OPC) and Calcium Sulfoaluminate Cement (CSA), with PDW partially replacing cement at 10%, 30%, and 50% in mass, along with a control mix without replacement. The experimental program included evaluations of fresh and hardened properties, such as consistency (flow table and plunger tests), bulk density, entrained air content, water retention, flow, hydration kinetics by isothermal calorimetry, capillary water absorption, compressive and tensile strength, adhesion to substrates, and durability under wet-dry cycles. Characterization of the PDW indicated that it is appropriate for use as a filler material in coating mortars. In the fresh state, the incorporation of PDW reduced workability due to increased water demand, as observed in consistency tests. In the hardened state, replacing 10% of OPC with PDW improved compressive strength from 4.06 to 4.59 MPa and tensile strength from 0.3461 to 0.5796 MPa. In contrast, CSA-based mixtures showed reduced mechanical performance and durability as PDW content increased. These results suggest that 10% PDW replacement in OPC-based mortars is a viable and sustainable alternative, while further research is needed to address technical challenges in CSA-based systems. Practically, the use of PDW in OPC mortars offers an environmentally friendly strategy to reduce cement consumption, valorize dredged materials, and enhance the sustainability of construction coatings.