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To explore the effect and mechanism of coir fiber on the performance of foamed concrete, the flexural performance test, pore characteristics and microstructure test of coir fiber foamed concrete with different content were carried out. First, Image-Pro Plus (image processing software) was used to study the pore morphology, porosity, average pore diameter, and pore roundness of CFFC with various fibers dosage (0, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%) by binarization processing method. Then, a total of eighteen specimens, divided into six groups, were used to investigate the effect of CF dosage on flexural strength, toughness, energy absorption, and failure patterns of FC through a three-point flexural test. Furthermore, the microscopic properties of coir fiber foamed concrete (CFFC) were observed by scanning electron microscope (SEM) and energy dispersive X-ray detector (XRD) to explain the influence mechanism of CF on FC flexural properties. According to the research, CF can affect the pore characteristics of CFFC and improve its flexural performance. When CF content is 1.5–2.0%, the porosity, diameter and roundness of CFFC have lower values of 68.6%, 1.96 mm and 1.29. After the fiber dosage reaches 1.5%, the CFFC failure mode changed to plastic damage, the flexural strength increased from 0.33 to 0.73 MPa, and the toughness energy absorption value was increased from 0.05 to 1.4 J. The optimum dosage of coir fiber is 2.0% for improving the flexural mechanical properties of FC. CF affects the process of hydration reaction of CFFC, but does not change the type of hydration product. However, the flexural performance of FC would decrease with excessive dosage of CF (> 2.0%) due to accelerating the formation of Ca(OH) 2 . CFFC can solve problems such as brittleness and easy cracking existing in traditional foamed concrete, and it can be used in the field of pavement engineering, foundation backfill and lightweight wall structure with CF dosage of 15–2.0%.

Based on the climatic and geological characteristics of the non-weight collapsible loess area, the paper analyses the cooperative working conditions of the concrete surface structure and the non-weight collapsible loess subgrade. The thesis uses coal gangue powder, fly ash, calcium carbide slag powder, and silica fume to modify the permeable concrete, and studies the unconfined compression test after the modification, the load ratio (cbr) test, and the eds-sem scanning electron microscope test. And other physical and mechanical properties. The experimental results prove that the modified soil with 30% calcium carbide slag powder after 28 days of curing has the best compressive performance, but has a heavier industrial peculiar smell; 30% silica fume and 30% silica fume are mixed the compressive performance of the modified soil with coal gangue powder is close; the compressive performance of the modified soil with 30% fly ash is relatively low. Among the four different admixtures in the test, the improved soil mixed with 30% calcium carbide slag powder and 30% concrete gravel has the best compressive effect, and the other three improved soils have similar effects. In the experiment, after four different admixtures were used to improve soil mixing and concrete crushed gravel, the bearing ratio of the modified soil obtained by mixing 30% calcium carbide slag powder and 30% concrete crushed gravel was the best and much higher than that of the other three materials. Scanning through the electron microscope, it was observed that the admixture had a greater effect on the adhesion of the soil foundation and the concrete gravel, which made the soil structure more stable.

This study addresses the growing need for sustainable construction materials by investigating the mechanical properties and behavior of palm fiber-reinforced cementitious composite (FRCC), a potential eco-friendly alternative to synthetic fiber reinforcements. Despite the promise of natural fibers in enhancing the mechanical performance of composites, challenges remain in optimizing fiber distribution, fiber–composite bonding mechanism, and its balance to matrix strength. To address these challenges, this study conducted extensive experimental programs using palm fiber as reinforcement, focusing on understanding the fiber–matrix interaction, determining the pullout load–slip relationship, and modeling fiber bridging behavior. The experimental program included density calculations and scanning electron microscope (SEM) analysis to examine the surface morphology and diameter of the fibers. Single fiber pullout tests were performed under varying conditions to assess the pullout load, slip behavior, and failure modes of the palm fiber, and a relationship between the pullout load and slip with the embedded length of the palm fiber was constructed. A trilinear model was developed to describe the pullout load–slip behavior of single fibers, and a corresponding palm-FRCC bridging model was constructed using the results from these tests. Section analysis was conducted to assess the adaptability of the modeled bridging law calculations, and the analysis result of the bending moment–curvature relationship shows a good agreement with the experimental results obtained from the four-point bending test of palm-FRCC. These findings demonstrate the potential of palm fibers in improving the mechanical performance of FRCC and contribute to the broader understanding of natural fiber reinforcement in cementitious composites.

To study the effect of periodic water circulation on rock mass, chlorite–amphibolite rocks from the slope of Nanfen open-pit iron mine in Liaoning province were chosen as the engineering samples and were investigated using uniaxial compressive experiment and scanning electron microscopy. The effect of different wetting and drying cycles on the mechanical properties and microstructure of the rocks was investigated. The characteristics of pore parameters from the SEM images were obtained by Image Pro Plus image processing software. The results show that with the increase in number of wetting and drying cycles, the uniaxial compressive strength of the rock decreases and the porosity increases significantly. The weakening of macroscopic mechanical properties of rocks is closely related to the changes in microstructures of rocks. The water–rock interaction changes the size, shape and porosity of the rock pores and then affects its mechanical properties. Based on the combination of macro and micro, quantitative analysis of the weakening process of rocks subjected to wet and dry cycles can provide a better reference index for evaluating the stability of geotechnical engineering.

With the rapid development of the subway rail transit, the effect of the cyclic loading on the surrounding foundations and buildings has drawn wide attention. In addition to the in situ tests and the laboratory triaxial tests, microscopic tests also provide an effective way to clarify the physical and mechanical characteristics of soils. On the other hand, the characteristics of the soft silty clay before and after freezing–thawing has been less studied. In this paper, the scanning electron microscope (SEM) tests following the cyclic triaxial tests of silty clay layer were performed to investigate the variations of the microscopic pore structures of the layer before and after freezing–thawing. The corrected Otsu method was used to obtain the binary SEM images of silty clay. The porosity results demonstrate that the magnifications from 1000× up to 5000× were suitable for observation of the silty clay microstructures. The binary SEM images of soil pore structures were quantitatively analyzed, including the porosity, the size distribution, the pore shape coefficient, the pore orientation distribution and the fractal dimension. The pore orientation of samples without loading is arranged in the horizontal direction, while the pores of samples under cyclic loadings are arranged in the vertical. After freezing–thawing, the mean anisotropy value of the microscopic pore structures increased about 12% and the porosity of samples without loadings increases about 11.24%. The lower the freezing temperature is, the larger the porosity within the samples becomes. However, the freezing–thawing has little effect on the pore shape coefficient of the silty clay. The porosity of the silty clay increases with an increase in pore diameter, but it decreases with the increase in excess pore pressure. In addition, the microscopic pore structures of the silty clay exhibit fractal characteristics. The fractal dimension is reduced by the disturbance from the effect of freezing–thawing, coupled with the effect of cyclic loading.

Increasing the deeper understanding of the thermal damages and failure mechanisms of sandstone undergoing thermal treatments at different temperatures is a key concern for deep-mining and underground coal gasification processes. In this research study, a scanning electron microscope (SEM) apparatus, JSM-5410LV, which was equipped with a built-in digital electro-hydraulic servo loading system, was applied to carry out a series of three-point bending tests on Pingdingshan sandstone following heat treatments at elevated and high temperatures ranging from 25 to 600 °C. The subcritical crack initiation load, peak load, and elastic modulus were found to increase with the increases in the thermal treatment temperatures until a maximum was achieved at 125 °C, after which decreases were observed. However, it should be noted that there were sudden drops observed for the specimens after the thermal treatment temperature reached 150 °C due to the thermal diffusivity of the cement. The subcritical crack growth length was theoretically calculated, and a digital speckle correlation method (DSCM) was applied to verify the initial load and subcritical crack growth length. It was found that the fracture toughness fluctuated significantly when the thermal treatment temperature ranged from 25 to 125 °C, and reached a peak of 47.45 MPa mm0.5. It was also observed that, as the temperature was raised from 175 to 600 °C, the fracture toughness gradually decreased. The subcritical crack growth mode was determined to be intra-granular cracking following the thermal treatments below 125 °C, while a mixture of intra-granular and trans-granular cracking occurred in the specimens which experienced thermal treatments of 175 °C. The relationship between heat treatment temperature and subcritical crack growth was derived, which could be used to develop geothermal energy extraction from the critical temperature resources.

A bio-based reinforcement strategy was studied as a means to overcome the inherent weaknesses of thermoplastic cassava starch (TPCS), namely its low mechanical strength and high susceptibility to moisture. Candelilla wax, a natural hydrophobic additive, was incorporated into TPCS at different loadings (0, 2.5, 5, 7.5, and 10 wt %) and processed via hot-press compression moulding. The fabricated composites were characterised to examine the effects of wax addition on their mechanical, thermal, and moisture-resistance performance. Mechanical tests (tensile, flexural, and impact), with scanning electron microscopy (SEM), thermogravimetric analysis (TGA). The incorporation of candelilla wax notably improved the material’s performance, particularly at 5 wt%, where tensile strength and modulus increased 77.4% and 615%, respectively. Flexural and impact strength also increased, indicating enhanced toughness. The SEM micrographs showed rougher fracture surfaces with increasing wax, while Fourier transform infrared spectroscopy (FT-IR) confirmed intermolecular hydrogen bonding between starch and wax. Improved thermal stability and reduced water sensitivity were also observed, with the 10 wt % wax composites exhibiting the lowest moisture absorption, solubility, and swelling. Overall, candelilla wax proved effective in strengthening TPCS both structurally and functionally, highlighting its potential for sustainable biodegradable materials in moisture-sensitive applications.

Bio-cementation of natural sand is a prospective solution to improve their engineering properties. The enhancement of strength and low-strain shear modulus is considered to be of high engineering significance for improvement in the performance of sand under both static and dynamic loading. In the present study, bio-cementation effects of bacillus Sporosarcina pasteurii bacteria on standard Ennore sand of India are studied at the microstructure level through scanning electron microscope (SEM) investigation considering microbial-induced calcite precipitation (MICP) technique. The crystallographic structure of the bio-cemented sand is reported through X-ray diffraction (XRD) analyses. Stress–strain behaviour and improvement in the strength of bio-cemented sand with different pore volumes of cementation solution have been investigated through unconfined compression strength (UCS) testing. Finally, the shear wave velocity values of the bio-cemented sand are assessed through bender element testing for different confining pressures, and low-strain shear modulus values have arrived. The study is believed to be helpful in the quantification of improvement of strength and low-strain shear modulus values of bio-cemented sand.

Nowadays, fibrous minerals pose as significant health hazards to humans, and exposure to these fibers can lead to the development of severe pulmonary diseases. This work investigated the morphology, crystal structure, chemistry, and surface activity of fibrous ferrierite recently found in northern Italy through an integrated approach using scanning electron microscopy–energy dispersive spectroscopy, electron microprobe, inductively coupled plasma atomic emission spectrometry, X-ray powder diffraction, and electron paramagnetic resonance. Our results show that a notable amount of ferrierite fibers are breathable (average length ~22 µm, average diameter 0.9 µm, diameter-length ratio >> 1:3) and able to reach the alveolar space (average Dae value 2.5 μm). The prevailing extra-framework cations are in the Mg > (Ca ≈ K) relationship, R is from 0.81 to 0.83, and the Si/Al ratio is high (4.2–4.8). The bond distances suggest the occurrence of some degree of Si,Al ordering, with Al showing a site-specific occupation preference T1 > T2 > T3 > T4. Ferrierite fibers show high amounts of adsorbed EPR probes, suggesting a high ability to adsorb and interact with related chemicals. According to these results, fibrous ferrierite can be considered a potential health hazard, and a precautionary approach should be applied when this material is handled. Future in vitro and in vivo tests are necessary to provide further experimental confirmation of the outcome of this work.