Explore the vast range of titles available.

Manufactured sand concrete (MSC) has increasingly applied in engineering. However, how to enhance the thermal crack resistance of MSC has not clearly studied yet, which limits the wide applications of manufactured sand in engineering. We have adopted the method of mixing limestone powder (LP) to make MSC with four mass fractions (wt.%) of 5%, 10%, 15%, and 20% of LP content, designed the mix proportion of concrete, tested their mechanical properties, observed their microstructure by scanning electron microscopy (SEM) and investigated the effect of LP on anti-cracking performance using temperature stress testing machine (TSTM). These findings reveal that the mechanical properties and thermal crack resistance of 15% LP MSC are the best. Our results also provide a research basis for the MSC to be widely used in engineering.

In recent years, the reinforcement of calcareous sands using the microbially induced calcium carbonate precipitation (MICP) method has emerged as a prominent research area. Nevertheless, a significant drawback of the MICP method is that multiple treatments with the cementing solution are required to achieve the desired improvement effect. To address this limitation, this study proposes an optimized MICP strategy through adding the ferric ion into cementing solutions. The effectiveness of the proposed method was investigated by analyzing the precipitation of CaCO 3 , unconfined compressive strength (UCS) and permeability coefficient through aqueous solution test and sand column reinforcement test. Experimental results revealed that ferric ion incorporation significantly altered CaCO 3 crystal morphology and particle size distribution in aqueous solution test. In sand column tests, specimens treated with cementing solution with ferric ion achieved the UCS of 2.83 MPa after five injection cycles, representing a 15-fold increase compared to conventional MICP-treated specimens under the same test conditions. At the same time, permeability coefficients decreased by two orders of magnitude relative to untreated sand. The micro-structure analysis showed that ferric ions were involved in the reaction to generate a clogging precipitate, which changed the distribution of bio-CaCO3 in the pores of the soil, thereby improving the cementation efficiency. These findings indicate that the addition of ferric ion can overcome the shortcoming of frequent treatment of cementing solution in MICP-reinforced calcareous sand, and provide new insights for the development of effective biological grouting strategies.

Sand production in oil wells is recognized as a persistent challenge during oilfield development, adversely affecting well productivity and operational stability. Chemical sand control methods, particularly resin-based sand consolidation, are considered a promising solution due to their operational simplicity and effectiveness. However, conventional emulsified resins are known to be highly sensitive to high-salinity environments, which can lead to emulsion destabilization and reduced consolidation strength. To address this limitation, a novel emulsified epoxy resin system was developed in this study using a nonionic emulsifying curing agent—fatty amine poly(epoxy ethyl ether)—by which salinity tolerance is significantly enhanced, supporting dilution water salinity up to 3.8 × 10⁴ mg/L. Through single-factor experiments, an optimal formulation was identified as 16% epoxy resin, 24% emulsified curing agent, 1% coupling agent, and 5.6% stabilizer. The molecular structure of the emulsified resin and the stability of the cured matrix were thoroughly characterized. The effects of curing temperature, time, sand particle size, and stabilizer dosage on compressive strength and permeability were systematically evaluated. It was demonstrated that after being cured at 80 °C for 12 hours, the consolidated cores achieved a compressive strength exceeding 3 MPa with permeability retention above 75%. Furthermore, the consolidated cores were shown to exhibit excellent long-term stability, maintaining their mechanical and flow properties after 30-day immersion in kerosene, 10% HCl, and formation water. This study bridges a critical research gap in high-salinity applications of water-based resin emulsions and provides a robust technical solution for sand control in challenging reservoir environments.

Sand production poses a major challenge in offshore heavy oil development, leading to casing erosion, equipment damage, and wellbore instability, which ultimately results in production decline. Conventional mechanical and chemical sand control methods often exhibit limited effectiveness in fine-grained or high-salinity formations and may induce formation damage or high operational costs. This study developed a self-generated foam-resin composite sand consolidation system to address these issues. The system integrated a controllable gas-generating subsystem and a melamine-formaldehyde (MF) resin matrix, thus enabling in-situ foam generation and sand consolidation. Laboratory experiments were conducted in three stages: optimization of gas and foaming agent subsystems, formulation and evaluation of the resin-based consolidant, and integration testing of the composite system. The optimized formulation resulted in controllable gas production, high foam stability, and consolidated sand cores with compressive strength >7 MPa. The system exhibited thermal stability up to 90 °C, salinity resistance, moderate permeability (~4 μm2), non-adhesion to metal surfaces, and negligible sand production (<0.1%) under dynamic water flooding. These results indicate that the foam-resin composite system provides an efficient, environmentally compatible, and cost-effective solution for sand control in complex offshore heavy oil reservoirs.

Desertification and wind erosion in arid regions demand sustainable solutions beyond conventional methods. This study investigates the efficacy of Microbially Induced Carbonate Precipitation (MICP) for sand stabilization in the Taklimakan Desert, employing Sporosarcina pasteurii to induce calcium carbonate crust formation. Field trials on man-made dunes and trapezoidal sandy land applied bacterial and cementation solutions (urea, calcium chloride, nutrients) in varying frequencies (1–8 spray cycles). Comprehensive evaluations included bearing capacity tests, wind erosion measurements (erosion pins), crust thickness analysis, and permeability assessments, supported by SEM, XRD, and EDS to elucidate microstructural changes. Results demonstrate that MICP treatment significantly enhances surface stability, achieving bearing capacities of 346.67 kPa (trapezoidal land) and 298.67 kPa (dunes) while reducing wind erosion by 95% (from 100.56 mm to < 5.06 mm). Crust thickness reached 21.02 mm, with SEM revealing dense CaCO₃ networks filling > 90% of interparticle pores. The treatment’s environmental resilience was validated through dry-wet cycle tests (5 cycles, < 2.9% mass loss) and reduced permeability (1.2 × 10⁻⁴ cm/s), confirming its durability under fluctuating climatic conditions. The 8-spray-cycle protocol emerged as optimal, leveraging sequential bioaugmentation and biostimulation to maximize calcite precipitation. These findings position MICP as a scalable, eco-friendly alternative to traditional methods, offering superior mechanical performance, environmental compatibility, and long-term viability for desertification mitigation in arid ecosystems.

The integration of palm fiber with Microbially Induced Calcite Precipitation (MICP) technology offers a sustainable and bio-based approach to enhance the mechanical performance and durability of sandy soils, particularly under freeze-thaw conditions. In this study, a systematic experimental investigation examines the effects of varying palm fiber contents (0%−0.30%) on the bearing capacity, crust thickness, calcium carbonate deposition, and freeze-thaw resistance of MICP-treated sand. Results indicate that mechanical performance improves with increasing fiber content, peaking at 0.15%, beyond which the benefits diminish due to fiber agglomeration. At the optimal dosage, the bearing capacity increases by 24%, crust thickness by 70.5%, and calcium carbonate content reaches 16.8% compared to fiber-free MICP samples. Freeze-thaw tests demonstrate higher mass and strength retention, indicating improved durability. Microstructural analyses using SEM, XRD, EDS, and FTIR reveal enhanced microbial attachment and uniform CaCO₃ precipitation along fiber-sand interfaces, which strengthens matrix cohesion. These findings uncover a hybrid bio-mechanical reinforcement mechanism and highlight the trade-offs between fiber dosage and pore connectivity. This study provides novel insights into fiber-assisted biomineralization and offers a viable pathway for environmentally friendly soil reinforcement. Furthermore, potential directions such as predictive modeling, biodegradability assessments, and field-scale application are proposed to support long-term geotechnical and ecological engineering deployment.

The present study describes the production of biosurfactant from isolate B. licheniformis Ali5. Seven different, previously-reported minimal media were screened for biosurfactant production, and two selected media were further optimized for carbon source. Further, various fermentation conditions such as (pH 2–12, temperature 20–50 °C, agitation speed 100–300 rpm, NaCl (0–30 g·L−1) were investigated. The partially purified biosurfactant was characterized by Fourier transform infrared spectroscopy (FTIR) and matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS) and found a lipopeptide mixture, similar to lichenysin-A. Biosurfactant reduced surface tension from 72.0 to 26.21 ± 0.3 and interfacial tension by 0.26 ± 0.1 mN·m−1 respectively, biosurfactant yield under optimized conditions was 1 g·L−1, with critical micelle concentration (CMC) of 21 mg·L−1 with high emulsification activity of (E24) 66.4 ± 1.4% against crude oil. Biosurfactant was found to be stable over extreme conditions. It also altered the wettability of hydrophobic surface by changing the contact angle from 49.76° to 16.97°. Biosurfactant efficiently removed (70-79%) motor oil from sand, with an efficiency of more than 2 fold as compared without biosurfactant (36–38%). It gave 32% additional oil recovery over residual oil saturation upon application to a sand-packed column. These results are indicative of potential application of biosurfactant in wettability alteration and ex-situ microbial enhanced oil recovery.

Microbially induced carbonate precipitation (MICP) is promising for soil stabilization. However, its large-scale application is hindered by the cost of laboratory-grade yeast extract (YE), which often accounts for more than 70% of cultivation medium expenses. Here, we evaluate two standardized industrial nitrogen sources—industrial yeast extract (IYE) and soy peptone (SP)—as complete or partial replacements for YE in Sporosarcina pasteurii cultivation. Urease activity and the performance of bio-cemented sand columns were assessed via unconfined compressive strength (UCS), CaCO 3 content, and mineralogical/microstructural analyses. Results indicated that the partial substitution scheme of 5 g/L pure YE + 10 g/L IYE yielded the best overall outcomes: bacterial urease activity reached ~80% of the control, UCS reached 4.27 MPa (9% higher than the control), and the nitrogen-source cost was reduced by 65.53%. The enhanced strength correlates with a favorable precipitation pathway that produced predominant calcite (~95.57% of the CaCO 3 precipitate), together with a dense, interlocking microstructure. In contrast, SP-substituted media produced lower UCS despite a high CaCO 3 content (up to 15.31%), indicating that mechanical performance depends not simply on the total amount or final polymorph of CaCO 3 , but on the combined effects of polymorph composition, precipitation pathway, and the resulting microstructural organization. Overall, the proposed YE–IYE blending strategy offers a practical route to lower-cost, higher-performance MICP sand stabilization.

To address the challenge of high permeability in coastal silty sand foundation pits, which is prone to seepage failure, this study investigated the improvement effects of three chemical stabilizers—sodium silicate, calcium lignosulfonate, and sodium polyacrylate—on the permeability characteristics of undisturbed silty sand using a self-designed seepage test system. The results demonstrated that the cumulative erosion mass of the untreated soil increased exponentially over time, with an erosion rate as high as 89.39 g/min. In contrast, the cumulative erosion mass of the silty sand treated with any of the three chemical stabilizers exhibited a trend of initial increase followed by stabilization, and the erosion rates were all reduced to below 30 g/min. Notably, under the conditions of 4% dosage and 6 hours of curing, sodium polyacrylate reduced the erosion rate to 3.98 g/min, limited the cumulative erosion mass to only 35 g, stabilized the permeability coefficient within the range of 10 ⁻ ⁶ to 10 ⁻ ⁷ cm/s, and shortened the permeability stabilization time to 6.3 minutes. Its improvement effect was superior to that of the other two stabilizers, meeting the anti-seepage requirements for high-standard cut-off walls. The research findings provide efficient and reliable chemical improvement solutions and a theoretical basis for anti-seepage engineering in foundation pits under complex coastal geological conditions.

The objective of this study is to assess the effectiveness of a novel structure comprising a geocomposite drainage layer and a thin sand layer (GDL + sand) in mitigating the rapid dumping of excavated clay and its associated issues, such as landslides. Two sets of direct shear tests were conducted to investigate the influence of sand layer thickness and compaction degree on the interface shear behavior of the GDL + sand structure. As the sand layer thickness increased, both the interface shear strength and friction angle gradually increased, first more sharply and then at a slower rate toward stability, while the interface cohesion decreased gradually. The optimal sand layer thickness for achieving the most effective reinforcement in stabilizing the clay was identified as 10 mm. A higher sand layer compaction degree was found to result in increased interface shear strength, interface friction angle, and interface cohesion. Building on these findings, the reinforcing efficiency of the GDL + sand structure was investigated through mechanism analysis in comparison to that of a geogrid + sand structure and GDL structure as per the interface friction coefficient. The ranking of interface friction coefficients among the three structures emerged as: geogrid + sand > GDL + sand > GDL. These results suggests that the GDL + sand structure exhibits superior reinforcement efficiency compared to the GDL structure and offers better drainage efficiency than the geogrid + sand structure.