A comprehensive series of tests, including dynamic triaxial, monotonic triaxial and unconfined compressive strength (UCS) tests, were carried out on reconstituted landfill waste material buried for over twenty years in a closed landfill site in Sydney, Australia. Waste materials collected from the landfill site were treated with varying percentages of cement, and both treated and untreated specimens were investigated to evaluate the influence of cement treatment. The study examined the dynamic properties of cement-treated landfill waste, including cumulative plastic deformation, resilient modulus, and damping ratio, and also analysed the impact of cyclic loading on post-cyclic shear strength in comparison to pre-cyclic shear strength. The UCS tests and monotonic triaxial tests demonstrated that untreated specimens subjected to monotonic loading exhibited a progressive increase in strength with rising axial strain, whereas cement-treated specimens reached a peak strength before experiencing a decline. During cyclic loading, with the inclusion of cement, a significant reduction in cumulative plastic deformation and damping ratio was observed, and this reduction was further enhanced with increasing cement content. Conversely, the resilient modulus showed substantial improvement with the addition of cement, and this enhancement was further amplified with increasing cement content. The formation of cementation bonds between particles curtails particle movement within the landfill waste material matrix and prevents interparticle sliding during cyclic loading, leading to lower plastic strains and damping ratio while increasing resilient modulus. Post-cyclic monotonic testing revealed that cyclic loading caused the partial breakage of the cementation bonds, resulting in reduced shear strength. This reduction was higher on samples treated with lower cement content. Overall, the findings of the research offer crucial insights into the possibility of cement-treated landfill waste as a railway subgrade, laying the groundwork for informed design decisions in developing transport infrastructure over closed landfill sites while using landfill waste materials available on site.

The large coal production and consumption has caused environmental problems worldwide as a source of energy production with irreparable effects on soil, water, and the ecosystem. In addition, producing coal waste in coal washing plants and burying it intensifies the issue in nature. Due to the rising generation of coal waste from various sources, this study utilized several forms of coal waste obtained from a coal-washing plant in the production of both structural concrete (with a water-cement ratio of 0.54) and non-structural concrete (with a water-cement ratio of 0.7). The impact of coal waste on compressive strength (CS) was examined at curing ages of 7, 28, and 56 days. Various percentages of coal waste were substituted for both cement and sand. A superplasticizer was incorporated into the concrete mixtures to enhance the workability and achieve the desired slump and strength levels. According to the compressive strength findings, the ideal replacement level of sand with jig coal waste was 30 %. For 56-day-old specimens, the optimal substitution rates for cement with jig coal waste powder, flotation coal waste, and coal waste ash were found to be 10 %, 10 %, and 20 %, respectively. Notably, adding 10 % coal waste powder and coal waste ash increased compressive strength by 22 %, 23 %, and 44 % at 56 days.

Contact Lens (CLs) are often disposed of via toilet or sinks, ending up in the wastewater treatment plants(WWTPs). Millions of CLs enter WWTPs worldwide each year in macro and micro sizes. Despite WWTPs'ability to remove solids, CLs can persist and potentially contaminate watercourses and soils. This study evaluates whether different CLs degrade in WWTP aeration tanks. Six daily CLs (Nelfilcon A,Delefilcon A, Nesofilcon A, Stenfilcon A, Narafilcon A, Somofilcon A) and four monthly CLs (Lotrafilcon B,Comfilcon A, Senofilcon A, and Samfilcon A) were immersed in aeration tanks for twelve weeks. Theirphysical and chemical properties, including water content (WC), refractive index (RI), chemical prop-erties (Fourier Transform Infrared Spectroscopy), and mechanical properties were assessed. Results show that all CLs maintained their physical appearance after 12 weeks. Neither Nelfilcon A norNarafilcon A exhibited significant changes in WC and RI, (p>0.05, Tukey test), while other daily lensesshowed variations in at least one parameter. Among monthly CLs, only Senofilcon A showed significant differences in both WC (p0.05 Tukey test). However, Somofilcon A displayed significant changes in stress at break (p<0.0001,Tukey test), and Elongation at Break (p<0.05, Tukey test). No changes were found in the chemicalstructure of any CLs suggesting that twelve weeks in WWTP aeration tanks is insufficient for CLsdegradation. Thesefindings highlight CLs as a potential emerging pollutant, emphasizing their persis-tence in sludge or migration into watercourses and soils (c) 2025 The Authors. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. Thisis an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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 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.

In this study, carbide slag, fly ash, cement, and sodium sulfate were used to stabilize silt from the Yellow River Alluvial Plain. An orthogonal test was conducted to evaluate the optimal mix design for soil stabilization. The mechanical properties, hydration products, and microstructure of the stabilized silt were examined. The effects of stabilizer concentration, compaction, and moisture content on the mechanical properties were investigated. Based on mechanical performance, the optimal stabilizer mix was found to consist of 30% cement, 13.6% carbide slag, 54.4% fly ash, and 2% sodium sulfate. The results indicated that the California Bearing Ratio (CBR), unconfined compressive strength, and splitting tensile strength of the stabilized silt increased with higher stabilizer dosage and compaction degree. In the early stages, the hydration products of the stabilized silt were primarily calcium hydroxide, ettringite, and C-S-H, which exhibited a loose structure. Over time, the microstructure densified, and more crystalline C-S-H was formed. This study provides valuable insights into the use of industrial by-products for soil stabilization, offering a sustainable and cost-effective solution to improve the strength and stability of silt in construction projects.

Thermochemical processing of biowaste generates renewable carbon-rich materials with potential agronomic uses, contributing to waste valorization. This study evaluates the application of hydrochar obtained from hydrothermal carbonization of food waste, those obtained by different post-treatments (washing, aging, and thermal treatment), as well as biochar obtained by pyrolysis as soil amendments. For this purpose, the effect of char addition (1-10 wt% d.b.) on a marginal agricultural soil on germination and growth of Solanum lycopersicum (tomato) plants was assessed. All the hydrochars exhibited a chemical composition suitable for agronomic use, characterized by high nutrient content, abundant organic matter, and low concentration of phytotoxic metals. In contrast, biochar exceeded the permissible limits for Cr, Cu, and Ni concentrations rendering it unsuitable for application to agronomic crops. The high temperature of thermal post-treatment and pyrolysis favored mineral and heavy metal concentration while washing significantly reduced nutrient content (N, S, P, K, Mg) along with the electrical conductivity. The addition of biochar or both washed and thermally post-treated hydrochar negatively affected tomato growth. Reduced chlorophyll content was associated with the decreased expression of genes encoding enzymes involved in antioxidant metabolism. This led to photosynthetic membrane damage, as evidenced by chlorophyll fluorescence-related parameters. Conversely, the addition of aged (<= 5 wt %) and fresh (1-10 wt%) hydrochars increased both germination and plant growth compared to unamended soil, indicating that hydrochar from food waste does not require additional post-treatments to be used as a soil amendment.

The solidification of dredged marine sediments with high water content is important for maintenance dredging and reclamations. To reduce the carbon emission of solidification, low-carbon recycled wastes such as incinerated sewage sludge ash (ISSA) and ground granulated blastfurnace slag (GGBS) have been recently adopted as binding materials to replace conventional Portland cement. For soil slurry with ultra-high water content, using the consolidationsolidification combined method is an effective way to reduce the volume and improve the final mechanical properties. However, it is unclear how the consolidation interacts with solidification using the binding materials. In this study, a series of laboratory tests were conducted on dredged Hong Kong marine deposit slurry mixed with ISSA and GGBS with alkali activation by lime. The elemental consolidation tests controlled with different constant rates of strain and multistage loadings demonstrate that the rate of consolidation has significant effects on volume reduction and yielding stress development during consolidation-solidification treatment. Consolidationsolidification achieves higher volume reduction and yielding stress than pure solidification. As the rate of consolidation decreases, there is a smaller volume reduction at the same effective stress and less yielding stress enhancement at the same curing time. A scanning electron microscope with energy dispersive spectrometer was used to investigate hydration products and soil fabric after treatment. The slower rate of consolidation causes the looser structure and finer needleshaped products with the same curing period, which can explain the mechanical properties observed from the element tests.

The use of nano-materials as a stabilizing agent in soils has a significant role, particularly in improving their mechanical properties. This study investigates the impact of stabilization using nano-materials, specifically nano-cement, on natural and contaminated clays. A series of laboratory tests, including Atterberg limits, compaction, unconfined compressive strength, permeability, and consolidation, are conducted to evaluate the soil properties. Various percentages of nano-cement (0 %, 0.5 %, 1 %, 1.5 %, and 2 %) are added to two sample groups; one prepared with water and the other with leachate. Based on the results of Atterberg limits tests, adding 2 % nano-cement to natural clay increases the liquid limit by 8.6 % and decreases the plasticity index by 16 %. These values diminish to 8.3 % and 13 % for contaminated clay. Furthermore, according to the compaction test results, increasing nano-cement content by up to 2 % leads to a reduction in maximum dry density by about 11.5 % and an increase in optimum moisture content by about 15.9 %. However, these values change to 5.77 % and 32.25 % for contaminated clay. The results indicate that increasing nano-cement content generally improves the strength and stiffness of the soil while reducing its permeability. On the other hand, contamination of the soil leads to a reduction in strength and stiffness, while permeability increases. Based on the Field Emission Scanning Electron Microscopy (FESEM) analysis, the incorporation of nano-cement improved the microstructure by decreasing pore spaces and enhancing bonding between particles. While chemical complexity of leachate negatively affects nano-cement dispersion, which leads to increased particle aggregation.

When processing barley for the brewing and food industries, one of the process steps is the separation of barley grains. After separation, waste fractions are created that contain damaged grains, dust, stones, grass, clay residues, etc. The waste fractions therefore contain recyclable components. It is important to find a suitable way to use these waste fractions. This research is focused on the possibilities of applying torrefied waste fractions as soil enrichment to support plant growth. The first waste fraction contained lower-quality barley grains that are used as feed for livestock. The second waste fraction contained grass seeds and chaff and can be used as feed for forest animals. The third waste fraction, which contained aspiration dust, is currently being incinerated and disposed at biogas plants. Experiments were conducted with different ratios of torrefied fractions added to the soil and the values of total nitrogen were analyzed as an indicator of the benefit to the soil. The results showed that torrefied waste fractions exhibit positive properties for plant growth. The best results were achieved with a mixture containing 10 and 50 % of soil enriched with torrefied second and third waste fractions. Experiments confirmed a positive effect on plant growth, which suggests the possibility of applying this procedure in practice. Compared to current research, this method can contribute to the sustainable management of biowaste and its effective use for improving soil conditions with a high potential for sustainable agriculture.