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[Display omitted] • Marine sand was used to prepare foamed lightweight soil (MS-FLS). • Increased MS content decreased mechanical properties and durability of MS-FLS. • Increased shell content decreased the compressive strength and durability of MS-FLS. • Increased chloride ion content improved the sulfate resistance of MS-FLS. • MS-FLS mixtures are applicable in embankment engineering (>0.3 MPa) Mixing foamed lightweight soil (FLS) with marine sand (MS) can be a sustainable approach for maximizing waste resources, although the fundamental properties (the physical performance, durability, and microstructural behaviors) of MS-mixed FLS (MS–FLS) have not been investigated, and this significantly restricts its engineering application. Thus, in this study, macroscopic and microscopic experiments are conducted to comprehensively explore the properties of MS–FLS with different MS, chloride (Cl−), and shell contents. The results of the macroscopic tests reveal that MS–FLS exhibits a fluidity of 160–229 mm, a volumetric water-absorption rate of 13.1 %–19.5 %, and an unconfined compressive strength (UCS) of 0.95–2.64 MPa. Further, the flow of bubbles is promoted as the fluidity and water-absorption rate change, thus accumulating the bubbles with relatively large pore sizes and causing an increase in the overall relative pore size. Although the durability is reduced to varying degrees via wet cycling, freeze–thaw cycling, sulfate (SO2 − 4) erosion, and long-term outdoor exposure, most of the UCS values can still satisfy the requirement for subgrade engineering applications. Moreover, the microscopic tests indicate that the pore size increases with the increasing MS content, whereas the pore-wall thickness, cement density, mechanical properties, and durability decrease. As the shell content increases, the UCS and durability decrease considerably owing to the smooth, surface-induced weak points and low water-absorption capacity of the shells; however, the UCS can still satisfy engineering requirements. Finally, the increased Cl− content can improve the SO2 − 4 resistance due to the generated Friedel's salt, which fills the micropores in cement-hydration products, and this facilitates strengthening. Therefore, the UCS values of most MS–FLS specimens are > 0.3 MPa before and after the durability tests, revealing their promise for subgrade engineering applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • A comprehensive evaluation of engineering performance for TS-FLS is scarce. • Macroscopic physical properties and microscopic structure are analyzed. • Compressive strength and durability decrease with the increasing TS content. • Most TS-FLS mixtures are applicable in subgrade engineering (>0.3 MPa) • TS-FLS is an environmentally sustainable alternative in embankment engineering. Making lightweight soil with bubbles from raw soil and cement, i.e., foamed lightweight soil (FLS), is an environmentally sustainable way to utilize tailings sand (TS) as a replacement of cement in embankment applications, enlightened by its excess strength. However, a comprehensive evaluation of its engineering performance is needed. Thus, this study develops a foamed lightweight soil amended with tailings sand (TS-FLS) and explores its physical and mechanical properties, durability, and microscopic properties. The results reveal that the fluidity, volumetric water absorption, and compressive strength of TS-FLS mixtures are within 164–182 mm, 13.3–16.0 %, and 0.76–1.74 MPa, which could satisfy the requirement of the embankment applications. After dry-wet cycles, freeze–thaw cycles, sulfate erosion, and long-term outdoor exposure, most compressive strength is applicable in the application of embankment (>0.3 MPa). Note that the strength and durability show a decreasing trend with the TS content, and the critical content is less than 50 %. Besides, the increasing TS content shifts the failure mode from brittle to ductile (33 % and 40 %), which is favorable for engineering applications, while overused content (50 %) decreases the ductile response. The microstructure observation indicates that the TS increases the pore diameter size and worsens its uniformity, making the walls more vulnerable to compression rupture by stress concentration, thereby increasing water absorption. Moreover, a large number of crystals (i.e., secondary gypsum and ettringite) are generated under sulfate solution, making mechanical properties either improved by void-filling or damaged by microstructure-destroying. Therefore, TS-FLS is promising for embankment applications when an appropriate TS content is chosen. [ABSTRACT FROM AUTHOR]