Search Results (67)

Forests are a key terrestrial carbon sink, storing carbon in biomass, the forest floor, and the mineral soil (SOC). Since Pinus radiata D. Don is the most widely planted forest species in Chile, it is important to understand how environmental and soil factors influence these carbon pools. Our objective was to evaluate the effects of climate and site variables on carbon stocks in adult radiata pine plantations across contrasting water and nutrient conditions. Three 1000 m² plots were installed at 20 sites with sandy, granitic, recent ash, and metamorphic soils, which were selected along a productivity gradient. Biomass carbon stocks were estimated using allometric equations, and carbon stocks in the forest floor and mineral soil (up to 1 m deep) were assessed. SOC varied significantly, from 139.9 Mg ha⁻¹ in sandy soils to 382.4 Mg ha⁻¹ in metamorphic soils. Total carbon stocks (TCS) per site ranged from 331.0 Mg ha⁻¹ in sandy soils to 552.9 Mg ha⁻¹ in metamorphic soils. Across all soil types, the forest floor held the lowest carbon stock. Correlation analyses and linear models revealed that variables related to soil water availability, nitrogen content, precipitation, and stand productivity positively increased SOC and TCS stocks. In contrast, temperature, evapotranspiration, and sand content had a negative effect. The developed models will allow more accurate estimation estimates of C stocks at SOC and in the total stand. Full article

The long-term wear resistance of granite manufactured sand (HGY) concrete has not been sufficiently investigated. This deficiency makes it difficult to accurately predict and evaluate the service life and durability of such concrete pavements in practical engineering applications. Consequently, this study employed a self-developed indoor abrasion test device and combined it with scanning electron microscope (SEM) and X-ray diffraction (XRD) technologies. From the two dimensions of macroscopic performance and microscopic structure, the mechanisms’ influence of the effective sand ratio, stone powder content, and fine aggregate lithology on the wear resistance of HGY concrete were systematically investigated. The optimal content of the effective sand and stone powder content were determined, and the long-term evolution law of the wear resistance of HGY concrete was revealed. The results demonstrate that increasing the effective sand content will reduce the mass loss of concrete. When the stone powder content is 9%, the wear resistance of the concrete is optimal. The order of mass loss of different fine aggregate lithologies is river sand (HS) > limestone mechanism sand (SHY) > HGY, and the wear resistance of HGY is better than that of other fine aggregates. Increasing the effective sand content can enhance the bonding strength between the aggregate and the cement matrix and reduce the porosity, which is conducive to improving the wear resistance of the concrete. Under a relatively small stone powder content, as the amount of stone powder added increases, the pore structure becomes tighter, and the wear resistance of the concrete becomes better. Compared to HS, the manufactured sand (MS) containing stone powder can optimize the pore structure and hydration products of concrete, improve the pore structure of concrete, and improve the wear resistance. Full article

The elastic modulus is one of the fundamental parameters controlling the mechanical behaviour of concrete. In this study, the Movable Cellular Automata (MCA) method is applied to predict the Young’s modulus of concrete based on the properties of its components. Each automaton represents one component: cement paste, fine aggregate, or coarse aggregate. A parametric sensitivity analysis was performed using Grey System Theory (GST) on hypothetical concrete modeled with the MCA method. The analysis showed that the coarse aggregate type, coarse aggregate-to-total aggregate ratio, and water-to-cement ratio have the greatest impact on the Young’s modulus. To test the effectiveness of the MCA method in modelling concrete, results of numerical simulations were compared with experimental data available in the literature. The first numerical simulations were conducted for mortars containing cement paste and sand as well as for concretes produced by adding granite to them. Two approaches were used to perform the simulations; in the first approach, a sample contained automata representing cement paste, sand, and granite, while in the second the automata represented mortar and granite. High consistency was achieved, with results from both approaches differing by only 0.6%. Subsequent simulations focused on concretes with different water-to-cement ratios (0.45, 0.55, and 0.65), the origin of the basaltic aggregate, and various aggregate contents (60%, 54%, 48%, and 42%). Results showed high agreement between simulations and experimental data, confirmed by a high coefficient of determination R² of 0.84 and mean squared error of 2.43 GPa². Finally, simulations were performed for lightweight expanded clay aggregate concrete, resulting in an R² of 0.86 and mean squared error of 0.81 GPa², which demonstrates the effectiveness of the MCA method in predicting the static elastic modulus of concrete. Full article

The Lhasa River, as one of the major rivers on the Tibetan Plateau, is of great value for the study of climate and environmental changes on the Tibetan Plateau. In this paper, the grain size and the mineralogical and geochemical characteristics of the sediments from the Lhasa River were investigated. The results show the following: (1) The average grain size of the Lhasa River sediments is coarse (65.5% sand, 23.6% silt), and the sorting is overall poor; the skewness is mostly positive, and the kurtosis is wide, which reflects the obvious characteristics of river sand deposition. (2) The mineral composition of the Lhasa River sediments is dominated by quartz (38.4%), feldspar, and plagioclase feldspar, followed by clay minerals, and the content of carbonate minerals is relatively low; the content of clay minerals in the illite content is as high as 83.3%, while the chlorite content is slightly higher than kaolinite, and smectite content is very low. The chemical index of illite is less than 0.4, indicating that illite is mainly iron-rich magnesium illite. (3) The value of the chemical weathering index (CIA) of the sediments is low, implying that the sediments are in a weak–moderate chemical weathering state and dominated by physical weathering. Comprehensive analyses further revealed that the weathering process of the sediments in the Lhasa River was influenced by both climate and lithology, i.e., sediment composition is influenced not only by chemical weathering in a dry, cold climate but also by physical weathering of granites exposed over large areas. The results of this study can provide scientific references for further in-depth research on the environmental and climatic effects of the Tibetan Plateau. Full article

This research presents a proposal for alkali-activated permeable concrete composites with the use of industrial by-products, including ground granulated blast-furnace slag (GGBS) and waste-foundry sand, as well as agro-desecrate product, i.e., sugarcane bagasse ash (SBA). GGBS and SBA served as binders, with crushed granite as coarse aggregate and waste-foundry sand as fine aggregate. The novelty of this proposal is in examining the influence of SBA, in combination with slag, on the fresh- and hardened-state properties of the proposed permeable concretes. Experiments were conducted to optimize the SBA percentage based on hydraulic conductivity and compressive and tensile strength after 28 days of air curing. The hardened density, compaction factor (workability), and saturated water absorption were also measured for all the mixes. Furthermore, the control and optimal mixes were subjected to evaluate the microstructure analysis (EDX, XRD, and FESEM) after 28 days of air curing. The mix containing 100% GGBS and 0% SBA served as the reference, with the optimal 10% SBA mix (with 90% GGBS) used for comparative analysis to understand its effect on the properties of permeable composites. The results showed positive or acceptable mechanical performance at a mix ratio of 10% SBA to 90% GGBS as binders. This study aims to enhance the understanding of the engineering behavior of alkali-activated permeable composites, facilitating the rational design of permeable pavement systems through the effective use of agro-industrial waste products, thereby conserving ecosystems while meeting engineering requirements. Full article

To study the bearing characteristics of rock-socketed single piles on the southeast coast of Fujian Province, we conducted similar material ratio tests and single pile model tests. Initially, based on the mechanical parameters of strongly weathered granite, 10 groups of similar material samples were prepared using iron concentrate powder, barite powder, and quartz sand as aggregates, with rosin and alcohol as the cementing agents and gypsum as the modulating agent. Through triaxial testing and range and variance analysis, it was determined that the binder concentration has the most significant impact on the material properties. Consequently, Specimen 1 was selected as the simulation material. In the model test, the strongly weathered granite stratum was simulated using the ratio of Specimen 1. A horizontal load was applied using a pulley weight system, and the displacement at the top of the pile was measured with a laser displacement meter, resulting in a horizontal load–displacement curve. The results indicated that the pile foundation remained in an elastic state until a displacement of 2.5 mm. Measurements of the horizontal displacement and bending moment of the pile revealed that the model pile behaves as a flexible pile; the bending moment initially increases along the pile length and then decreases, approaching zero at the pile’s bottom. The vertical load test analyzed the relationship between vertical load and settlement of the single pile, as well as its variation patterns. This study provides an experimental basis for the design of single pile foundations in weathered granite formations on the southeast coast of Fujian Province and aids in optimizing offshore wind power engineering practices. Full article

Quaternary stream sediments and beach black sand in north-western Saudi Arabia (namely Wadi Thalbah, Wadi Haramil and Wadi Al Miyah) are characterized by the enrichment of heavy minerals. Concentrates of the heavy minerals in two size fractions (63–125 μm and 125–250 μm) are considered as potential sources of “strategic” accessory minerals. A combination of mineralogical, geochemical and spectroscopic data of opaque and non-opaque minerals is utilized as clues for provenance. ThO₂ (up to 17.46 wt%) is correlated with UO₂ (up to 7.18 wt%), indicating a possible uranothorite solid solution in zircon. Hafnoan zircon (3.6–5.75 wt% HfO₂) is a provenance indicator that indicates a granitic source, mostly highly fractionated granite. In addition, monazite characterizes the same felsic provenance with rare-earth element oxides (La, Ce, Nd and Sm amounting) up to 67.88 wt%. These contents of radionuclides and rare-earth elements assigned the investigated zircon and monazite as “strategic” minerals. In the bulk black sand, V₂O₅ (up to 0.36 wt%) and ZrO₂ (0.57 wt%) are correlated with percentages of magnetite and zircon. Skeletal or star-shaped Ti-magnetite is derived from the basaltic flows. Mn-bearing ilmenite, with up to 5.5 wt% MnO, is derived from the metasediments. The Fourier-transform infrared transmittance (FTIR) spectra indicate lattice vibrational modes of non-opaque silicate heavy minerals, e.g., amphiboles. In addition, the FTIR spectra show O-H vibrational stretching that is related to magnetite and Fe-oxyhydroxides, particularly in the magnetic fraction. Raman data indicate a Verwey transition in the spectrum of magnetite, which is partially replaced by possible ferrite/wüstite during the measurements. The Raman shifts at 223 cm⁻¹ and 460 cm⁻¹ indicate O-Ti-O symmetric stretching vibration and asymmetric stretching vibration of Fe-O bonding in the FeO₆ octahedra, respectively. The ultraviolet-visible-near infrared (UV-Vis-NIR) spectra confirm the dominance of ferric iron (Fe³⁺) as well as some Si⁴⁺ transitions of magnetite (226 and 280 nm) in the opaque-rich fractions. Non-opaque heavy silicates such as hornblende and ferrohornblende are responsible for the 192 nm intensity band. Full article

Seedling establishment is often a critical bottleneck in the revegetation of mine tailings and similar substrates. Biochar and deactivated yeast are potential sustainable materials that could be used in this context as seed coatings to aid in seedling establishment. We conducted a greenhouse study on biochar and deactivated yeast use as seed coatings, assessing germination, establishment, and early growth of white clover (Trifolium repens) and purple prairie clover (Dalea purpurea). Coated seeds were applied to a mine tailing, a coarse granitic sand, and potting soil mix substrates; seedling establishment and growth were monitored over 75 days. Biochar coatings enhanced the seedling establishment of Trifolium, with biochar and biochar plus yeast coatings giving the best results. In some cases, these effects persisted throughout the experiment: biochar coatings resulted in a ~fivefold increase in Trifolium biomass at harvest for plants in the potting soil mix but had neutral effects on sand or tailings. Biochar seed coatings also enhanced Dalea germination in some cases, but the benefits did not persist. Our results indicate that biochar-based seed coatings can have lasting effects on plant growth well beyond germination but also emphasize highly species-specific responses that highlight the need for further study. Full article

The paper presents a comparative study of the erosion wear resistance of WC-10Co4Cr, Cr₃C₂-25NiCr and martensitic stainless steel (SS) coatings deposited onto an AlSi7Mg0.3 (Al) alloy substrate by high-velocity air‒fuel (HVAF) spraying. The influence of the abrasive type (quartz sand or granite gravel), erodent attack angle, thickness, and microhardness of the coatings on their and Al substrate’s wear resistance was comprehensively investigated under dry erosion conditions typical for fan blades. The HVAF-spraying process did not affect the Al substrate’s structure, except for when the near-surface layer was 20‒40 μm thick. This was attributed to the formation of a modified Al-Si eutectic with enhanced microhardness and strength in the near-substrate area. Mechanical characterization revealed significantly higher microhardness values for the cermet WC-10Co4Cr (~12 GPa) and Cr₃C₂-25NiCr (~9 GPa) coatings, while for the SS coating, the value was ~5.7 GPa. Erosion wear tests established that while Cr₃C₂-25NiCr and SS coatings were more sensitive to abrasive type, the WC-10Co4Cr coating exhibited significantly higher wear resistance, outperforming the alternatives by 2‒17 times under high abrasive intensity. These findings highlight the potential of HVAF-sprayed WC-10Co4Cr coatings for extending the service life of AlSi7Mg0.3-based fan blades exposed to erosion wear at normal temperatures. Full article

It is very important to clarify the optimization method of the rock-like material ratio for accurately characterizing mechanical properties similar to the original rock. In order to explore the optimal ratio of rock-like materials in gneissic granite, the water–paste ratio, iron powder content and coarse sand content were selected as the influencing factors of the ratio. An orthogonal test design and sensitivity analysis of variance were used to obtain the significant influencing factors of the ratio factors on seven macroscopic mechanical parameters, including compressive strength σ_c, tensile strength σ_t, shear strength τ_f, elastic modulus E, Poisson’s ratio ν, internal friction angle φ and cohesion c. A multivariate linear regression equation was constructed to obtain the quantitative relationship between the significant ratio factors and the macroscopic mechanical parameters. Finally, a rock-like material ratio optimization program based on genetic algorithm inversion was written. The results show that the water–paste ratio had extremely significant effects on σ_c, σ_t, τ_f, E, ν and c. The iron powder content had a highly significant effect on σ_c, σ_t, τ_f and c, and it had a significant effect on ν and φ. Coarse sand content had a significant effect on σ_c, E and c. The multiple linear regression model has good reliability after testing, which can provide theoretical support for predicting the macroscopic mechanical parameters of rock-like materials to a certain extent. After testing, the ratio optimization program works well. When the water–paste ratio is 0.5325, the iron powder content is 3.975% and the coarse sand content is 15.967%, it is the optimal ratio of rock-like materials. Full article

The slope erosion in the distribution area of completely weathered granite is often relatively severe, causing serious ecological damage and property loss. Ecological restoration is the most effective means of soil erosion control. Taking completely weathered granite backfill soil as the research object, two types of slope protection plants, Vetiver grass and Pennisetum hydridum, were selected. We analyzed these two herbaceous plants’ soil reinforcement and slope protection effects through artificial planting experiments, indoor simulated rainfall experiments, and direct shear tests. The test results showed that the runoff and sediment production rates of the two herbaceous plant slopes were significantly lower than those of the bare slope, with the order of bare slope > Vetiver grass slope > Pennisetum hydridum slope. Compared with the bare slope, the cumulative sediment production of the Vetiver grass slope at 60 min decreased by 56.73–60.09%, and the Pennisetum hydridum slope decreased by 75.97–78.45%. The indoor direct shear test results showed that soil cohesion decreases with increasing water content. As the root content of Vetiver grass roots increases, soil cohesion first increases and then decreases, reaching a maximum value when the root content is 1.44%. As the root content of Pennisetum hydridum increases, soil cohesion increases. The internal friction angle increases slightly with increasing water content, while the root content does not significantly affect the internal friction angle. Therefore, the shear strength of soil decreases when the water content increases. The shear strength of the Vetiver grass root-soil composite reaches a peak at a root content of 1.44%, while the shear strength of the giant king grass root-soil composite increases as the root content increases. At the same root content, the shear strength of the Vetiver grass root-soil composite is slightly higher than that of giant king grass. The reinforcement effect of roots on shallow soil is better than on deep soil. Both herbaceous plants have an excellent soil-fixing and slope-protecting impact on the fully weathered granite backfill slope. Pennisetum hydridum’s soil and water conservation effect is significantly better than that of the Vetiver grass. In contrast, Vetiver grass roots slightly outperform Pennisetum hydridum in enhancing the shear strength of the soil. The research results can provide a theoretical basis for the vegetation slope protection treatment of fully weathered granite backfill slopes. Full article

Radon in soil poses a significant health risk when it accumulates inside dwellings. The estimation of radon potential is a difficult task due to the complex dynamics of radon within soil and its relations with the weather. This research focuses on the variability of radon activity, driven by environmental changes, assessed in two loam soils (loamy sand–granite soil and silty clay loam-calcareous soil) with different radium contents. We conducted an experiment with teow soil columns in a semi-controlled outdoor laboratory, in a warm semi-arid climate. We also examined the consequences of abundant rainfall on radon activity through artificial soil water content (SWC) experiment conditions. Statistical analyses reveal that SWC is the most significant parameter influencing radon activity in these experiments. Radon is proportional to SWC and inversely proportional to temperature, evapotranspiration, and pressure in both soils, while wind is negatively related only in the loamy sand soil. Based on our findings, we modelled radon potential considering different soils and climatic contexts. SWC influences radon potential by changing radon emanation, activity, and permeability, depending on the local soil texture and radium concentration. Full article

The growing interest in the use of building materials with a reduced carbon footprint was the aim of this research assessing the impact of four different types of low-emission cements on the properties of cement concretes used for the construction of local roads. This research work attempted to verify the strength characteristics and assess the durability of such solutions, which used the commonly used CEM I 42.5 R pure clinker cement and three multi-component cements: CEM II/A-V 42.5 R, CEM III/A 42.5 N-LH/HSR/NA, and CEM V/A S-V 42.5 N-LH/HSR/NA. Cement was used in a constant amount of 360 kg/m³, sand of 0/2 mm, and granite aggregate fractions of 2/8 and 8/16 mm. This research was carried out in two areas: the first concerned strength tests and the second focused on the area of assessing the durability of concrete in terms of frost resistance F150, resistance to de-icing agents, water penetration under pressure, and an analysis of the air entrainment structure in concrete according to the PN EN 480-11 standard. Analyzing the obtained test results, it can be concluded that the highest compressive strength of more than 70 MPa was obtained for CEM III concrete, 68 MPa for CEM V concrete, and the lowest for CEM I cement after 90 days. After the durability tests, it was found that the smallest decrease in compressive strength after 150 freezing and thawing cycles was obtained for CEM III (−0.9%) and CEM V (−1.4%) concretes. The high durability of concrete is confirmed by water penetration tests under pressure, because for newly designed recipes using CEM II, CEM III, and CEM V, water penetration from 17 mm to 18 mm was achieved, which proves the very high tightness of the concrete. The assessment of the durability of low-emission cements was confirmed by tests of resistance to de-icing agents and the aeration structure performed under a microscope in accordance with the requirements of the PN-EN 480-11 standard. The obtained analysis results indicate the correct structure and minimal spacing of air bubbles in the concrete, which confirms and guarantees the durability of concrete intended for road construction. Concretes designed using CEM V cement are characterized by a carbon footprint reduction of 36%, and for the mixture based on CEM III, we even observed a decrease of 39% compared to traditional concrete. Concrete using CEM II, CEM III, and CEM V cements can be successfully used for the construction of local roads. Therefore, it is necessary to consider changing the requirements of the technical specifications recommended for roads in Poland. Full article

The production of manufactured sand and stone processing can cause dust pollution due to the generation of a significant amount of stone powder. This dust (mainly granite powder) was collected and incorporated as a cement replacement into mass-manufactured sand concrete in order to enhance the mechanical properties and microstructures. The heat of the hydration was measured by adding the granite powder into the cementitious material system. The mechanical properties, autogenous shrinkage, and pore structures of the concrete were tested. The results showed that the mechanical strength of the concrete increased first and then decreased with the increase in granite powder content. By replacing the 5% cement with the granite powder, the 28 d compressive and flexural strength increased by 17.6% and 20.9%, respectively. The autogenous shrinkage was mitigated by the incorporation of the 10% granite powder and decreased by 19.7%. The mechanism of the granite powder in the concrete was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP). The porosity decreased significantly within the 10% granite powder. A microstructure analysis did not reveal a change in the type of hydration products but rather that the granite powder played a role in the microcrystalline nucleation during the hydration process. Full article

Mountains composed of granite are generally regarded as stable geological formations. However, in Alpine and high-altitude mountains in the eastern part of the Tibetan Plateau, geological hazards such as collapses and landslides occur frequently due to the deterioration of granite mechanical properties caused by the freeze–thaw cycles. To investigate this phenomenon, a freeze–thaw cyclic mechanical test is conducted on granite from the Basu area, and the rock’s damage trend during the freeze–thaw process is analyzed through wave velocity and nuclear magnetic resonance (NMR) tests. The results indicated that the internal damage of granite increases and its wave velocity decreases significantly with increasing the freeze–thaw cycles, implying a decline in the rock’s integrity. Furthermore, the development pattern of the NMR T2 relaxation time distribution indicates that the crack size range of naturally weathered rock samples further increased after freeze–thaw cycles, whereas less-weathered rocks showed a more concentrated range of crack sizes. Triaxial compression tests conducted on rock samples after the freeze–thaw cycles showed that parameters such as the uniaxial compressive strength, elastic modulus, internal friction angle, and cohesion of the rock decreased with increasing freeze–thaw cycles, while a significant change of Poisson’s ratio was not observed. Based on the test data and theoretical analysis, a freeze–thaw damage constitutive model of the Basu granite can be established to simulate and predict the overall variation in rock stress and strain under various confining pressures and freeze–thaw cycles. Hopefully, the present study will provide useful guidance for research on the hazard mechanism and hazard prevention of granite sand-sliding slopes in the Basu area. Full article