This study investigated the impact of optimum dosages of nano-calcium carbonate (nano-CaCO3) and nanosilica on the engineering behavior of black cotton soil. The desired percentage of nano-addition, 2%, for both nanomaterials, was determined by analyzing the plasticity-compaction characteristics and the relative strength index values of treated samples. The study unveiled that the entire clay microstructure was transformed into a nanocrystalline matrix after treatment. The deviatoric strength enhancement with confining pressure and curing period was significant after treating the soil with either nano-CaCO3 or nanosilica. The nanosilica treatment was found to be more effective in improving the California bearing ratio (CBR) strength of black cotton soil samples compared with nano-CaCO3 stabilization. The addition of nanomaterials induced the formation of nanocrystalline hydrate gels and silica gel, resulting in an increased resistance to volumetric deformation under compressive stresses. The hydraulic conductivity of nano-treated samples dropped due to the highly tortuous networks between pores in the nano-crystalline structure. The experimental results were substantiated by analyzing the microstructure of nano-treated soils using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) techniques.

Transforming waste materials into valuable commodities is a promising strategy to alleviate challenges associated with managing solid waste, benefiting both the environment and human well-being. This study is focused towards harnessing the potential of waste eggshell microparticles (ESMP) (0.10, 0.15, 0.20 g/150 mL) as reinforcing biofiller and orange peel essential oil (OPEO) (14 %, 25 % and 36 %, w/w) as bioactive agent with pectin (2.80, 2.85, 2.90, and 3.00 g/150 mL) to fabricate five different biocomposite films using particle dispersion and solvent casting technique. The addition of ESMP and OPEO progressively increased film thickness and led to variations in transparency. Micromorphological analysis and vibrational spectroscopy indicated hydrophobicity and compactness, as showed by the loss of free O- H bonds, sharpening of aliphatic C- H and stretching of C = C, C- O and C- O- C bonds with increasing filler content. Noticeable improvements in thermal stability and tensile strength were observed, while the flexibility was minimized. The films displayed remarkable barrier properties against hydrological stress, as evidenced by a reduction in water activity, moisture content, water uptake capacity, and solubility. The antioxidant activity against DPPH radicals suggested efficient release of bioactive compounds. Antibacterial assessment revealed inhibitory effect on Staphylococcus aureus and Bacillus cereus. During soil burial, notable weight loss along with shrinkage confirmed the film biodegradability. In conclusion, the pectin-ESMP-OPEO biocomposite films show potential characteristics as food packaging materials, warranting further performance testing on food samples.

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.

Cementations bind sand/soil particles via physical and chemical interactions to form composite solids with macroscopic mechanical properties. While conventional cementation processes (e.g., silicate cement production, phosphate adhesive synthesis, and lime calcination) remain energy-intensive, bio-cementation based on ureolytic microbially induced carbonate precipitation (UMICP) has emerged as an environmentally sustainable alternative. This microbial-mediated approach demonstrates comparable engineering performance to traditional methods while significantly reducing carbon footprint, positioning it as a promising green technology for construction applications. Nevertheless, three critical challenges hinder its practical implementation: (1) suboptimal cementation efficiency, (2) uneven particle consolidation, and (3) ammonia byproduct emissions during ureolysis. To address these limitations, strategic intervention in the UMICP process through polymer integration has shown particular promise. This review systematically examines polymer-assisted UMICP (P-UMICP) technology, focusing on three key enhancement mechanisms: First, functional polymers boost microbial mineralization efficacy through multifunctional roles, namely microbial encapsulation for improved survivability, calcium carbonate nucleation site provision, and intercrystalline bonding via nanoscale mortar effects. Second, polymeric matrices enable homogeneous microbial distribution within cementitious media, facilitating uniform bio-consolidation throughout treated specimens. Third, selected polymer architectures demonstrate ammonium adsorption capabilities through ion-exchange mechanisms, effectively mitigating ammonia volatilization during urea hydrolysis. Current applications of P-UMICP span diverse engineering domains, including but not limited to crack repair, bio-brick fabrication, recycled brick aggregates utilization, soil stabilization, and coastal erosion protection. The synergistic combination of microbial cementation with polymeric materials overcomes the inherent limitations of pure UMICP systems and opens new possibilities for developing next-generation sustainable construction materials.

High lime content in agricultural soils poses a significant challenge to crop production, particularly in viticulture. Due to the persistent and detrimental effects of lime stress on plant growth, the present study investigated the potential of iron oxide nanoparticles (Fe3O4-NPs) to mitigate lime-induced stress in 1103 Paulsen American grapevine rootstock. We examined the effects of Fe3O4-NPs (0, 0.01, 0.1, and 1 ppm) under varying lime stress conditions (0%, 20%, 40%, and 60% CaCO3). Our findings revealed that increasing lime content progressively inhibited grapevine growth, with significant reductions in shoot fresh weight, root fresh weight, shoot length, and leaf number. Fe3O4-NP application demonstrated pronounced protective effects: 0.1 ppm Fe3O4-NPs optimized growth under non-stressed conditions, while 1 ppm Fe3O4-NPs significantly improved plant performance under 60% lime stress. Notably, nanoparticle treatments mitigated oxidative stress by reducing membrane damage, lipid peroxidation, and leaf temperature while maintaining photosynthetic efficiency and osmotic balance. Fe3O4-NPs demonstrated significant potential in mitigating lime-induced stress in grapevines, with optimal concentrations of 0.1 ppm for low-moderate lime environments and 1 ppm for high lime content areas. These findings provide a targeted nanobiotechnological approach to enhance grapevine resilience in calcareous soils, advancing sustainable viticulture strategies.

Desertification is a global environmental issue that significantly threatens ecosystem stability and vegetation restoration in arid regions. This study proposes a multiple treatment strategy combining Artemisia sphaerocephala Krasch. gum (ASKG) with Enzyme-Induced Carbonate Precipitation (EICP) to enhance wind erosion control and seed germination. The effects of this approach were evaluated through field experiments. The results showed that single EICP treatment improved soil water retention and surface strength. However, high-concentration EICP treatment (>= 0.2 mol/L Cementation Solution, CS) induced salt stress, which suppressed plant survival. In contrast, when low-concentration EICP (0.1 mol/L CS) was combined with ASKG, a stable crust formed, improving surface strength and crust thickness, while preventing damage to the crust during early plant growth. The addition of 1.0 g/L ASKG reduced wind erosion depth by 67%, increased average moisture content to 7.4%, and promoted better seed germination, showing strong ecological compatibility and long-term stability. Furthermore, the second EICP treatment optimized the soil pore structure by adding CaCO3 precipitates, which increased average moisture content to 10.6% and increased surface strength by 114.5%. Microstructural analysis revealed that ASKG formed film or mesh structure around CaCO3 crystals, enhancing soil wind erosion resistance and water retention. Overall, the findings suggest that the multiple treatment strategy of EICP combined with ASKG successfully overcomes the ecological limitations of traditional high-concentration EICP, providing a sustainable solution for wind erosion control and vegetation restoration in desert areas.

The impact of four distinct calcium sources on the microbial solidification of sand in the Kashi Desert, Xinjiang, was investigated. A wind tunnel test over a 60-day period revealed the cracking behavior of four different complex calcium nutrient solutions. By comparing the bearing capacity and the results from dry-wet cycling and freeze-thaw cycle tests, it was concluded that the sample treated with calcium gluconate exhibited superior sand fixation performance, whereas the sample treated with calcium acetate showed weaker sand fixation effects. The microstructure of the treated sand samples was analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Elemental analysis was conducted via energy dispersive spectroscopy (EDS), and functional groups were identified through Fourier transform infrared spectroscopy (FTIR). These experimental findings hold significant implications for soil remediation, pollutant removal in soil, enhancement of soil fertility, and desert soil stabilization.

Bio-cement is a green and energy-saving building material, which has received wide attention in the field of ecological environment and geotechnical engineering in recent years. The aim of this study is to investigate the improvement effect of plant-based bio-cement (PBBC) in synergistic treatment of sand with organic materials, to highlight the effective use of tap water in PBBC, and to analyze the crack evolution pattern during the damage of specimens by using image processing techniques. The results showed that tap water can be used as a solvent for PBBC instead of deionized water. The characteristic trend of urease solutions prepared at different temperature environments was obvious, and the activity value of urease solution with low concentration is positively correlated with the ambient temperature, although the activity value is not high, it is not easy to inactivate. The incorporation of organic materials increased the peak stress up to 1809.30 kPa compared to the specimens modified only by PBBC. The damage of the specimens under uniaxial compression consisted of four stages: compaction, elastic deformation, pre-peak brittle damage and post-peak macroscopic damage. The corresponding crack evolution is the interpenetration of small-sized cracks into large-sized main cracks. The large-sized main cracks transform into penetration cracks before damage, and the small-sized cracks are distributed around the penetration cracks. The crack evolution parameters obtained by MATLAB processing are positively correlated with the strain.

In this research, the microbial-induced carbonate precipitation (MICP) technique combined with cement was proposed to improve the physical and mechanical properties of silt. A series of comparative experiments of the MICP technique combined with cement treatments on silt (MICP-reinforced soil-cement) were conducted. The unconfined compressive strength (UCS), internal friction angle, cohesive force, and ultrasonic velocity of the silt treated with the MICP technique combined with cement were higher than those treated with cement. The X-ray diffraction (XRD) and scanning electron microscope (SEM) tests showed that the cement hydration products cemented the silt into agglomerates and formed a skeleton, and the calcite produced by the MICP process covered the surface of the agglomerates and filled the silt pores and cemented the particles, which played a role in increasing the strength of the specimens. In addition, the products and reactants of MICP accelerated the hydration reaction of the cement and played a role in the curing system consistent with carbonate-based and alkaline earth metal-based early-strengthening agents. The results of this study will provide basic theoretical and experimental data for the research and application of microbe-based treatment approaches for silt.

Microbially induced calcium carbonate precipitation (MICP) is an emerging ecofriendly microbial engineering technique that utilizes urease-producing microorganisms to enhance the mechanical properties of soils. Sporosarcina pasteurii (S. pasteurii) stands out among these microorganisms as an efficient urease producer. However, field trials often lead to less-than-optimal experimental outcomes due to the presence of native soil microbes. To evaluate the impact of indigenous microorganisms on the effectiveness of MICP at the site, bacteria isolated from natural soil, classified of on-site low-ureolysis and high-ureolysis bacteria (OSLUB and OSHUB, respectively), were combined with S. pasteurii to conduct MICP experiments both in microfluidic chips and sand columns. Analysis covered the bacterial population, urease activity, pH changes, calcium carbonate crystal count and volume, as well as the unconfined compressive strength (UCS) of reinforced samples. Experimental results revealed that combining OSLUB with S. pasteurii led to a reduction in bacterial activity of 74% to 84% by 120 h, resulting in an approximately 60% decrease in the chemical conversion rate and the UCS of MICP-treated soils was 60% lower than the S. pasteurii. However, when OSHUB is mixed with S. pasteurii, although there is a reduction in bacterial activity by 49% to 54% by the 120-h mark, the decrease remains less pronounced than the activity decrease observed in S. pasteurii alone, which is 64%. Consequently, the rates of calcium carbonate chemical conversion were enhanced by 9% to 45%, and the UCS of the reinforced sand columns showed a slight improvement relative to the control group. This research highlights the distinct impacts of OSLUB and OSHUB on the efficiency of MICP on location. The main difference between OSLUB and OSHUB lies in their respective effects on pH levels following mixing. OSLUB tends to decrease the pH level gradually in the combined bacterial environment, while OSHUB, in contrast, increases the pH level over time in the same setting. The maintenance of both high bacterial activity and high precipitation rates is crucially dependent on pH levels, highlighting the importance of these findings for enhancing MICP efficiency in field applications. Strategies that either diminish the presence of OSLUB while augmenting that of OSHUB, or that sustain a relatively high pH level, could be valuable. These avenues promise significant improvements and merit further investigation in future studies.