The present paper sets out a comparative analysis of carbon emission and economic benefit of different performance gradients solid waste based solidification material (SSM). The macro properties of SSM were the focus of systematic study, with the aim of gaining deeper insight into the response of the SSM to conditions such as freeze-thaw cycles, seawater erosion, dry-wet cycles and dry shrinkage. In order to facilitate this study, a range of analytical techniques were employed, including scanning electron microscopy (SEM), X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP). The findings indicate that, in comparison with cement, the carbon emissions of SSM (A1) are diminished by 77.7 %, amounting to 190 kg/t, the carbon-performance ratio (24.4 kg/ MPa), the cost-performance ratio (32.1RMB/MPa) and the carbon-cost ratio (0.76kg/RMB) are reduced by 86 %, 56 % and 68 % respectively. SSM demonstrated better performance in terms of freeze-thaw resistance, seawater erosion resistance and dry-wet resistance when compared to cement. The dry shrinkage value of SSM solidified soil was reduced by approximately 35 % at 40 days compared to cement solidified soil, due to compensatory shrinkage and a reduction in pores. In contrast to the relatively minor impact of seawater erosion and the moderate effects of the wet-dry cycle, freeze-thaw cycles have been shown to cause the most severe structural damage to the micro-structure of solidified soil. The conduction of durability tests resulted in increased porosity and the most probable aperture. The increase in pores and micro-structure leads to the attenuation of macroscopic mechanical properties of SSM solidified soil. The engineering application verified that with the content of SSM of 50 kg/m, 4.5 % and 3 %, the strength, bearing capacity and bending value of SSM modified soil were 1.9 MPa, 180 kPa and 158, respectively in deep mixing piles, shallow in-situ solidification, and roadbed modified soil field.

In this study, ground granulated blast-furnace slag (GGBS) and fly ash (FA) were used as binders, while NaOH (NH) and Na2SiO3 (NS) served as alkali activators. Seawater (SW) was used instead of freshwater (FW) to develop a SW-GGBS-FA geopolymer for solidifying sandy soils. Geopolymer mortar specimens were tested for unconfined compressive strength (UCS) after being curing at room temperature. The results showed that the early strength of the seawater group specimens increased slowly less than that of the freshwater group specimens, while the late strength was 1.16 times higher than that of the freshwater group specimens. Factors including seawater salinity (SS), the GGBS/FA ratio, curing agent (CA) content, and the NH/ NS ratio were examined in this experiment. The results showed that the strength of the specimens was higher for SS of 1.2 %, G90:F10, CA content of 15 %, activator content was 15 %, and NH: NS of 50:50. The pore structure of the mortar specimens was analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and computerized tomography (CT), revealing the mechanisms by which various factors influenced the microstructure. XRD indicated that SW-GGBS-FA geopolymer mortar newly produced Friedel salt and calcium silicate sulfate hydrate (C-S-S-H). The microstructures observed by CT and SEM showed that the pore radius of the seawater specimens was mainly less than 10 mu m, and the maximum crack length was 92.55 mu m. The pore radius of freshwater specimens was larger than that of seawater specimens, and the largest crack was 148.44 mu m, which confirmed that Friedel salt and C-S-S-H fill the pores and increase the UCS of the specimens.

Silt soil is widely distributed in coastal, river, and lacustrine sedimentary zones, characterized by high water content, low bearing capacity, high compressibility, and low permeability, representing a typical bulk solid waste. Studies have shown that cement and ground granulated blast furnace slag (GGBFS) can significantly enhance the strength and durability of stabilized silt. However, potential variations due to groundwater fluctuations, long-term loading, or environmental erosion require further validation. This study comprehensively evaluates cement-slag composite stabilized silt as a sustainable subgrade material through integrated laboratory and field investigations. Laboratory tests analyzed unconfined compressive strength (UCS), seawater erosion resistance, and drying shrinkage characteristics. Field validation involved constructing a test with embedded sensors to monitor dynamic responses under 50% overloaded truck traffic (simulating 16-33 months of service) and environmental variations. Results indicate that slag incorporation markedly improved the material's anti-shrinkage performance and short-term erosion resistance. Under coupled heavy traffic loads and natural temperature-humidity fluctuations, the material exhibited standard-compliant dynamic responses, with no observed global damage to the pavement structure or surface fatigue damage under equivalent 16-33-month loading. The research confirms the long-term stability of cement-slag stabilized silt as a subgrade material under complex environmental conditions.

Research on the performance of solidified soil in capillary water absorption seawater environments is necessary to reveal the durability under conditions such as above seawater level in coastal zones. Taking soda residue-ground granulated blast furnace slag-carbide slag (SR-GGBS-CS) and cement as marine soil solidifiers, the deterioration characteristics of solidified soil resulting from capillary seawater absorption were elucidated systematically through a series of tests including capillary water absorption, unconfined compressive strength, swelling, local strain, and crystallization. The microscopic mechanism was analysed through nuclear magnetic resonance and X-ray diffraction tests. The results showed that cement-solidified soil exhibited higher water absorption and faster swelling compared with SR-GGBS-CS solidified soil in the one-dimensional seawater absorption state. In the three-dimensional seawater absorption state, solidified soil with low GGBS dosage experienced a significant transition from vertical shrinkage to swelling during the capillary water absorption process, leading to a substantial decrease in strength after 7 days of crystallization. Cement-solidified soil displayed non-uniform and anisotropic swelling, along with the formation of more external salt crystals. Overall, the soil solidified with 25% SR, 10% GGBS, and 4% CS demonstrated robust resistance to capillary absorption deterioration in a seawater environment due to its minimal water absorption and swelling, uniform surface strain, weak salt crystallization, and limited strength deterioration caused by capillary water absorption.

Land reclamation from the sea is increasingly common in coastal areas in China as its urban population continues to grow and the construction of subways in these areas becomes an effective way to alleviate transportation problems. Earth pressure balance shield (EPBS) tunneling in reclaimed lands often faces the problem of seawater erosion which can significantly affect the effectiveness of soil conditioning. To investigate the impacts, in this work, the stratum adaptability of EPBS foaming agents in seawater environments was evaluated based on a series of laboratory tests. The Atterberg limits and vane shear tests were carried out to understand the evolution characteristics of mechanical properties of clay-rich soils soaked in seawater and then conditioned with foams. The results revealed that, for the same foaming agents, the liquid limit and plastic limit of soils soaked in seawater were lower than those in deionized water due to the thinning of bound water films adsorbed on the surface of soil particles. Similarly, soils soaked in seawater had lower shear strength. In addition, the results indicated that the foam volume (FV) produced by foaming agents using seawater as the solvent was slightly higher than that when using the deionized water due to the higher hydration capacity of inorganic salt cations in seawater compared with organic substances. It was also shown that seawater had negative effects on the half-life time (T1/2) and the dynamic viscosity (eta) of foaming agents due to the neutralization reaction between anions in the foaming agents and Na+ present in seawater. The test results also confirmed that 0.5 % of the tackifier (CMC) can alleviate the issue of thin foam films caused by seawater intrusion and improve the dynamic viscosity of foaming agents more effectively, leading to superior resistance to seawater intrusion in EPBS tunnel constructions.

Coastal regions often face challenges with the degradation of cementitious foundations that have endured prolonged exposure to corrosive ions and cyclic loading induced by environmental factors, such as typhoons, vehicular traffic vibrations, and the impact of waves. To address these issues, this study focused on incorporating Nano-magnesium oxide (Nano-MgO) into cemented soils to investigate its potential impact on the strength, durability, corrosion resistance, and corresponding microstructural evolution of cemented soils. Initially, unconfined compressive strength tests (UCS) were conducted on Nano-MgO-modified cemented soils subjected to different curing periods in freshwater and seawater environments. The findings revealed that the addition of 3% Nano-MgO effectively increased the compressive strength and corrosion resistance of the cemented soils. Subsequent dynamic cyclic loading tests demonstrated that Nano-modified cemented soils exhibited reduced energy loss (smaller hysteresis loop curve area) under cyclic loading, along with a significant improvement in the damping ratio and dynamic elastic modulus. Furthermore, employing an array of microscopic analyses, including nuclear magnetic resonance (NMR), X-ray diffraction (XRD), and scanning electron microscopy (SEM), revealed that the hydration byproducts of Nano-MgO, specifically Mg(OH)2 and magnesium silicate hydrates, demonstrated effective pore space occupation and enhanced interparticle bonding. This augmentation markedly heightened the corrosion resistance and durability of the cemented soil.

Microbially induced carbonate precipitation (MICP) is an eco-friendly technique for weak soil reinforcement. In this study, Sporosacina pasteurii was used to strengthen silty sand after multigradient domestication in an artificial seawater environment. The efficiency of MICP was investigated by carrying out a series of macroscopic and microscopic tests on biocemented silty sand specimens. It was found that the salt ions in seawater impacted bacterial activity. The best activity of the bacterial solution in the seawater environment was achieved after five-gradient domestication, which was approximately 8% lower than that in the deionized water environment. The significant effects of domesticated bacteria on silty sand reinforcement were demonstrated by the content of precipitated carbonate and the unconfined compressive strength (UCS) of the treated specimens. The seawater positively impacted the MICP procedure due to the roles of calcium and magnesium ions, indicated by the X-ray diffraction spectra. The scanning electron microscopy (SEM) results showed that carbonate precipitations distributed primarily on the surfaces and near the contact points of the soil particles, contributing to the soil strength. The cementation solution concentration and injection rate significantly influenced the content and distribution of carbonate precipitations and UCS of the biocemented silty sand, and the values corresponding to good reinforcement efficiency were 1.0 mol/L and 1.0 mL/min, respectively. The results of consolidated undrained triaxial tests showed that the mechanical properties of treated specimens were influenced by biocementation cycles. It was found that the stress-strain behavior of biocemented samples changed from strain hardening to strain softening when the number of reinforcement cycles increased. The peak strength of silty sand was increased by 1.9-3 times after 5 times MICP treatment. The effect of biocementation cycles on the shear strength parameters could be represented by relating the effective friction angle and effective cohesion of biocemented silty sand to the carbonate content.

The studied region is located in the southwestern Iran and on the border of Iran and Iraq. In the past, this region had dense palm groves and abundant plants. However, due to the decrease in upstream discharge, in recent years, saline and sodium seawater has intrusion in the river and affected the agricultural lands along its sides. This event has caused irreparable and serious damage to the agricultural industry in the region, turning this area into a graveyard of date palm trees. Understanding the characteristics of agricultural soils for their improvement and/or planting appropriate plants is one of the goals of sustainable agriculture. Considering the damage of the studied area from the intrusion of salt water in the Arvand River, this study investigated important characteristics of soil salinity including EC, pH, C.E.C, SAR and ESP. In this research, sampling of agricultural soils along the riverside was carried out in three different horizons and two line parallel to the river and at two different distances. Statistical methods of correlation coefficient, hierarchical analysis and factor analysis were used to identify the factors affecting soil quality and the relationships between parameters. The results showed that due to the intrusion of sodium seawater, the soils of the studied area have become saline-sodium, and the salinity level in the soils near the river mouth is higher than that in the soils on the upstream side of the river. In terms of fertility, the cation exchange capacity is in the medium range, and the clay texture and abundant organic matter of the soil as a result of the remaining plant and tree residues have an important effect on this parameter.

Understanding the effects of seawater on solidified soil is crucial for its application in ocean engineering, especially when using marine dredged clay as raw material. In this study, Comparative experiments, comprising unconfined compressive strength (UCS) tests and scanning electron microscopy (SEM) analyses, were conducted under both seawater and standard curing conditions to investigate the combined effects of additives, curing environments, and seawater on soil properties. Results show that seawater significantly weakens the mechanical performance of solidified soil. Compared to standard curing, solidified soil with ordinary Portland cement (OPC) showed an average strength reduction of 38.65 % after 7 days and over 29.28 % after 28 days. In contrast, solidified soil prepared with sulphoaluminate cement (SAC) exhibited greater resistance to seawater, with strength reductions of 28.69 % after 7 days and 20.19 % after 28 days. Polyacrylamide (PAM) can enhance the early strength of solidified soil in seawater by forming a composite structure with hydration products. An increase of 0.5 % in PAM content leads to an average strength improvement of 27.03 % at 7 days and 34.61 % at 14 days. In contrast, for every 1 % increase in superplasticizer (SP) content, the soil strength in seawater decreases by 17.78 %, 11.20 %, and 9.24 % at 7, 14, and 28 days, respectively. These findings provide important insights for improving solidified soil performance in marine environments.

The prevalent presence of microplastics in marine environments poses major ecological risks requiring innovative approaches to their management and reduction. This study addresses a knowledge gap in biodegradable microplastic alternatives by looking at the biodegradability and properties of reclaimed microplastic polypropylene (PP) blended with polylactic acid (PLA). The study lies in the systematic exploration of various PP/PLA formulations, evaluating their potential for enhanced biodegradability without significantly compromising mechanical performance. Microplastic PP and PLA blends were prepared in various ratios using the melt blending method. The blend was characterized using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) to confirm the presence and morphology of the components. The mechanical properties were evaluated using tensile strength tests. A blend of 90% PP and 10% PLA was found to retain the highest tensile strength even after immersion in seawater. The thermal stability and degradation behavior were analyzed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). This shows that increasing PLA content affects the thermal properties of the blends. Seawater immersion and soil burial tests were used to assess the biodegradability of the blends. The results showed that the blends' biodegradation was confirmed by increases in conductivity and salinity in the seawater and weight loss in the soil burial. The major findings show that blending PP and PLA improves biodegradability while maintaining adequate mechanical properties. Tests including immersion in saltwater and soil burial were used to assess the biodegradability of the blends. The results showed that the blends' biodegradation was confirmed by increases in conductivity and salinity in the seawater and weight loss in the soil burial. The major findings show that blending PP and PLA improves biodegradability while maintaining adequate mechanical properties. Finally, this study presents a new approach to reducing microplastic pollution through the blend of reclaimed PP with biodegradable PLA, resulting in a sustainable material with improved environmental performance. Future studies should look into new formulations, biodegradable polymers, and long-term degradation tests under a variety of environmental circumstances.