Enhancing the structural stability of Pisha sandstone soil is an important measure to manage local soil erosion. However, Pisha sandstone soil is a challenging research hotspot because of its poor permeability, strong soil filtration effect, and inability to be effectively permeated by treatment solutions. In this study, by adjusting the soil water content to improve the spatial structure of the soil body and by conducting unconfined compressive strength and calcium ion conversion rate tests, we investigated the effect of spatial distribution differences in microbial-induced calcium carbonate deposition on the mechanical properties of Pisha sandstone-improved soil in terms of the amounts of clay dissolved and calcium carbonate produced. The results demonstrate that improving the soil particle structure promotes the uniform distribution of calcium carbonate crystals in the sand. After microbial-induced carbonate precipitation (MICP) treatment, the bacteria adsorbed onto the surface of the Pisha sandstone particles and formed dense calcium carbonate crystals at the contact points of the particles, which effectively enhanced the structural stability of the sand particles, thereby improving the mechanical properties of the microbial-cured soils. The failure mode of the specimen evolved from bottom shear failure to overall tensile failure. In addition, the release of structural water molecules in the clay minerals promoted the surface diffusion of calcium ions and accelerated the nucleation and crystal growth of the mineralization products. In general, the rational use of soil structural properties and the synergistic mineralization of MICP and clay minerals provide a new method for erosion control in Pisha sandstone areas.

Salinization of road base aggregates poses a critical challenge to the performance of coastal roads, as the intrusion of chlorine salts adversely affects the stability and durability of pavement structures. To investigate the cyclic behavior of salinized road base aggregates under controlled solution concentration, c, and crystallization degree, omega, a series of unsaturated cyclic tests were conducted with a large-scale triaxial apparatus. The results showed that variations in solution concentration had a negligible influence on the resilient modulus of road base aggregates, and no significant differences were observed in their shakedown behavior. However, the long-term deformational response of the aggregates was affected by the precipitation of crystalline salt. At low crystallization degrees, a significant increase in accumulated axial strain and a decrease in resilient modulus were observed with increasing omega. Once the crystallization degree exceeded a critical threshold (omega(c)), there was a reduction in accumulated strain and an increase in resilient modulus. The precipitation of crystalline salt also disrupted the shakedown behavior of road base aggregates. During the nascent stages of crystallization (omega < 0.33), the presence of fine crystalline powders and clusters in the saltwater mixture destabilized the soil skeleton, resulting in a transition from the plastic shakedown stage to the plastic creep stage. This poses potential risks to the long-term characteristics and durability of the road base courses.

To overcome the limitations of microscale experimental techniques and molecular dynamics (MD) simulations, a coarse-grained molecular dynamics (CGMD) method was used to simulate the wetting processes of clay aggregates. Based on the evolution of swelling stress, final dry density, water distribution, and clay arrangements under different target water contents and dry densities, a relationship between the swelling behaviors and microstructures was established. The simulated results showed that when the clay-water well depth was 300 kcal/mol, the basal spacing from CGMD was consistent with the X-ray diffraction (XRD) data. The effect of initial dry density on swelling stress was more pronounced than that of water content. The anisotropic swelling characteristics of the aggregates are related to the proportion of horizontally oriented clay mineral layers. The swelling stress was found to depend on the distribution of tactoids at the microscopic level. At lower initial dry density, the distribution of tactoids was mainly controlled by water distribution. With increase in the bound water content, the basal spacing expanded, and the swelling stresses increased. Free water dominated at higher water contents, and the particles were easily rotated, leading to a decrease in the number of large tactoids. At higher dry densities, the distances between the clay mineral layers decreased, and the movement was limited. When bound water enters the interlayers, there is a significant increase in interparticle repulsive forces, resulting in a greater number of small-sized tactoids. Eventually, a well-defined logarithmic relationship was observed between the swelling stress and the total number of tactoids. These findings contribute to a better understanding of coupled macro-micro swelling behaviors of montmorillonite-based materials, filling a study gap in clay-water interactions on a micro scale. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Recycled aggregates (RA) from construction and demolition waste have many shortcomings such as high porosity and low strength due to adhered mortar and defects inside. If the defects (micropores and microcracks) of RA were repaired, the quality of RA could be improved greatly and its application could be further enlarged. Our previous study has proposed a new modification method, enzyme-induced carbonate precipitation (EICP), to repair the internal defects of RA. In this study, the efforts were focused on the optimization of the EICP treatment. It was found that the two-step immersion method, consisting of preimmersing in CO(NH2)2-Ca(NO3)2 solution for 24 h, then adding urease solution at once with single treatment duration of 5 days and cycling two treatments, was the optimal treatment. Compared with the untreated RA, the water absorption and crush value of treated recycled concrete aggregates (T-CA) were decreased by 7.01% and 9.91%, respectively, and 21.59% and 14.40% for treated recycled mixed aggregates (T-MA), respectively. By use of the optimized EICP-treated RA, the compressive strength of concrete increased by 6.05% (T-CA concrete) and 9.23% (T-MA concrete), and the water absorption of concrete decrease by 11.46% (T-CA concrete) and 18.62% (T-MA concrete). This indicates that the optimized EICP treatment could reduce the porosity and improve the strength of aggregates, thus enhancing the mechanical properties and impermeability of recycled concrete.

This experimental study is to find a solution to reduce the amount of waste and at the same time improve the geotechnical properties of fine soils. Compaction, odometer, direct shear tests, and unconfined compression tests were carried out on a clay with a very high degree of plasticity mixed with 0%, 10%, 20%, 30%, and 40% of recycled concrete aggregates (RCA). The addition of concrete aggregates to the clayey soil shows an increase in the maximum dry density and a reduction in the optimum water content. The odometer tests results showed that the increase in the recycled material content leads to a decrease in the compression index, swelling index and creep index. On the other hand, the pre-consolidation stress, the odometric modulus, the consolidation coefficient and the permeability coefficient increase with increasing RCA content. According to the direct shear test, the higher RCA content provided an improvement in shear strength which is accompanied by an increase in the dilatant character. For different curing times and for a content of 10% recycled concrete aggregate, the unconfined compressive strength increased compared to the untreated soil.

Background and aims The changes in soil physical properties caused by root exudates depend largely on the chemical composition of root exudates. Our aim was to explore the effects of non-specific root exudates on the physical properties of soil change. Methods Five sugar compounds, five amino acid compounds, and five organic acid compounds were selected and added to loess as three single addition treatments (amino acids, organic acids, and sugars) and four combined addition treatments (amino acids + organic acids, amino acids + sugars, organic acids + sugars, and amino acids + organic acids + sugars). Soil water repellency, aggregate stability, and shear resistance tests were performed on the loess. Results The treatments sugars, amino acids, and amino acids + sugars significantly increased soil water repellency. In addition, organic acids + sugars maximised mean weight diameter (MWD), geometric mean diameter (GMD) and the content of > 0.25 mm water-stable aggregates (R0.25), and minimised the percentage of aggregates destroyed (PAD) in the addition treatments. All treatments except for amino acids significantly increased soil shear strength and cohesion of the loess. Amino acids, amino acids + sugars, and amino acids + organic acids + sugars significantly increased the internal friction angle. Conclusion The single addition treatments had a higher effect on soil hydraulic properties, while the combined addition treatments had a higher effect on soil mechanical properties. Sugars and amino acids substantially increased soil hydraulic stability. Sugars combined with other compounds, especially with organic acids, significantly improved soil mechanical stability.

The accumulation of soil organic carbon (SOC) and total nitrogen (TN) is easily accomplished by returning crop straw, which strongly affects the formation and pore structure of aggregates, especially in black soil. We returned maize straw at different rates (6,000, 9,000, 12,000 and 15,000 kg ha(-1)) for nine years to investigate its influence on the SOC and TN contents in the SOC fractions of aggregates by combining size and density fractionation. Their subsequent influences on pore morphology and size distribution characteristics were examined using X-ray micro-computed tomography scanning (mu CT). The results showed that returning straw significantly increased the contents of C and N in the SOC fractions of aggregates, especially at the return rates of 12,000 and 15,000 kg ha(-1), which in turn promoted aggregate formation and stability, and ultimately amended pore structure. The pore size>100 mu m, porosity (>2 mu m), and morphological characteristics (anisotropy, circularity, connectivity and fractal dimension) significantly increased, but the total number of pores significantly decreased (P<0.05). Our results indicated that the amendment of the pore morphology and size distribution of soil aggregates was primarily controlled by the higher contents of C and N in the density fractions of aggregates, rather than in the aggregate sizes. Furthermore, this pore network reconfiguration favored the storage of C and N simultaneously. The findings of this study offer valuable new insights into the relationships between C and N storage and the pore characteristics in soil aggregates under straw return.

The relationships between soil aggregates, aggregate-associated carbon (C), and soil compaction indices in pomegranate orchards of varying ages (0-30 years) in Assiut, Egypt, were investigated. Soil bulk density (Bd) and organic carbon (OC) content increased with orchard age in both the surface (0.00-0.20 m) and subsurface (0.20-0.40 m) layers 0.20-0.40 m). The percentage of macroaggregates (R-0.25) and their OC content in the aggregate fraction > 0.250 mm increased as the pomegranate orchard ages increased in the surface layer (0.00-0.20 m). Older pomegranate orchards show improved soil structure, indicated by higher mean weight diameter (MWD) and geometric mean diameter (GMD), alongside reduced fractal dimension (D) and erodibility (K). As orchard ages increased, maximum bulk density (BMax) decreased due to an increase in OC, while the degree of compactness (DC) increased, reaching a maximum at both soil layers for the 30 Y orchards. Soil organic carbon and aggregate-associated C significantly influenced BMax, which led to reducing the soil compaction risk. Multivariate analyses identified the >2 mm aggregate fraction as the most critical factor influencing the DC, soil compaction, and K indices in pomegranate orchards. The OC content in the >2 mm aggregates negatively correlated with BMax, DC, and K but was positively associated with MWD and GMD. Moreover, DC and Bd decreased with higher proportions of >2 mm aggregates, whereas DC increased with a higher fraction of 2-0.250 mm aggregation. These findings highlight the role of aggregate size fractions and their associated C in enhancing soil structure stability, mitigating compaction, and reducing erosion risks in pomegranate orchards.

Mercury is a significant environmental pollutant and public health threat, primarily recognized for its neurotoxic effects. Increasing evidence also highlights its harmful impact on the cardiovascular system, particularly in adults. Exposure to mercury through contaminated soil, air, or water initiates a cascade of pathological events that lead to organ damage, including platelet activation, oxidative stress, enhanced inflammation, and direct injury to critical cells such as cardiomyocytes and endothelial cells. Endothelial activation triggers the upregulation of adhesion molecules, promoting the recruitment of leukocytes and platelets to vascular sites. These interactions activate both platelets and immune cells, creating a pro-inflammatory, prothrombotic environment. A key outcome is the formation of platelet-leukocyte aggregates (PLAs), which exacerbate thromboinflammation and endothelial dysfunction. These processes significantly elevate cardiovascular risks, including thrombosis and vascular inflammation. This study offers a comprehensive analysis of the mechanisms underlying mercury-induced cardiotoxicity, focusing on oxidative stress, inflammation, and cellular dysfunction. [GRAPHICS] .

High plasticity clay soils have low bearing and high swelling potential, which can lead to major problems if used in embankment layers. In current study, recycled concrete aggregates (RCA) were used as the most important part of construction and demolition (C&D) wastes in order to reduce the swelling potential and improve the mechanical strenght of high plasticity clay soil, and to achieve these goals, granulated blast furnace slag (GBS) was used as chemical additive. A set of laboratory tests including standard proctor, unconfined compression strength (UCS) and CBR tests were conducted to investigate the mechanical properties of the treated soil. Laboratory observations showed that by adding of RCA wastes to high plasticity clay, the UCS value increased up to 20% RCA content and then decreased with further RCA. Also, adding GBS and prolonged curing time improves the UCS of the clay - RCA mixture, and addition of 9% GBS can be suggested as the optimal content to achieve the design criteria of the subbase and subgrade layers. The use of RCA improves the secant modulus of elasticity (E50) and reduces the deformability index (DI), and these parameters are improved more significantly in the presence of GBS additive.