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Dust is an environmental and health hazard. In this study, a new technology for dust suppressant is introduced using soybean urease with an optimal cementing solution. Calcium carbonate is produced by soybean urease and cementing solution, which bonds the soil particles towards a dust suppressant. A laboratory wind tunnel test is carried out to examine its effectiveness and discover possible optimization solutions. Several factors, including soybean meal concentration, cementing solution concentration, and volume of solution per unit area, are examined to quantify their influences on soil transport mass, evaporation ratio, evaporation rate, surface strength, water retention ratio, and infiltration rate of soil treated by different dust suppressants. Field tests are conducted to explore the performance of this method in the natural environment. The results show that compared with other dust suppressants, the optimized soybean urease has the smallest evaporation rate, a moderate infiltration rate, the largest water retention ratio and surface strength. The indexes of soybean urease for dust suppressant are found to be better than traditional materials. In the natural environment, soybean urease has a stronger anti-disturbance ability. This study concludes that soybean urease dust suppressant has great application potential as a cheap and green method. [ABSTRACT FROM AUTHOR]

Wind erosion is one of the significant natural calamities worldwide, which degrades around one-third of global land. The eroded and suspended soil particles in the environment may cause health hazards, i.e. allergies and respiratory diseases, due to the presence of harmful contaminants, bacteria, and pollens. The present study evaluates the feasibility of microbially induced calcium carbonate precipitation (MICP) technique to mitigate wind-induced erosion of calcareous desert sand (Thar desert of Rajasthan province in India). The temperature during biotreatment was kept at 36 °C to stimulate the average temperature of the Thar desert. The spray method was used for bioaugmentation of Sporosarcina (S.) pasteurii and further treatment using chemical solutions. The chemical solution of 0.25 pore volume was sprayed continuously up to 5 d, 10 d, 15 d, and 20 d, using two different concentration ratios of urea and calcium chloride dihydrate viz 2:1 and 1:1. The biotreated samples were subjected to erosion testing (in the wind tunnel) at different wind speeds of 10 m/s, 20 m/s, and 30 m/s. The unconfined compressive strength of the biocemented crust was measured using a pocket penetrometer. The variation in calcite precipitation and microstructure (including the presence of crystalline minerals) of untreated as well as biotreated sand samples were determined through calcimeter, scanning electron microscope (SEM), and energy-dispersive X-ray spectroscope (EDX). The results demonstrated that the erosion of untreated sand increases with an increase in wind speeds. When compared to untreated sand, a lower erosion was observed in all biocemented sand samples, irrespective of treatment condition and wind speed. It was observed that the sample treated with 1:1 cementation solution for up to 5 d, was found to effectively resist erosion at a wind speed of 10 m/s. Moreover, a significant erosion resistance was ascertained in 15 d and 20 d treated samples at higher wind speeds. The calcite content percentage, thickness of crust, bulk density, and surface strength of biocemented sand were enhanced with the increase in treatment duration. The 1:1 concentration ratio of cementation solution was found effective in improving crust thickness and surface strength as compared to 2:1 concentration ratio of cementation solution. The calcite crystals formation was observed in SEM analysis and calcium peaks were observed in EDX analysis for biotreated sand.

Wind-induced soil erosion is a major global misfortune, which obliterates nearly one-third of worldwide soil. The windswept sand particles cover large areas including highways, and make the visibility vague. This results in accidents, damaged infrastructure, delayed flights, and various health issues. The erosive impact of the wind can be minimized by enhancing the intactness of the soil surface. There is a prerequisite to adopt viable measures to strengthen soil against wind erosion. There are certain nature-based solutions that can fortify soil against wind erosion and the application of biopolymers is one of them. The objective of this study is to examine the viability of non-toxic biopolymers for stabilizing desert sand by improving its erosion resistance property and strength. In the present experiment, three biopolymers, sodium alginate (SA), pectin (P), and acacia gum (AG), were used with 1, 2, and 3% concentrations for 1 and 0.75 PV as stabilizing agents. The treatment with biopolymers was performed either by surficial treatment (spraying or pouring of solution) or by mixing and compact method based on the viscosity of prepared biopolymer solutions. The biotreated sand samples were tested in a wind tunnel at varying wind speeds of 10, 20, and 30 m/s to assess sand erosion. Surface strengths were assessed by measuring compressive strength using a pocket penetrometer. Crust thickness measurement was performed to check the penetration depth of biopolymer solution and binding of sand particles. All three biopolymers with 1% concentration gave a feasible solution for erosion against wind and binding of particles through SEM analysis. SA and P could not be sprayed for 2 and 3% concentrations due to high viscosity. This solution is also not feasible for the field application. Simultaneously, AG with 2 and 3% concentration was highly soluble, less viscous, and gave more surface strength due to higher percentage of biopolymer concentration. [ABSTRACT FROM AUTHOR]

Enzyme-induced carbonate precipitation (EICP) is a promising technique for soil reinforcement. To select a suitable calcium source and a suitable solution amount for aeolian sand stabilization using EICP, specimens treated with different solution amounts (1.5, 2, 2.5, 3, and 3.5 L/m2). Surface strength, crust thickness, calcium carbonate content (CCC) and water vapor adsorption tests were performed to evaluate the effect of two calcium sources (calcium acetate and calcium chloride) on aeolian sand solidification. The plant suitability of solidified sand was investigated by the sea buckthorn growth test. The suitable calcium source was then used for the laboratory wind tunnel test and the field test to examine the erosion resistance of solidified sand. The results demonstrated that Ca(CH 3 COO) 2 -treated specimens exhibited higher strength than CaCl 2 -treated specimens at the same EICP solution amount, and the water vapor equilibrium adsorption mass of Ca(CH 3 COO) 2 -treated specimens was less, indicating that Ca(CH 3 COO) 2 -solidified sand was more effective and had better long-term stability. In addition, plants grown in Ca(CH 3 COO) 2 -treated sand had greater seedling emergence percentage and higher average height, which indicated that calcium acetate is a more suitable calcium source for EICP treatment. Furthermore, the surface strength and crust thickness of solidified sand increased with increasing the solution amount. For sand treated with 3 L/m2 of solution, the excessive strength and thickness of the crust made plants growth difficult, and the performance of sand treated with more than 2 L/m2 of solution significantly improved. Thus, the solution amount of 2–3 L/m2 is suggested for engineering applications. The sand solidified using EICP in the field could effectively mitigate wind erosion and facilitate the growth of native plants. Therefore, EICP can be combined with vegetative method to achieve long-term wind erosion control in the future. • Calcium acetate is a more suitable calcium source for aeolian sand solidification using EICP. • The EICP solution amount of 2–3 L/m2 is suggested for engineering applications. • EICP can be combined with vegetative method to achieve long-term wind erosion control. [ABSTRACT FROM AUTHOR]

To realize the non-destructive detection of cultural relics, the limestone relics in Feilai Peak and Yue Temple area in Hangzhou, Chian were selected as inspection objects, and the relationship between the water absorption rate of limestone surface layer, ultrasonic longitudinal wave velocity and surface layer strength were investigated. The fitting model was established according to the variation characteristics among water absorption rate, ultrasonic longitudinal wave velocity, surface layer strength. The evaluation method of surface layer weathering level of limestone relics based on water absorption characteristics was also established based on the fitting model. Results show that the field test data of the superficial strength, longitudinal wave velocity and water absorption rate of limestone have an obvious negative correlation. The weathering grade evaluation method based on water absorption rate of rocks is derived from the field test data, and the rocks are classified into five grades: unweathered, slightly weathered, moderately weathered, strongly weathered and fully weathered. The corresponding water absorption rates range from 0-0.12%, 0.12-0.20%, 0.20-0.61%, 0.61-2.40% and >2.40%, respectively. The accuracy of the fitting results in the area around the seated statue of Luohan and the back of the Huangji tombstone are above 80%, so the weathering grade evaluation method is feasible. The weathering grade evaluation method is completely nondestructive and strictly conforms to the principle of minimum intervention. The conclusions obtained in this study can provide the reference for the subsequent conservation of limestone artifacts. [ABSTRACT FROM AUTHOR]

Microbial-induced calcium carbonate precipitation (MICP) is a new technology used for reinforcing soils through microbial mineralization. However, the existing MICP treatment technology is more suiTable for deeper soils due to its high permeability. In this study, HPMC, a cohesive material combined with Sporosarcina pasteurii-induced calcium carbonate precipitation was used to improve the surface layer of the soil. It was also tested in different contents of bacterial solutions and cementation solutions and with a different number of MICP treatments, and was analyzed and discussed by measuring the surface layer strength, calcium carbonate content generated in the crust, rainfall erosion resistance, wind erosion resistance, and ammonia retention rate of the specimens. The microstructure of the samples was investigated by XRD and SEM. It was shown that the addition of HPMC and increasing the number of MICP treatments were effective in the increase in the calcium carbonate content in the surface crust, but had no effect on the total amount of induced calcium carbonate. The combination of HPMC addition and MICP technology can effectively reduce rainwater scour loss and wind erosion loss, and increase its rainfall erosion resistance and wind erosion resistance. Rainfall losses were reduced by up to 30% in specimens treated with HPMC for MICP technology. When the wind speed was 12 m/s, the maximum mass loss rate of the specimens treated with HPMC for MICP was only 0.828%. The addition of HPMC can effectively improve the ammonia absorption rate and reduce the release of ammonia in the process of MICP technology, which is of great significance for environmental protection. The microstructure showed that the addition of HPMC and the increase in the number of treatments using MICP technology can make the surface structure of the specimens more compact, and the calcium carbonate can more effectively fill the pores and cement the soil particles, while the addition of HPMC may not change the calcium carbonate crystal type. [ABSTRACT FROM AUTHOR]

Microbial-induced calcium carbonate precipitation (MICP) is a new technology used for reinforcing soils through microbial mineralization. However, the existing MICP treatment technology is more suiTable for deeper soils due to its high permeability. In this study, HPMC, a cohesive material combined with Sporosarcina pasteurii-induced calcium carbonate precipitation was used to improve the surface layer of the soil. It was also tested in different contents of bacterial solutions and cementation solutions and with a different number of MICP treatments, and was analyzed and discussed by measuring the surface layer strength, calcium carbonate content generated in the crust, rainfall erosion resistance, wind erosion resistance, and ammonia retention rate of the specimens. The microstructure of the samples was investigated by XRD and SEM. It was shown that the addition of HPMC and increasing the number of MICP treatments were effective in the increase in the calcium carbonate content in the surface crust, but had no effect on the total amount of induced calcium carbonate. The combination of HPMC addition and MICP technology can effectively reduce rainwater scour loss and wind erosion loss, and increase its rainfall erosion resistance and wind erosion resistance. Rainfall losses were reduced by up to 30% in specimens treated with HPMC for MICP technology. When the wind speed was 12 m/s, the maximum mass loss rate of the specimens treated with HPMC for MICP was only 0.828%. The addition of HPMC can effectively improve the ammonia absorption rate and reduce the release of ammonia in the process of MICP technology, which is of great significance for environmental protection. The microstructure showed that the addition of HPMC and the increase in the number of treatments using MICP technology can make the surface structure of the specimens more compact, and the calcium carbonate can more effectively fill the pores and cement the soil particles, while the addition of HPMC may not change the calcium carbonate crystal type.

Heat treatment (HT) is thought to degrade wood surface wettability and cause gluing problems; this study focused on wettability and surface strength of the surface layer on heat-treated wood. The outer and inner surfaces formed by removing the 1-, 2- and 3-mm surface layers of heat-treated poplar on the tangential section were investigated. Dynamic wetting was analyzed according to the sessile drop method. The bonding failure models on different surfaces were also discussed based on both images of macro- and microscopic fracture interfaces. Using Fourier-transform near-infrared spectroscopy (FT-NIR), the cell wall chemistry on both outer and inner surfaces were analyzed. The results showed that the bonding strength of the outer surface was mainly affected by wettability, whereas the surface strength became the key factor for the inner layers. The removal of the first 1 mm of the surface layer enhanced the wetting process and transferred the failure mode from the glue line to the wood itself. FT-NIR revealed that the intensity of the thermal degradation on inner layers was alleviated with the removal depth; wettability and surface strength were enhanced compared with the outer surface. Surface abrasion and hardness declined, decreasing the surface strength and bonding capacity. This study indicates that the bonding of heat-treated wood is truly affected by the surface strength of the inner layers, in addition to the wettability on the outer surface. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Biodegradable surface sizing agent(poly-vinyl alcohol/itaconic acid/acrylamide)was synthesized via radical polymerization with MINITAB software'DOE. • PVA/IA/AM could form the hydrophobic coating layer with a spatial network structure on the surface of paper. • It not only improve the hydrophobicity of paper but also increase the paper surface strength. • The copolymer had better forming film characteristic and lower property of penetrating into the interior of paper than PVA. Abstract Biodegradable surface sizing agent(poly-vinyl alcohol/itaconic acid/acrylamide)was synthesized via radical polymerization with MINITAB software. Fourier transform infrared spectroscopy and scanning electron microscopy were used to evaluate the structure of the surface sizing agent. In the meantime, a thin layer of PVA or PVA/IA/AM was coated on the surface of paper. The strength and water resistance of paper were studied and compared. The optimization experiment condition for the surface sizing agent was determined by Design of Experiment (DOE). It indicated that PVA/IA/AM copolymer not only improve the hydrophobicity of paper but also increase the paper surface strength. It was attributed that PVA/IA/AM could form the hydrophobic coating layer with spatial network structure on the surface of paper and increase the number of hydrogen bonding between the copolymer and fiber. Furthermore, the copolymer had better forming film characteristic and lower property of penetrating into the interior of paper than PVA when they were coated on the surface of paper. [ABSTRACT FROM AUTHOR]

• Jack bean and soybean crude ureases were used for topsoil stabilization. • Organic matter in crude urease affected soil mechanical properties markedly. • Jack bean presented a greater potential in topsoil stabilization than soybean. • Optimum bean dosages were proposed at 40 g/L jack bean and 80 g/L soybean. • The cost of using crude ureases was greatly reduced compared to commercial urease. Enzyme-induced carbonate precipitation (EICP) is a prominent biogeotechnical technique for soil stabilization to address desert invasion and dust emission issues. This study investigates the bio-cementation efficacy of EICP mediated by jack bean crude urease (JCU) and soybean crude urease (SCU) on surface stabilization of aeolian sand from Tengger Desert. Topsoil properties of the EICP-treated sand including CaCO 3 , organic matter content, surface strength, and wind erosion resistance were evaluated. The urease activity of JCU was 3.4 times higher than SCU, resulting in a higher CaCO 3 content and surface strength of JCU-treated topsoil. The optimum bean dosages were observed at 40 g/L jack bean and 80 g/L soybean for achieving maximum CaCO 3 content and surface strength, respectively. EICP-treatments with excessive bean dosages would decrease the surface strength due to the interference of organic matter precipitation on effective bridging between the generated CaCO 3 crystals and the sand particles. Wind erosion resistance was evaluated under wind-sand flow condition at a wind speed of 13.8 m/s, which was positively correlated with surface strength. JCU presented an overall greater stabilization potential of topsoil than SCU. Additionally, the urease costs of EICP-treatments with JCU and SCU were reduced by about 380–1400 times compared with commercially available ureases. [ABSTRACT FROM AUTHOR]

Article presents the algorithm for obtaining maximum surface stresses for Novikov gears. Described surface strength calculation method is based on Hertz theory of two bodies being in point contact. What’s more the influence of gear position errors on maximum contact stresses has been presented. Also the comparison of Hertz stresses for Novikov and involute gears has been made.

A multifunctional fluorescent polymer based on coumarin (MFPC) was synthesized using a four-step synthetic route. To obtain the target compound, 7-amino-4-methylcoumarin, coumarin fluorescent monomer (CFM), and ultraviolet absorber monomer (UVAM) were prepared. By the reaction of CFM, UVAM, trimethyl-2-methacroyloxyethylammonium chloride (DMC), and acrylamide (AM) as a linker, a new multifunctional fluorescent polymer was synthesized. The structure of the MFPC was characterized by Fourier transform infrared (FTIR) and nuclear magnetic resonance (1H-NMR) spectroscopies. The optical properties of MFPC were measured by ultraviolet-visible (UV-vis) and fluorescence spectroscopies, in aqueous solution. The integration effect between MFPC and paper was tested by scanning electron microscopy. The application performance of MFPC on paper was evaluated by measuring the surface strength, smoothness, and whiteness using the printability tester and the UV accelerated aging test. Results indicated that the MFPC had good solubility in water. It also exhibited a positive effect on the light stability and surface strength of paper as a light stabilizer, fluorescent brightener, and surface sizing agent.

The surface strength and pore content in electron beam melted (EBM) Ti-6Al-4V alloy play a key role in its tribological performance and fatigue life. In this study, a novel surface electropulsing treatment was applied to generate local phase transformation strengthening on the surface of EBM Ti-6Al-4V while simultaneously repairing the pores in the hardened zone. The surface microhardness was enhanced by 36 % from ∼260 HV 0.2 to ∼355 HV 0.2 when electropulsing treated for 120 ms, and keep the hardness with the prolongation of time to 240 ms. The thickness of the hardened surface increased from 1.3 mm to 1.7 mm with the increase in processing time. In addition, the hardened zone showed much fewer pores than the matrix. Mathematical simulation indicated that the high cooling rate in the treated zone was sufficient to result in a martensite transformation, and the compressive stress induced by thermal stress and electrode loading could cause deformation and furtherly improve the strength. More importantly, the combination of the large-scale compressive stress with the current crowding effect induced compression in the hardened zone is a benefit for repairing the pore. Predictably, this novel electropulsing treatment can be extended to other AM α + β Ti alloy systems and AM martensite steel systems for strengthening and pore repair. • Electropulsing was proposed to improve the surface strength of the EBM Ti alloy. • Pores in the hardened zone were repaired simultaneously. • A mathematical simulation was applied to study the temperature change. • The hardened surface showed a high thickness (≥1.3 mm). • The surface hardness could be enhanced by around 36 %. [ABSTRACT FROM AUTHOR]

The paper is proposed that adding OC layer after black matrix process during sensor can improve surface strength of TLCM and surface strength will be better with the increasing thickness of OC layer. The result is suggested that slimming OC0 thickness (<0.8um) significantly sloved optical problem-rainbow issue caused by the wrinkle of OC from ITO sputtering at high temperature (≥230°C); When OC0 thickness exceed over 0.8um, we can adopt lower temperature (<180 °C) ITO sputtering to eliminate rainbow. The paper is also shown to optimize index matching layer to adjust chromaticity and pattern shadow. [ABSTRACT FROM AUTHOR]

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In this work, a novel polymeric fluorescent brightener agent based on 4,4′-diamino-stilbene-2,2′-disulfonic acid-triazine structure has been synthesized by radical polymerization. The structure of 4,4′-diamino-stilbene-2,2′-disulfonic acid -based polymeric fluorescent brightener agent was characterized by Fourier-transform-infrared spectroscopy, HNMR, and gel permeation chromatography. Photo-property was measured and analyzed by the ultraviolet-vis spectra and fluorescence spectra. The performance on paper was evaluated by determining the surface strength and smoothness, the brightness degree, and the post color number value of paper. Results showed that 4,4′-diamino-stilbene-2,2′-disulfonic acid-based polymeric fluorescent brightener agent had a better light stability in water solution than that of 4,4′-diamino-stilbene-2,2′-disulfonic acid-based fluorescent monomer as light stabilizer. Through the surface-sizing experiment and ultraviolet aging experiment, the 4,4′-diamino-stilbene-2,2′-disulfonic acid-based polymeric fluorescent brightener agent not only enhanced the surface strength and smoothness of paper as a surface-sizing agent, but also had a better effect on anti-ultraviolet aging than that of 4,4′-diamino-stilbene-2,2′-disulfonic acid-based fluorescent monomer as a light stabilizer and fluorescent brightener agent. [ABSTRACT FROM AUTHOR]

Penetration test has been a promising technique for characterizing the surface strength of a crusted surface. This paper presents an experimental and numerical investigation of using a flat-ended penetrometer to evaluate the surface strength of mine tailings (MT) treated with biopolymer solutions of different concentrations. The experimental results show that the infiltration depth of biopolymer solution into dry MT decreases with the increase in biopolymer concentration. Biopolymer stabilization effectively increases the surface strength and cracking resistance of MT, and the increase is greater when the biopolymer concentration is higher. To further explore how biopolymer stabilization increases the surface strength and crack resistance of MT, numerical simulations using discrete element method were carried out to study the penetration tests on MT treated with biopolymer solutions of different concentrations. The simulation results show that the inter-particle tensile and shear strengths both increase with higher biopolymer concentration, indicating that more biopolymer induces larger inter-particle bonding and thus increases the surface strength of MT. The simulation results also confirm the delayed formation of cracks on MT after biopolymer stabilization from a microscale perspective, leading to a better understanding of biopolymer stabilization of MT. [ABSTRACT FROM AUTHOR]

In this work, a novel polymeric fluorescent brightener based on coumarin (PFBC) was synthesized, using three-step synthetic route, from 7-amino-4-methylcoumarin, coumarin monomer (FBC), Acrylamide (AM) and methacrylatoethyl trimethyl ammonium chloride (DMC). The structure of PFBC was characterized by FT-IR, 1 HNMR and GPC. PFBC was applied to paper fiber as light stabilizer, fluorescent brightener and surface sizing agent and its performances were evaluated by measuring the UV–vis, fluorescence, thermal stability, the cationic degree, surface strength and smoothness of paper, the brightness degree of paper and the PC value of paper. Results showed that PFBC had better solubility in water than that of FBC, by measuring the optical properties. Through the surface sizing experiment and UV aging experiment, PFBC not only enhanced the surface strength and smoothness of paper as a surface sizing agent, but also had better effect on anti-UV aging than that of FBC as light stabilizer and fluorescent brightener. [ABSTRACT FROM AUTHOR]

A multifunctional fluorescent polymer based on coumarin (MFPC) was synthesized using a four-step synthetic route. To obtain the target compound, 7-amino-4-methylcoumarin, coumarin fluorescent monomer (CFM), and ultraviolet absorber monomer (UVAM) were prepared. By the reaction of CFM, UVAM, trimethyl-2-methacroyloxyethylammonium chloride (DMC), and acrylamide (AM) as a linker, a new multifunctional fluorescent polymer was synthesized. The structure of the MFPC was characterized by Fourier transform infrared (FTIR) and nuclear magnetic resonance (1H-NMR) spectroscopies. The optical properties of MFPC were measured by ultraviolet-visible (UV-vis) and fluorescence spectroscopies, in aqueous solution. The integration effect between MFPC and paper was tested by scanning electron microscopy. The application performance of MFPC on paper was evaluated by measuring the surface strength, smoothness, and whiteness using the printability tester and the UV accelerated aging test. Results indicated that the MFPC had good solubility in water. It also exhibited a positive effect on the light stability and surface strength of paper as a light stabilizer, fluorescent brightener, and surface sizing agent. [ABSTRACT FROM AUTHOR]

For any given environmental conditions the tensile strength of glass is a function of the geometry of the critical flaw and the residual stresses in the vicinity of the flaw. The strength of heat treated glass is conventionally considered to be equal to the sum total of the residual stress and the extrinsic strength of annealed glass. Recent experiments suggest that there is an additional contribution to strength attributable to crack healing. To quantify it, uniaxial and equibiaxial strength tests on both as-received and carefully annealed glass specimens were performed for different edge geometries and edge finishes. The results show that strength recovery attributable to healing is significant, and this strength gain appears to correlate with the quality of the edge finish. Possible explanations of this phenomenon are provided. Independently of healing effects, it was also found that the edge quality has a marginal effect on the mean strength but has a significant positive effect at low fractile values often used in design applications. [ABSTRACT FROM AUTHOR]

Gradient nanotwinned layers (GNTLs) with high hardness of approximately 500 HV and good thermal stability were produced in a Fe–20Mn–3Al–3Si TRIP steel by means of a high strain-rate surface mechanical grinding treatment (SMGT). The effect of the strain-rate on the plasticity-enhancing mechanisms in steels was investigated. It is found that although it primarily exhibits transformation-induced plasticity (TRIP) when cold-rolled, this steel shows twinning-induced plasticity (TWIP) during the SMGT process, illustrating that the steel may undergo a transition from TRIP to TWIP under high-strain-rate deformation. The martensite induced by deformation is thermally unstable and can easily transform back to austenite during annealing. In contrast, the deformation twins (DTs) are thermally much stable, since de-twinning, which plays a key role in the recovery of DTs, is more difficult to occur during thermal annealing. As such, undergoing the same annealing at 600 °C for 1 h, the GNTLs containing a great many of DTs maintain high hardness, whereas the cold-rolled counterpart samples containing deformation-induced martensite softens drastically. [ABSTRACT FROM AUTHOR]

Mine tailings, or mill tailings (MTs), are highly susceptible to wind erosion (dust) and have brought about different environmental and safety concerns. Many efforts have been attempted to stabilize MTs for dust control, but all have drawbacks. The current study investigates the feasibility of using two natural and renewable biopolymers, xanthan gum and guar gum, to stabilize MTs for dust control. Moisture retention and wind tunnel tests were performed to evaluate, respectively, the enhancement of water retention capacity and the improvement of resistance to wind dispersal after MTs were treated with biopolymer solutions of different concentrations. Because the resistance to the formation of dust is closely related to how easy the particles can be detached from the surface, a flat-ended cylindrical penetrometer was manufactured and used to evaluate the surface strength (maximum penetration force) of dry MT specimens treated with biopolymer solutions of different concentrations. Scanning electron microscopy imaging was also performed to investigate the evolvement of the microstructure of MTs after biopolymer treatment. The results indicate that both xanthan gum and guar gum are effective in enhancing the moisture retention capacity, improving the dust resistance, and increasing the surface strength of MTs beyond that of water wetting. This is mainly because the biopolymers form coatings on MT particles and create bonding between them. The results also demonstrate that the flat-ended cylindrical penetrometer is a promising technique for characterizing the dust resistance of MTs. [ABSTRACT FROM AUTHOR]

Acid fracture surface strength plays an important role in acid fracture conductivity. Previous experimental studies have proven mechanical deterioration of carbonate after acid etching. However, such conclusion drawn from cylindrical samples could not be applied into conductivity evaluation as such samples represent the rock mechanical properties of the carbonate mass rather than the fracture surface. As another representative of fracture surface strength, embedment strength has not met an agreement on the evolution pattern during acid etching. So the absence of fracture surface strength measurement data during acid etching causes a challenge to conductivity evaluation and acid fracturing optimization. In an effort to overcome this challenge, scratch test was adopted for the measurement of the fracture surface strength before and after acid etching, as scratch test could acquire the uniaxial compressive strength of asperities on the fracture surface. In an aim to study the influence of mineral composition, acid contact time and acid injection rate, acid etching experiments under different etching conditions were carried out. The scratch test results uncovered the strong heterogeneity on the limestone samples, and strength of limestone fracture surface would experience both rising and declining trend during acid etching process. Dolomite in limestone samples was responsible for the strength increase while Calcite contributed to the decrease of strength according to the X-ray diffraction experimental results. What is more, the rising Dolomite strength and the decreasing Calcite strength affected the average strength of acidized fracture inherently. As acid contact time increased, the firstly strengthened then weakened Dolomite strength and constantly decreasing Calcite strength gave rise to an average surface strength change tendency that rises in the beginning and later declines. The change tendency of surface strength clearly indicated an optimal acid contact time in acid fracturing operation. Calcite strength showed the decreasing trend and Dolomite exhibited both the rising and decreasing trend as injection rate increased, resulting in an indefinite evolution trend of average strength of acid fracture surface. • Scratch test is applied to measure the strength of acid fracture surface. • Acid fracture surface strength is the result of acid reactivity and strength differences between Calcite and Dolomite. • Why optimal acid etching time exists is demonstrated based on change trend of acid fracture surface strength. • Effects of acid etching time on acid fracture surface strength is studied. [ABSTRACT FROM AUTHOR]