Immersion Period Research Articles

Experimental evaluation of fatigue performance of recycled asphalt mixture using refined separation recycled aggregates

In order to improve the utilization of reclaimed asphalt pavement (RAP) in recycled asphalt mixtures (RAMs), RAP was firstly separated into recycled mortar and coarse refined separation recycled aggregates (CRSRAs) with different particle sizes based on a laboratory refined separation method. Meanwhile, the process parameters for RAP separation were optimized by using the orthogonal test method. The related properties of the aggregates before and after refined separation, including residual bitumen binder content, particle agglomeration, angularity, and sphericity, were characterized. The cumulative distribution of sphericity of CRSRAs was fitted with the Weibull function. Asphalt mixtures with 0, 30%, and 50% RAP content were prepared by the Marshall design method. Moreover, the indirect tensile dynamic modulus and fatigue life of these asphalt mixtures after different water immersion periods were evaluated. The results showed that the CRSRAs had a residual binder content less than 1.0% and fewer pseudo particles after refined separation. Furthermore, a bitumen-rich mortar with a particle size less than 2.36 mm and a bitumen content of 10–14% was obtained. Angularity and Weibull fitting results verified that refined separation could homogenize RAP and obtain CRSRAs with a low variability, which helps to prepare better RAMs with high RAP content. RAMs prepared with CRSRAs exhibit superior fatigue performance compared to the traditional RAMs. Their fatigue life was less sensitive to stress changes and fluctuated little with the increasing water immersion time.

Surface Analysis of Magnesium AZ31 Samples Immersed in Various Aqueous Solutions

Rapid degradation in body fluids is known to be the main shortcoming of the AZ31 magnesium alloy that is aimed to be controlled in this study by chemical conversion of its surface in various phosphate and chloride solutions. Deposited layers on the surface of bare alloy plates were subjected to compositional and morphological analyses to assess their performance as barriers to degradation. Also changes in the mass of the samples and pH of the solutions were monitored during 21 day immersion periods. Formations of prismatic, platelike, needlelike crystals of various compositions including calcium phosphates, magnesium phosphates, magnesium chlorides were observed by scanning electron microscopy and their atomic compositions were determined by EDX and quantitative XRD analyses. The results indicate that a layer of ceramic of various thicknesses can stably form on the base alloy by simple adsorption of the particles suspended in the solution or by nucleation and growth of the products of reactions between dissolved ions and the metal ions released from the surface. These deposition layers that are solely induced by the electrochemical potential of the species in the solution offer facile surface modification methods and novel phases to control the degradation of magnesium alloys in aggressive environments such as body fluids or marine environments.

Efficacy of Tannin Extract from Cape Gooseberry Root Physalis peruviana L. as Egg De-Adhesion Agent during Artificial Propagation of African Catfish Clarias gariepinus Burchell

The study assessed the best immersion period and concentrations of the Cape gooseberry root Physalis peruviana that can efficiently remove egg adhesiveness of Clarias gariepinus. One male and one female C. gariepinus brood stock weighing 1.0 kg and 1.3 kg respectively, were used for the experiment. Three different concentrations (0.5%, 1%, and 2%) of tannin extract from Cape gooseberry root were used. Tannic acid (0.75g) diluted in 1 litre of water was used as reference de-adhesion agent, while water was used as control. The fish eggs were rinsed with the solutions at different durations of 0.5, 1 and 2 minutes. Each concentration and rinsing time was recorded in triplicates. Data generated were subjected to Univariate Analysis of Variance Test, and third order Polynomial regression analysis was then used to determine the best concentration and immersion period that neutralizes adhesiveness in eggs of C. gariepinus. Results of the study showed that there were no significant differences (p≤0.05) in the non-adhesive eggs and hatching of eggs immersed in tannin extract from Cape gooseberry root and Tannic acid solution but significantly different from the control. Therefore, this study showed that tannin extract from Cape gooseberry root at 1% concentration and 1 minute immersion period is more efficient for egg adhesion and increase hatching in C. gariepinus.

Mechanical Integrity and In vitro Degradation Behavior of Mg–Zn–Ca Biodegradable Alloy Prepared by Different Casting Technologies

Mg–Zn–Ca alloys have been widely used as biodegradable orthopedic and cardiovascular scaffolds because of their non-cytotoxicity, remarkable biodegradability, good biocompatibility and excellent mechanical properties similar to human bone. However, degradation causes poor corrosion resistance and mechanical properties. In this study, Mg-6%Zn-0.6%Ca alloys were produced using three distinct methodologies: casting, casting via the ultrasonic vibration process (USV), and casting via the mechanical vibration process (MV). Surface characterization, mechanical characteristics and corrosion resistance of the as-cast (untreated) and treated species were studied. The morphology and microstructure showed that the grain size of the as-cast, MV and USV specimens all had average grain sizes of about 191, 93 and 82 µm, respectively. The ultrasonic vibration treated specimen has the greatest degree of grain refinement. Mechanical tests showed that microstructure refinement promotes the mechanical characteristics of Mg alloy, such as compression, ultimate tensile strength as well as elongation. It was observed that the USV-treated sample has exceptional mechanical properties (Compressive strength 360.64 MPa, ultimate tensile strength (UTS) 178.41 MPa and Elongation 3.45%). Corrosion tests revealed that the USV-treated specimen exhibited uniform corrosion and low corrosion rate due to uniform compact fine grains with higher oxide concentration of about 42.82 wt%. The results of electrochemical analyses revealed that the average corrosion rate obtained from Potentiodynamic polarization curves of the as-cast, MV and USV specimens was about 5.3144, 4.5311 and 4.1087 mm/year, respectively and the passive film resistance (Rf) that was obtained from the electrochemical impedance spectroscopy (EIS) model of the USV, MV-treated samples and as-cast sample was 457 Ω, 430 Ω and 204 Ω, respectively. The results of immersion tests revealed that the USV-treated sample lost less weight and exhibits a relatively low degradation rate than the as-cast and MV-treated samples. After two weeks the weight of the as-cast, MV and USV samples decreased by about 18.6%, 18.5%, 16.8%., and the degradation rates were 7.304, 7.097 and 6.78 mm/y, respectively, and then gradually declining over the course of the immersion period.

Corrosion Protection of Galvanised Steel Using Organic Coatings Containing Inhibitive Additives Based on Benzothiazoyl Succinic Acid

It is increasingly apparent that the replacement of highly effective, but environmentally unacceptable chromium (VI)- based inhibitive pigment technologies within protective coatings requires the use of combinations of anti-corrosion additives. There is currently significant interest in using organic inhibitors containing hetero-atoms of nitrogen and/or sulphur in conjunction with conventional Cr(vi)-free inorganic pigments as a means of providing equivalent corrosion protection. One such organic inhibitor is benzothiazoyl succinic acid (BTSA), which is presently commercially available as an in-coating anti-corrosion additive, which can improve the protection capability in existing chromate free formulations. In this work we investigate the ability of BTSA to mitigate corrosion-driven organic coating failure within model coatings applied to hot-dip galvanised steel. In addition, the ability of BTSA to inhibit localised corrosion on bare zinc surfaces when released from a protective coating into corrosive electrolyte within a penetrative defect is also evaluated. A combination of time-lapse imaging and in-situ scanning Kelvin probe (SKP) potentiometry is employed to quantify cathodic delamination rates of model poly-vinyl butyral (PVB) coatings containing varying levels of BTSA additions. It is demonstrated that in-coating BTSA, both added directly to PVB or stored as an exchangeable anion in a layered double hydroxide “smart-release” pigment reduce rates of cathodic disbondment by up to a factor of 20. For both methods of incorporating in-coating BTSA, an increasing loading produces a progressive decrease in delamination rates and a transition from linear to parabolic coating failure kinetics. In addition, it is also demonstrated that BTSA dissolved in the aqueous NaCl (aq) electrolyte applied to a defect can also significantly reduce the rate of cathodic disbondment observed for an unpigmented PVB coating. Highly effective inhibition of localised corrosion of bare HDG surfaces by BTSA additions made to NaCl (aq) electrolyte is demonstrated by a combination on SVET and potentiodynamic studies. Linear polarisation resistance experiments demonstrate an inhibition efficiency of 95% for a 10 mM BTSA addition made to 1% w/v NaCl (aq) at pH 7, while SVET-derived, area averaged current density value are shown to decrease by over an order of magnitude compared with an un-inhibited case over a 6 h immersion period. Using polarisation curves obtained for HDG surfaces in the presence and absence of varying concentrations of dissolved BTSA, a mixed inhibition mechanism is proposed. At intermediate concentrations (1 – 10 mM), BTSA strongly adsorbs on the oxide covered Zn surface via its two carboxylate functional groups, thus hindering electron transfer reactions and providing net cathodic inhibition. At higher concentrations (> 10 mM) an additional reinforcement of any weak points in the adsorbed layer is achieved by virtue of the formation of an insoluble salt formed by reaction with Zn(ii) cations, producing a positive shift in free corrosion potential. In-coating BTSA appears to stifle cathodic disbondment by adsorbing strongly on the intact organic-coated metal, which in turn hinders underfilm oxygen reduction and the dissolution of the amphoteric zinc(hydr)oxide layer at the metal-polymer interface.

Microbiological, physicomechanical, and surface evaluation of an experimental self-curing acrylic resin containing halloysite nanotubes doped with chlorhexidine

ObjectiveThe objective was to synthesize halloysite nanotubes loaded with chlorhexidine (HNT/CHX) and evaluate the antimicrobial activity, microhardness, color change, and surface characteristics of an experimental self-curing acrylic resin containing varying concentrations of the synthesized nanomaterial. MethodsThe characterization of HNT/CHX was carried out by calculating incorporation efficiency, morphological and compositional, chemical and thermal evaluations. SAR disks were made containing 0 %, 3 %, 5 %, and 10 % of HNT/CHX. Specimens (n = 3) were immersed in distilled water and spectral measurements were carried out using UV/Vis spectroscopy to evaluate the release of CHX for up to 50 days. The antimicrobial activity of the composite against Candida albicans and Streptococcus mutans was evaluated by disk-diffusion test. Microhardness, color analyses (ΔE), and surface roughness (Ra) (n = 9) were performed before and after 30 days of immersion. Data were analyzed using ANOVA/Bonferroni. {Results.} The incorporation efficiency of CHX into HNT was of 8.15 %. All test groups showed controlled and cumulative CHX release up to 30 or 50 days. Significant antimicrobial activity was verified against both microorganisms (p < 0.001). After the 30-day immersion period, the 10 % HNT/CHX group showed a significant increase in hardness (p < 0.05) and a progressive color change (p < 0.001). At T0, the 5 % and 10 % groups exhibited Ra values similar to the control group (p > 0.05), while at T30, all groups showed similar roughness values (p > 0.05). {Significance.}The modification of a SAR with HNT/CHX provides antimicrobial effect and controlled release of CHX, however, the immediate surface roughness in the 3 % group was compromised when compared to the control group.

Investigation of the effects of immersion period of simulated body fluid on the morphology and structural properties of Fe/Ni co-doped chlorapatites

In this study, chlorapatite (ClAp) samples co-doped with Fe and Ni at different amounts were synthesized using a wet chemical method. The as-produced samples were immersed in simulated body fluid (SBF) for 14 and 28 days. The samples were characterized before and after soaking in SBF, and their morphologies and structural properties were compared to each other. It was observed that the immersion period in SBF and the amount of Fe and Ni affected the morphology and structural properties of the ClAp samples.

Enhancing corrosion resistance and toughness of solvent-free epoxy coatings with low-viscosity fluorine-containing hyperbranched polyether

In this study, a low-viscosity epoxy-terminated fluorine-containing hyperbranched polyether (FHBPE) was synthesized and incorporated in a solvent-free epoxy coating formulation to enhance coating toughness and corrosion resistance while minimizing the impact on coating viscosity. FHBPE was synthesized by a solvent-free one-pot method with hexafluorobisphenol A (A2 monomer) and trimethylolpropane triglycidyl ether (B3 monomer). Subsequently, FHBPE, E51 epoxy resin, and an alicyclic amine curing agent were blended to create the solvent-free epoxy coating, which was applied onto a steel substrate by a scraping coating method. This research demonstrates that addition of FHBPE did not show adverse effect on coating viscosity; instead, it reduced the viscosity at around 6 wt% loading. The epoxy-terminated FHBPE increased the cross-linking density of neat E51 coating by up to 20.7 %. Furthermore, the introduction of flexible segments enhanced the toughness, leading to a one-grade increase in the coating flexibility from 1 to 0.5 mm. Furthermore, FHBPE significantly improved the corrosion resistance of the coatings, attributed to increased cross-linking density and hydrophobic properties of the coating. Among FHBPE-modified coatings, the coating with 6 wt% loading demonstrated superior overall performance. Over a 60-day immersion period, its electrochemical impedance value remained stable, while the neat E51 coating experienced a two-orders-of-magnitude decrease. Furthermore, the 6 wt% FHBPE-modified coating passed the 750-h salt spray test without obvious rust, outperforming the neat E51 coating (200 h). This study presents a feasible and promising strategy for the formulation design and mass production of solvent-free epoxy coatings.

Evaluation of Corrosion Behaviour by Gravimetric Method

The study aims to evaluate the corrosion behaviour of two steels: BL245 and S235JR, produced at Liberty Steel Galati. BL245 is an alloy used in the oil and gas industry to manufacture pipes for pipeline transportation systems. S235JR is used to make hot finished hollow sections for construction. Gasoline, diesel and a 3.5% sodium chloride solution were chosen as corrosion environments for this study, considering the field of use of the two alloys (oil and construction). Corrosion assessment was analysed using the gravimetric method, which is based on weighing the samples before and after they were immersed for 7, 14, and 35 days in the above-mentioned corrosion environments. Based on the initial weighing and those recorded after the immersion periods, the mass variation of the samples was determined, and the corrosion rate and penetration index were calculated.

Color stability of nano resin-modified glass Ionomer restorative cement after acidic and basic medications challenge

Background: Color stability of glass ionomers (GIs) could be affected by many factors such as pH and consumption of liquid medications like antibiotics. Most common antibiotics used during childhood are amoxicillin suspension (AM.S) and azithromycin suspension (AZ.S) which have acidic and basic pH respectively. Aim: to evaluate and compare the effect of AM.S and AZ.S on color stability of nano resin-modified GI. Methods: Thirty disc of nano resin-modified glass ionomer (2mm height x 4mm diameter) were divided into three groups (n=10 for each) and independently exposed to AM.S, AZ.S, and artificial saliva (A.S.). Color stability was evaluated in triplicate by VITA Easyshade® before and after three immersion protocols, repeated over a three-week duration with two-days intervals. In each protocol, samples were exposed for two minutes, three times daily for AM.S, once daily for AZ.S, and A.S. full day. GI discs rinsed off after each immersion and kept in artificial saliva until next immersion period. Results: One way ANOVA test and Post-hoc analysis of the changes in color space compartments of nano-resin modified GI samples demonstrated just a significant change (p˂0.05) in yellow-blue axis (Δb*) value after immersion in AM.S in comparison with A.S. Total Color change values (ΔE) of nano resin-modified glass ionomer samples also illustrated a significant effect (p˂0.05) between AM.S and A.S. only. The highest (ΔE) value was recorded for samples immersed in AM.S (ΔE =12.5) followed by AZ.S (ΔE=6.5) while the lowest was recorded for A.S. (ΔE=1.1). Conclusion: AM.S (the acidic medication) exhibited a higher staining effect to nano-resin modified GI samples when compared with AZ.S (the basic medication). Several factors such as low pH, more exposure time and coloring material of the immersion media added critical roles in coloring instability.

Role of Plant Growth Regulators on Multiplication of Stevia rebaudiana Inside Manufactured Temporary Immersion Bioreactor and Induction of Callus from Explant

The experiment was conducted at Plant Tissue Culture Laboratory - Department of Horticulture and landscape gardening, from October 2021 to January 2023. micropropagation experiments were conducted using five levels of Kinetin 0.0, 1.0, 2.0, 3.0, and 4.0 mg L. Callogenesis experiments were performed using four levels of Naphthalenacetic Acid 0.0, 1.0, 2.0, and 3.0 mg L. A temporary immersion bioreactor was used with a 10-minute immersion period every 4 hours, and two levels of Kinetin and two levels of benzyl adenine were added to the Murashige and Skoog medium as a comparative treatment. The results showed that the concentration of 1.0 mg L had a significant effect on the number of shoot and leaves, and the comparative treatment showed a significant effect on shoots height. The results of multiplication in the manufactured bioreactor showed a significant effect on shoots height, reaching 4.8 cm, and the concentration of 1.0 mg L benzyl adenine showed a significant effect on the number of shoots, with 3.2 shoot per plant, and the number of leaves for the same treatment was 17.1 leaves per shoot.

Enhanced corrosion resistance properties of 15Al-85Zn coating by post-treatment with sodium hexa-meta phosphate in saline solution

Different amounts of sodium hexametaphosphate (SHMP: Na6[(PO3)6]) has been used to fill the defects and pores of arc thermal sprayed 15Al-85Zn coating. 73.39% porosity is reduced by 0.1 M SHMP post-treated coating due to formation of hydrogen zinc phosphate hydrate (HZP: HZn4(PO4)3H2O). The corrosion resistance of post-treated coating is increased in 3.5 wt% NaCl solution with immersion periods attributed to the transformation of HZP into zinc phosphate (Zn3(PO4)2) as well as active Zn react with Cl- and form simonkolleite (Zn5(OH)8Cl2·H2O). Simonkolleite and zinc phosphate are sparingly soluble, therefore, post-treated coating provides two folds’ protection by HZP and corrosion products.

In vitro long-term antibacterial performance and mechanism of Zn-doped micro-arc oxidation coatings

Micro-arc oxidation (MAO) coatings containing 2.86 wt%, 5.83 wt% and 8.81 wt% Zn (Zn-2.86 wt%, Zn-5.83 wt% and Zn-8.81 wt%) were separately fabricated on Ti6Al4V alloys using EDTA-ZnNa2 electrolytes. In vitro antibacterial examination exhibits that the antibacterial rates of Zn-2.86 wt%, Zn-5.83 wt% and Zn-8.81 wt% against Staphylococcus aureus (S. aureus) are 76.0 %, 100.0 % and 99.2 %, respectively. Reactive oxygen species (ROS) level of MAO samples is significantly higher than that of the untreated Ti6Al4V. Zn-containing coatings especially Zn-5.83 wt% induces the strongest oxidative stress on S. aureus due to relatively high released Zn2+ concentration. Moreover, qPCR analysis shows that MAO samples inhibit the icaADBC transcription and result in the down-regulation of PIA production, thereby mitigating biofilm formation. After immersion in simulated body fluid (SBF) for 3, 8 and 14 d, the antibacterial rate of Zn-5.83 wt% is 84.7 %, 63.2 % and 12.5 % respectively, and ROS level of MAO samples is also significantly higher than that of the untreated Ti6Al4V even after 14 d of immersion, suggesting that the antibacterial performance of MAO samples can last a relatively long immersion period and exhibit large application potential in orthopedic clinic.

The combined effect of hydroxyapatite and zirconia coatings on magnesium-based-implant to improve corrosion resistance and induce antibacterial activity

In this research, zirconium has been used in two methods of, single-step and double-step, to improve the anticorrosion properties of Hydroxyapatite (HA) coating. The corrosion behavior of the samples and the performance of the coatings in the physiological environment were investigated by EIS and DC polarization tests in 3.5 wt% sodium chloride and SBF solution, respectively. The results of the electrochemical assays showed that the best resistance against corrosion and biocorrosion is obtained for the sample prepared by the double-step method (HAopt/Zropt sample). FE-SEM and XRD were used to examine the morphology and composition of the coatings that confirmed the formation of HA crystals and the amorphous zirconium layer. According to the antibacterial results, HA/zirconia coating provided a remarkable antibacterial performance (RP =99.9%) against Staphylococcus aureus gram-positive and Escherichia coli gram-negative bacteria. Also, HAopt/Zropt sample provided the highest corrosion resistance of about 9000 ohm.cm2 in NaCl, and |Z|0.01 Hz= 3.5 × 105 ohm.cm2 in SBF solution in a prolonged immersion period.

Electrochemical Corrosion Behavior in Simulated Body Fluid of a Metastable β‐Type Ti29Nb13Ta4.6Zr Biomedical Alloy with Improved Mechanical Properties

Herein, the mechanical properties and corrosion behavior in simulated body fluid of the β‐type Ti29Nb13Ta4.6Zr alloy (TNTZ) are investigated and compared to Ti6Al4V alloy. The samples are obtained from the solution‐treated (ST) and water‐quenched TNTZ bars. Following quenching, the bars are cold rolled aged (CRA) at 673 K for 20 min in order to reach a desired combination of high yield strength and low elastic modulus. The corrosion tests are conducted using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) during a long period of immersion in physiological Ringer's solution (up to 144 h), and the mechanical behaviors are assessed through uniaxial tensile tests. The results show that both TNTZ ST and CRA conditions have lower Young's moduli than Ti6Al4V. However, with CRA treatment, the alloy is significantly strengthened due to a homogeneous precipitation of nanometer‐sized α‐phase with lenticular morphology in the β‐matrix. Potentiodynamic polarization and EIS results reveal that both TNTZ CRA and Ti6Al4V passivate under testing conditions, and the passive current density is very low, providing corrosion resistance in the potential range studied. The EIS results also reveal that the passive film formed on the surface of both materials is highly corrosion resistant.

Study on the mechanical properties of embankment soil under long-term immersion conditions

During flood season, embankments are often submerged in high water levels for extended periods, leading to deterioration in their soil mechanics performance and increasing the risk of slope instability and other hazards. In order to investigate the changes in mechanical properties of embankment slopes during long-term water immersion, direct shear tests were conducted. Scanning electron microscopy, chemical composition analysis, and laser particle size analysis were conducted on samples taken at different immersion periods. Clay samples were taken from the embankments at Jiangxinzhou in Nanjing, Jiangsu Province, China. Results showed the shear strength of the soil gradually decreases with the increase of immersion time, while the cohesive force and internal friction angle gradually decrease as well. This suggests that immersion has a softening effect on the shear strength of the soil. As the immersion time increases, the colloidal particles (soluble salt) rapidly dissolves, the microstructure of the soil is destroyed, and sticky particles increases, resulting in a change in the shear strength of the soil. The research results provide a basis for flood control and prevention of embankments immersed in high water levels for long periods during the flood season.

Synthesis and Characterization of Bioactive Glass and Zinc Oxide Nanoparticles with Enamel Remineralization and Antimicrobial Capabilities.

We investigated the effect of bioactive glass and zinc oxide nanoparticles on enamel remineralization, as well as their antimicrobial effect on cariogenic microbes. This is the first study that investigated the properties of bioactive glass and zinc oxide nanoparticles with mixed materials. Fluoride gel (F), bioactive glass microparticles (µB), bioactive glass nanoparticles (nB), zinc oxide nanoparticles (Z), and a mixed suspension of nB and Z (nBZ) were prepared and characterized by scanning and transmission electron microscopy, zeta potential measurement, X-ray diffraction, and acid buffering capacity testing. Further, we performed a remineralization cycle test of 28 days, and nanoindentation testing was carried out during the immersion period, and then the enamel surfaces were examined using scanning electron microscopy. Additionally, the antimicrobial effects of the sample suspensions were evaluated by measuring their minimum microbicidal concentrations against various cariogenic microbes. Our results revealed that nB had a near-circular shape with an amorphous structure and a considerably large specific surface area due to nanoparticulation. Additionally, nB possessed a rapid acid buffering capacity that was comparable to that of μB. In the remineralization test, faster recovery of mechanical properties was observed on the enamel surface immersed in samples containing bioactive glass nanoparticles (nB and nBZ). After remineralization, demineralized enamel immersed in any of the samples showed a rough and porous surface structure covered with mineralized structures. Furthermore, nBZ exhibited a broad antimicrobial spectrum. These results demonstrated that bioactive glass and zinc oxide nanoparticles have superior demineralization-suppressing and remineralization-promoting effects.

Tear Strength Evaluation of Maxillofacial Silicone After Disinfection with Oregano Oil Solution

The main objective of this study was to evaluate the tear strength property after disinfection with plant-based disinfection solution after different immersion periods. Materials and methods: Forty specimens of VST-30 maxillofacial silicone were prepared then divided into four main groups (n= 10), a control group that was not subjected to disinfection and three experimental groups subjected to disinfection in different immersion time (1 day, 1 month, and 6 months). The experimented groups were immersed in Oregano oil solution. The tear strength test was performed by the use of Universal Testing Machine. Statistical analyzes of the data was perfor med via One-way ANOVA and Tukey HSD Post-hoc test to determine the significant differences between experimen tal and control groups at a level of significance (p ≤ 0.05 ). Results: The tear strength test showed a non-significant difference between the control group and the experimental groups. Also, there was no significant differences among the three experimental gr oups. Conclusion: tear str ength of VST-30 silicone elastomer was not affected after im mersion in 0.4% Oregano solution.

Progressive failure characteristics and water-induced deterioration mechanism of fissured sandstone under water–rock interaction

Stability of engineered rock mass can be significantly affected by the combined action of fissures and water. In this study, uniaxial compression tests of fissured sandstone under natural state and water-chemical environments were conducted, accompanied by acoustic emission and digital image correlation to monitor the whole failure process. The results indicate that the strength and elastic modulus of fissured sandstone in the saturated state were lower than those in the natural state. The inside structural changing of dried specimen after water–chemical environments immersion had a weak influence on the strength and elastic modulus, but the peak strain and yield deformation would significantly increase. Characteristic stress determination methods were identified applicable to fissured sandstones under water–rock interactions. The σci/σf (the ratio of crack initiation stress to peak strength) could be largely degraded by the presence of water, while the impact on σcd/σf (the ratio of crack damage stress to peak strength) was weak. The structural changing could also significantly reduce σci/σf. However, only the σcd/σf ratio in the acid water environment exhibited the obvious reduction. The presence of water could also influence the crack initiation and failure mode of fissured sandstone. After a short period of immersion (45 d), the strength and elastic modulus degradation of fissured sandstone was mainly caused by the water–rock physical reaction, while the change in the peak strain was jointly affected by the water–rock chemical and water–rock mechanical reactions. The σci/σf ratio was affected by the water–rock chemical and water–rock mechanical reactions, while the σcd/σf ratio was affected only by the water–rock chemical reaction. Moreover, the water–rock mechanical reaction significantly changed the initiation mode of fissured sandstone. The water-induced deterioration mechanism of fissured sandstone was lastly revealed by these results, which could provide an important reference for evaluating the stability of water-rich engineered rock mass.

Recycled eggshell waste in zinc-rich epoxy coating for corrosion protection of mild steel in a controlled elevated temperature saline environment

Eggshell wastes have attracted interest in the fabrication of anticorrosion coatings due to chemical compositions (high calcite content) and widespread availability. This study presents the use of chemically and thermally treated eggshell nanoparticles as fillers in a zinc-rich epoxy matrix in corrosion protection of mild steel in sodium chloride solution at an elevated temperature. Three samples of zinc-rich coatings containing “as ball-milled” eggshell, chemically and thermally treated eggshell nanoparticles were fabricated to form zinc-rich eggshell nanoparticles epoxy (ZENE) coatings. The structural characterizations indicated that chemical and thermal treatment removed the protein materials from eggshell nanoparticles, leading to a 10-fold increase in electrical conductivities and prolonged the cathodic sacrificial behaviour of the ZENE coatings throughout the immersion period. The electrochemical impedance study of these coatings after immersion in an elevated-temperature corrosive environment showed that chemically-treated eggshells in comparison with thermally-treated ones could effectively remove protein materials from the eggshell nanoparticles. These nanoparticles as fillers in the zinc-epoxy matrix significantly enhanced the anticorrosion performance by improving the cathodic as well as barrier protection properties of the coating. A proposed corrosion protection mechanism of the ZENE coatings in 3.5 wt% NaCl solution revealed that the improved electrical conductivity of the treated eggshell nanoparticles enhanced the galvanic contact at the interstitial spaces between the zinc particles while prolonging the zinc cathodic sacrificial behaviour. Thus, this study demonstrated the sustainable use of eggshell wastes in enhancing the anticorrosion properties of zinc-rich epoxy coatings.