Recovery of field samples provides unique information about the strength and the long-term functionality of deep stabilized soil in actual transportation infrastructures. This paper presents the results of uniaxial compressive tests for the stabilized field samples of two railway sites and one street site located in Finland. Based on the research findings, there is considerable variation in the shear strength of the field samples, with coefficients of variation (COV) ranging from 0.12 to 0.61. However, the average strengths across all sites achieved their target values set during design. The results demonstrate a significant increase in strength over time, especially at the older research sites. In a railway site where deep stabilization was performed 3.5 years ago, the average shear strength of the stabilization was 797 kPa, which is more than seven times greater than the target strength for the stabilized columns. The relationships between shear strength and deformation ratios for the columns and soil surrounding the columns exceed the assumed ratio values presented in the guidelines of Finnish Transport Infrastructure Agency (FTIA), which present a value of less than 20 for completed stabilization. Based on the results of all sites, the deformation ratio between columns and clay was found to be as much as 101. This result implies that the stress concentrates more on the columns than assumed in the FTIA's guidelines. Nevertheless, the structures have performed well without any visible differences in settlement or other damages.

Hazardous alkylphenol wastes (HAPW) are a class of organic semisolid waste characterized by large production, complex composition and difficulties associated with recycling. Their generation and disposal lead to significantly environmental issues, including water and soil pollution, and present a substantial industrial challenge. To address these issues, a sustainable, low-carbon strategy for the high-value utilization of HAPW has been proposed. We take HAPW as a compatibilizer in the production of epoxy asphalt for road construction materials. Experimental results show that the HAPW-based epoxy asphalt containing 19.5 wt% HAPW exhibited optimal mechanical properties (tensile strength: 4.16 MPa; elongation at break: 164.92 %), exceeding industrial standards and outperforming epoxy asphalt produced using commercial cardanol through conventional processes. With a detailed molecular dynamics simulation, it is found that the HAPW plays two key roles in enhancing the interactions between epoxy resins and asphalt: (i) HAPW generates numerous hydrogen bonds with both asphalt and epoxy resin phases, strengthening noncovalent interactions and improving interfacial miscibility between the two phases. (ii) HAPW could react with the epoxy resin through the phenolic hydroxyl group, which further improves the interactions between epoxy resin and asphalt. This approach facilitates the treatment of hazardous organic waste in an environmentally sustainable and low-carbon way, enabling the recovery and repurposing of organic waste into high-valued products. Consequently, it promotes the resource utilization of industrial wastes while simultaneously contributing to a reduction in carbon emissions.

Excavated soil from widescale tunneling and excavation can be used in 3D-printed constructions. This research investigates the feasibility of 3D printing using geopolymer stabilized excavated soil (GP-E) containing 42% clay rich in kaolinite minerals. At dosages 0.50-1.5 wt%, sucrose is added to control the hydration and timedependent rheological properties, enabling adequate open printing time (OPT) for large-scale printing. Experimental findings show that 1% and 1.5% sucrose addition to GP-E offers OPT of 130 min and 170 min respectively compared to 32 min for GP-E. By enabling better dispersion, the addition of sucrose allows smooth extrusion with shape retention of 90 - 92% at a lower NaOH solution-to-binder ratio (0.68) than GP-E (0.75). Sucrose and clay (in the soil) act synergistically to reduce the time-dependent static yield stress but maintain it at an adequate level of 5-8 kPa required for stacking up the layers without collapse. Flow retention and thixotropy are maintained at 100% during the printing window, which balances extrusion and buildability. As a result, the sucroseGP-E mix could be built up to a height of 1.05 m compared to 0.19 m for GP-E. 1 % sucrose-added GP-E possesses 28 - 40% and 70% higher wet compressive strength and inter-layer bonding respectively compared to GP-E depending on the loading direction. These are linked to the refinement of capillary porosity and a 13-15% reduction in shrinkage. In summary, the findings present a potential route for controlling the printing time of geopolymer-stabilized earthen materials while reducing the embodied carbon and enhancing the mechanical performance.

The dumping of titanium slag (TS) and fly ash (FA) could lead to the occupancy of abundant land resources and the pollution of air, soil and underground water. The meso-regulatory function of the lightweight and thermally stable porous TS makes it a feasible material as the fire-resistive cementitious composites (FRCCs). This paper proposed a novel low-carbon FRCC with favorable high-temperature resistance by using TS and FA. Then, the mechanical properties and mechanism improving the heat resistance were systematically studied. The results revealed that the addition of TS with proper quantity decreases the mass loss by 19.6% and degradation degree of mechanical strength by 31.8% after 800 degrees C heating. The thermally stable perovskite and akermanite phases in TS are conducive to improving the stability of mineral phases during high-temperature heating. Meanwhile, the porous structure of TS enhances the thermal insulation of FRCC, which postponed the mineral phase decomposition. In addition, the secondary hydration effect of FA consumes a large amount of Ca(OH)2, which effectively weakens the deterioration caused by the decomposition of Ca(OH)2 after 600 degrees C heating. Based on the CT results, the variations of internal pore structure including pore distribution, porosity, and fractal dimensions, were systematically analyzed. It is found that the TS particles can effectively optimize the internal pore distribution and limit the generation and deterioration of macro-pores. Moreover, the thermal damage model of the prepared FRCC was established by combining the pore structure deterioration degree and residual mechanical strength. Finally, compared with traditional fire-resistive fillers, the low carbon emission of the prepared FRCC was verified.