Development of Sustainable Mortars and Concrete with Marine Sediment, Sea Sand and Seawater: A Review on Cement Hydration, Mechanical Strength, and Durability

Concrete production consumes vast quantities of natural aggregate and potable water, while coastal dredging produces hundreds of millions of cubic meters of underutilized marine sediments and sea sand annually. This study aims to provide a review on recycling dredged marine sediments, sea sand, and seawater into sustainable mortars and concrete. Systematically synthesizing the investigations on cement hydration kinetics, phase transformations, fresh-state workability, mechanical strength evolution, and long-term durability mechanisms under aggressive marine exposure. The studies revealed that chlorides and sulphates in seawater and unwashed marine sands accelerate early hydration kinetics, advancing exothermic heat flow peaks by 1.2 to 1.7 h and boosting early compressive strength by up to 53%. However, this rapid early reaction leads to long-term trade-offs, including nearly doubled drying shrinkage, increased scaling during salt-frost cycling, and elevated corrosion vulnerability for steel reinforcement. Furthermore, dredged sediments cause substantial workability loss and strength deterioration beyond a threshold value as clinker or fine aggregate replacement, primarily due to clay water absorption and dilution effects. Thermal calcination (650–850 °C) and washing pretreatments, combined with supplementary cementitious materials (supplementary cementitious materials, SCMs, like ground granulated blast-furnace slag, fly ash, and metakaolin), effectively mitigate these adverse effects by consuming Portlandite, stabilizing Friedel’s salt, and refining pore tortuosity. An application-oriented utilization framework is established: fine clayey sediments are best suited as calcined SCMs at a 5–15% replacement, washed sand fractions serve structural applications up to 30%, and stabilized bulk sediments are ideal for non-structural masonry and sub-bases at 40–70%. These insights provide concrete guidelines for safely adopting marine-derived resources, diverting harbor waste from landfills, and advancing resource circularity in coastal civil infrastructure.