In the northwestern saline soils and coastal areas, cement soil (CS) materials are inevitably subjected to various factors including salt erosion, dry-wet cycle (DWC), temperature fluctuations and dynamic loading during its service life, which the coupling effect of these unfavourable factors seriously threatened the durability and engineering reliability of CS materials. Additionally, combined with the substantially extensive application prospects of rubber cementitious material, as a resource-efficient civil engineering material and fibre-reinforced composites, consequently, in order to address aforementioned issues, this investigation proposed to consider the incorporation of rubber particles composite basalt fiber (BF) to CS materials as an innovative engineering solution to effectively enhance the mechanical and durability properties of CS materials for prolonging its service life. In this study, sulphate ions were utilized to simulate external erosive environment and basalt fibre rubber cement soil (BFRCS) specimens were subjected to various DWC numbers (0, 1, 4, 7, 11 and 15) in diverse concentrations (0 g/L, 6 g/L and 18 g/L) of Na2SO4 solution, and specimens that had completed the corresponding DWC number were then conducted both unconfined and dynamic compressive strength tests simultaneously to analyze static and dynamic stress-strain curves, static and dynamic compressive strength, apparent morphological deterioration characteristics and energy absorption properties of BFRCS specimens. Furthermore, further qualitative and quantitative damage assessments of pore distribution and microscopic morphology of BFRCS specimens under various DWC sulphate erosion environments were carried out from the fine and microscopic perspectives through pore structure test and scanning electron microscopy (SEM) test, respectively. The test results indicated that the static, dynamic compressive strength and specific energy absorption (SEA) of BFRCS specimens exhibited a slight increase followed by a progressive decline as DWC number increased. Additionally, compared to 4 mm BFRCS specimens, those with 0.106 mm rubber particle size demonstrated more favorable resistance to DWC sulphate erosion. The air content, bubble spacing coefficient and average bubble chord length of BFRCS specimens all progressively grew as DWC number increased, while the specific surface area of pores gradually decreased. The effective combination of BF with CS matrix significantly diminished pores and weak areas within specimen, and its synergistic interaction with rubber particles efficiently mitigated the stresses associated with expansive, contraction, crystallization and osmosis subjected by specimen. Simultaneously, more ettringite (AFt) had been observed within BFRCS specimens in 18 g/L sulphate erosive environments. These findings will facilitate the design and construction of CS subgrade engineering in northwestern saline soils and coastal regions, promoting sustainable and durable solutions while reducing the detrimental environmental impact of waste rubber.

The escalating environmental challenges posed by waste rubber tyres (WRTs) necessitate innovative solutions to address their detrimental effects on the geoenvironment. Thus, the knowledge about the recent advancements in material recovery from WRTs, emphasising their utilisation within the framework of the United Nations Sustainable Development Goals (SDGs) and the circular economy principles, is the need of the hour. Keeping this in mind, various techniques generally used for material recovery, viz., ambient, cryogenic, waterjet, and so on, which unveil innovative approaches to reclaiming valuable resources (viz., recycled rubber, textiles, steel wires, etc.) from WRTs and various devulcanisation techniques (viz., physical, chemical, and microbial) are elaborated in this paper. In parallel, the paper explores the utilisation of the WRTs and recovered materials, highlighting their application in geotechnical and geoenvironmental engineering development projects while addressing the necessary environmental precautions and associated environmental risks/concerns. This paper incorporates circular economy principles into WRTs utilisation and focuses on achieving SDGs by promoting resource efficiency and minimising their environmental impact.

This paper presents laboratory and field test results on the use of tire cell track foundation (TCTF) consisting of an assembly of infilled rubber tires to reinforce capping material below the ballast layer. Large-scale cubical triaxial tests were carried out with two different infill materials (crushed basalt rockfill and recycled spent ballast) and they were subjected to varying cyclic loading magnitudes and frequencies. A multistage cyclic loading was performed with and without the inclusion of tire cell reinforcement, whereby the cyclic loading was applied in four different stages with 25,000 loading cycles in each stage. In the first two stages, the frequency was increased from 10 to 15 Hz for an equivalent axle load of 25 t. For the third stage, the axle loading was increased to 35 t with a frequency of 10 Hz, which was then increased to 15 Hz in the final stage. The results showed that the TCTF could reduce the vertical stress transmitted to the subgrade layer as well as curtail the vertical and lateral displacement of the ballast layer. The TCTF further stabilized the track without any significant reduction of the resilient modulus of the overlying ballast as the loading and frequency increased. Compared to a traditional track, the TCTF showed a reduction of 40.1% and 28.3% in the breakage index for the crushed latite basalt and spent ballast (i.e., recycled from ballast tips) infilling the tire cells, respectively. Test results confirm that the TCTF can significantly improve the overall track performance, and this could be mainly attributed to the increased confining pressure provided by the tire cell assembly, as well as the enhanced damping properties of the rubber tire inclusions. In addition, the concept of TCTF was tested using a fully instrumented track (20 m long) subjected to the passage of a 22-t locomotive with two fully loaded carriages. The trial was constructed within a maintenance yard for heavy haul rolling stock located in a western suburb of Sydney, Australia. Field measurements revealed that, compared to the standard track, the TCTF significantly reduces stress transfer to the subgrade soil. This ultimately mitigates excessive deformation and subgrade failure, making TCTF a sustainable solution for soft and weak subgrade soils despite initial settlement.

Owing to the order of the day, we are searching for an ecofriendly binding ingredient instead of cement, which is now universally used in concrete. Almost everyone extensively exploits construction materials due to their good durability and compressive characteristics. The present study examines the use of Acacia nilotica ash as a cement substitute. It is known that Acacia nilotica`s aggressive roots are extremely presumptuous and invasive and spoil the foundation of buildings. By gripping water from adjoining areas, they change soil nitrogen and are a major source of affecting plant growth. In this work, the M 35- grade geocomposite was investigated by incorporating Acacia nilotica ash at 0%, 2.5, 5%, 7.5%, 10%, 12.5%, and 15% for fly ash. Mechanical and durability studies were carried out by changing the magnitude of Acacia nilotica ash and evaluating it with the standard composite samples.