Small Amount Of Water Research Articles

Experience of using the NALCO 1392 scale inhibitor in the circulating water supply system of the Novovoronezh NPP

Power facilities use large amounts of water to cool steam in the steam turbine condensers, and lubricating oils, gas and air in turbine sets. The key requirement for the quality of cooling water is to ensure normal vacuum in condensers. Cooling water must not form mineral and biological deposits and corrosion products in the system. Deposits of mineral salts in the condenser tube system, as well as in auxiliary cooling systems, lead to deterioration in heat exchange and a major decrease in the cost effectiveness of the power equipment operation, and require the heat-exchange equipment to be periodically cleaned. The source water used for cooling is normally taken from nearby water bodies (large rivers or lakes). Circulating water supply systems are used most commonly: these systems use repeatedly the same water inventory for cooling, and require only small amounts of water added to make up for evaporation losses. Coolers, in this case, are cooling towers, spray pools and evaporation ponds. The water chemistry should ensure the operation of equipment without any damage to its components or the loss of efficiency caused by the corrosion of the internal surfaces as well as without scale and sludge formation. It is exactly when using circulating water supply that a stabilizing treatment program is the most practicable way to ensure a cost-effective and environmentally friendly mode of operation. To inhibit scaling processes on the heat-exchange surfaces of the turbine condenser tubes at the Novovoronezh NPP’s unit 5, the cooling water was treated with the NALCO 1392 inhibitor. The results of the NALCO 1392 inhibitor pilot tests in the circulating water supply system (with a cooling pool) are presented.

Formation of type 3 resistant starch from mechanical activation-damaged high-amylose maize starch by a high-solid method

This study focused on constructing a high-solid reaction system to prepare type 3 resistant starch (RS3) with high-amylose maize starch as raw material by mechanical activation (MA) pretreatment combined with thermal and freeze–thaw treatments. MA pretreatment effectively destroyed the crystal structure and molecular structure of native starch. MA damaged starch with a certain viscosity could form dough with a small amount of water to construct a starch continuous phase system. RS content increased with the damage levels of starch as the formation of double helix structure, attributed to that the molecules of MA damaged starch could be easy to move and form recrystallization structure. Thermal and freeze–thaw treatments contributed to strong interaction of starch–water and the re-formation of internal crystal structure of MA damaged starch to form RS3. This study provides insight into the development of a highly effective approach for large scale production of resistant starch.

Water-induced release of recalcitrant polycyclic aromatic hydrocarbons from soil organic matter during microwave-assisted solvent extraction

Polycyclic aromatic hydrocarbons (PAHs) in soil can be recalcitrant to solvent extraction after aging. We showed in this study that mixing a small amount of water in the extracting solvent during microwave-assisted extraction (MAE) can release recalcitrant PAHs, resulting in significant improvement in the analyzed concentrations. The improvement factor (F) for the total of 16 priority PAHs (∑PAH16) listed by the United States Environmental Protection Agency was 1.44–1.55 for field soils. By comparing the F values for different soil organic components, we demonstrated that the recalcitrant PAHs were primarily associated with biochar, humic acid (HA), and humin (HM), with the F values for ∑PAH16 of 1.94, 6.62, and 4.59, respectively. The results showed that the recalcitrant PAHs comprised a sequestered fraction and a desorption-limited fraction. NMR spectra showed that water worked alone at elevated temperature to promote hydrolysis of biochar and destroy the macromolecular structure, thus causing the release of the otherwise sequestered PAHs during MAE. The substantial reduction in F values for HA and HM after demineralization indicated sequestration of PAHs in organic-mineral complexes, which can be destroyed by hot water treatment. The release of the sequestered fraction was nonselective and independent of compound hydrophobicity. In comparison, the release of the desorption-limited fraction was positively affected by the hydrophobicity of PAHs and was facilitated by the presence of water in the extracting solvent. The results of this study provide important insights into the sequestration and release of recalcitrant PAHs in soil.

Self-Sensitized LiErF4: 0.5%Tm3+ upconversion Nanoprobe for Trace Water Sensing

IntroductionWater is not only the most precious resource on earth, but also the most important component of the organism, which is vital to life. However, sometimes even a very small amount of water is dangerous. When water is present in fuels, organic solvents, it can sometimes cause serious consequences. Therefore, moisture monitoring and measurement play a very important role in basic research, industrial synthesis and etc.At present, the standard method for detecting moisture is the Karl Fischer method[1], which is complicated and time-consuming, therefore is not suitable for rapid determination and repeated measurement of moisture. The optical moisture sensor has the advantages of simple operation, fast response, etc. The rare earth-doped upconversion nanoprobes have the advantages of stable chemical properties, large anti-Stokes shift, and stable optical properties, which has attracted great attention in the sensor field[2-3].Here, a water detection probe based on LiErF4: 0.5% Tm3+@LiYF4 under 808nm excitation was constructed to detect the trace water in organic solvents with detection limit of 30 ppm in acetonitrile, 50 ppm in DMSO and 58 ppm in DMF under excitation of 808 nm.MethodTmCl3·6H2O (0.0025mmol) and ErCl3·6H2O (0.4975 mmol) were added to 6 mL oleic acid and 15 mL 1-octadecene. The solution was heated to 150℃ and stirred for 30 minutes before cooled down to 30℃. NH4F (2mmol ) and LiOH (1.25 mmol) dispersed in 10 mL methanol were added to the mixture, then heated to 80℃ lasted for 30 min to remove the methanol. The solution was then heated to 300℃ and keep for 90 min before cool down to room temperature. Finally, the LiErF4: 0.5% Tm3+@LiYF4 nanoparticles were washed by acetone and anhydrous ethanol and dispersed in 4ml cyclohexane.YCl3·6H2O (0.25 mmol) was added to a mixture of 6 mL OA and 15 mL ODE and stirred continuously for 30 min. The solution was heated to 150℃ maintained for 30min, then cooled down to 30℃, 5mL methanol containing NH4F (1mmol) and LiOH (0.625mmol) was added and then heated to 80℃ for 30min to remove the methanol, 2ml cyclohexane containing the core LiErF4:0.5%Tm nanoparticles was added and then heated to 90℃ lasted for 30min to remove the cyclohexane. Finally, the mixture was heated to 305℃ lasted for 90min. The LiErF4: 0.5% Tm3+@LiYF4 nanoparticles were obtained and washed with acetone and ethanol respectively, then dispersed in 4ml cyclohexane.Nitrogen protection and continuous stirring are required throughout the experiment.The oleic acid coated nanoparticles were dispersed in DMF/acetonitrile/DMSO (10mL) and then ultrasonicated for 10 min to remove the oleic acid. The ligand-free nanoparticles were collected by centrifugation at 13000 rpm for 15 min, washed with DMF three times, and redispersed in DMF/acetonitrile/DMSO.Results and ConclusionsBecause of the high concentration of Er3+ ions in the nanoprobe, the interaction among Er3+ ions is very strong and easy to be affected by the environment. When there is water in the solution, the nanoprobe will transfer energy to the water molecules, leading to the upconversion emission quenching. The response sensing of water molecules was realized by detecting the red emission of nanoprobe with the change of water content in DMF.The results showed that the red emission intensity of the nanoprobe was weakened obviously with the increase of water content in the solution and there is a good linear relationship between the logarithm of the change in emission intensity (ln(F/F0)) and water content (vol%) . The limit of detection in DMF , acetonitrile and DMSO can be down to 58ppm, 50ppm and 30ppm, respectively. The results are of great significance for the development of reusable water test strips and highly sensitive detection instruments.

Hydrothermal Synthesis, Crystal Structure, and Spectroscopic Properties of Pure and Eu3+-Doped NaY[SO4]2 ∙ H2O and Its Anhydrate NaY[SO4

The water-soluble colorless compound NaY[SO4]2 ∙ H2O was synthesized with wet methods in a Teflon autoclave by adding a mixture of Na2[SO4] and Y2[SO4]3 ∙ 8 H2O to a small amount of water and heating it up to 190 °C. By slow cooling, single crystals could be obtained and the trigonal crystal structure of NaY[SO4]2 ∙ H2O was refined based on X-ray diffraction data in space group P3221 (a = 682.24(5) pm, c = 1270.65(9) pm, Z = 3). After its thermal decomposition starting at 180 °C, the anhydrate NaY[SO4]2 can be obtained with a monoclinic crystal structure refined from powder X-ray diffraction data in space group P21/m (a = 467.697(5) pm, b = 686.380(6) pm, c = 956.597(9) pm, β = 96.8079(5), Z = 2). Both compounds display unique Y3+-cation sites with eightfold oxygen coordination (d(Y–Os = 220–277 pm)) from tetrahedral [SO4]2− anions (d(S–O = 141–151 pm)) and a ninth oxygen ligand from an H2O molecule (d(Y–Ow = 238 pm) in the hydrate case. In both compounds, the Na+ cations are atoms (d(Na–Os = 224–290 pm) from six independent [SO4]2− tetrahedra each. Thermogravimetry and temperature-dependent PXRD experiments were performed as well as IR and Raman spectroscopic studies. Eu3+-doped samples were investigated for their photoluminescence properties in both cases. The quantum yield of the red luminescence for the anhydrate NaY[SO4]2:Eu3+ was found to be almost 20 times higher than the one of the hydrate NaY[SO4]2 ∙ H2O:Eu3+. The anhydrate NaY[SO4]2:Eu3+ exhibits a decay time of about τ1/e = 2.3 µm almost independent of the temperature between 100 and 500 K, while the CIE1931 color coordinates at x = 0.65 and y = 0.35 are very temperature-consistent too. Due to these findings, the anhydrate is suitable as a red emitter in lighting for emissive displays.

The control mechanisms of lysine sulfate dust deflagration flame propagation based on flame microstructures and time scale analysis

A series of experiments of the deflagration flame propagation of Lysine sulfate (LS) powder were conducted in a vertical tube with different moisture contents, particle sizes and mass concentrations. The thermal flame model was applied to investigate the dust flame micro-structures combined with the ion probes and the fine thermocouples. The time scales of the dust combustion sub-processes were calculated to reveal the control mechanisms during flame propagation. Results showed that a small amount of water significantly reduced the flame thickness and the heat transfer time, like the SEEP effects (Suppressant Enhanced Explosion Parameter). The practicability of applying the thermal flame model for dust flame was proved. As the mass concentration increased, the effect of the pyrolysis enhanced initially and then decreased during the gas phase combustion process, and the effect of heat transfer weakened during the pyrolysis process.

Sintering of degradable bone substitutes at room temperature

The possibility of preparing bone substitutes in clinic is demonstrated in this study. With the addition of a small amount of water, the relative density of the calcium sulfate specimen prepared at room temperature became higher than 92%. This value is close to the density of the specimen prepared through conventional sintering at 1100 °C for 1 h. The biaxial strength of the specimen disc can reach 120 MPa. Densification is assisted by the hydration of calcium sulfate hemihydrate to dihydrate wherein coarse hemihydrate particles transformed to fine dihydrate dendrites. Strength is conferred by the entanglement of dendrites and microstructure refinement. The densified calcium sulfate disc remains degradable; its degradation rate in a phosphate buffer saline solution is ~1.6 wt%/day, and the rate remains steady for 28 days.

The Brief Case: Salmonella enterica Serovar Typhi in a Central American Refugee.

An unvaccinated teenage male with no known past medical history presented to the emergency department (ED) with complaints of headache, back and neck pain, and fever with chills for 2 days before presentation. In addition, he reported constipation (bowel movement only every 3 days), rhinorrhea, and congestion. He denied abdominal pain, shortness of breath, or photophobia. Social history revealed that he had traveled alone from Central America to the United States and had spent ∼7 days in the Sonoran Desert of Mexico and southern Arizona with only crackers, apples, and small amounts of water (source unknown). The patient had been in United States Border Patrol custody for ∼2 weeks before presenting to the ED.

Selecting Suitable MODFLOW Packages to Model Pond–Groundwater Relations Using a Regional Model

In large-scale regional models, used for the management of underground resources, it is quite common to find that relationships between the regional aquifer and small wetlands are not included. These models do not consider this connection because of the small amount of water involved, but they should consider the potential for significant ecological impacts if the groundwater resources in the ecosystems associated with these wetlands are mismanaged. The main objective of this work is to investigate the possibilities offered by MODFLOW LGR-V2 to represent (at small scale) the Santa Olalla pond, located in the Doñana Natural Park (South of Spain), and its relationship with the Almonte-Marismas regional aquifer. As a secondary objective, we propose to investigate the advantages and disadvantages that DRAIN, RIVER and LAKE MODFLOW packages offer within the MODFLOW LGR-V2 discretizations. The drain boundary condition with a coarse discretization implemented through ModelMuse allows the most adequate performance of the groundwater levels in the environment of the pond. However, when using lake boundary condition, the use of the MODFLOW LGR-V2 version is particularly useful. The present work also gives some guidelines to employ these packages with the MODFLOW graphical user’s interface, ModelMuse 4.2.

Spectroelectrochemical Behaviour of 1,4‐Dimethoxypillar[5]arene (P5A) and its Monomer in Different Organic Solvents

AbstractThe spectroelectrochemical response of the macrocyclic compound 1,4‐dimethoxypillar[5]arene (P5A) and its monomer 1,4‐dimethoxybenzene was investigated using cyclic voltammetry combined with UV‐Vis spectroscopy. The influence of three different aprotic solvents, acetonitrile, dichloromethane, and dichloroethane, as well as supporting electrolyte, on the anodic behaviour of P5A were studied and discussed. The results indicate that the donor‐acceptor Lewis‐type interactions between tested compounds and the solvent molecules affect the oxidation processes and thus the formal potentials (Ef). In all solvents we see subsequent oxidation of P5A to P5A5+ followed at higher potential by an irreversible oxidation to the corresponding quinone. The results also show that small amounts of water can significantly influence the redox behaviour of the P5A.

Role of 1-methylimidazole in regulating the CO2 capture performance of triethylenetetramine-based biphasic solvents

Biphasic solvents are promising candidates for CO2 capture for low regeneration energy consumption. In this study, a novel phase splitter 1-methylimidazole (1-MI) was proposed for triethylenetetramine (TETA) aqueous solvent. 1-MI was proved to act as a phase splitter to induce the phase separation and as an absorption promoter to enhance the absorption rate. By tuning the concentrations of TETA and 1-MI, good phase separation performance was obtained in TETA-1-MI biphasic solvent, achieving a CO2-rich phase loading of 5.41 mol/L. 13C NMR revealed that the upper layer was the CO2-lean phase, containing 1-MI and a small amount of water, while the lower layer was the CO2-rich phase and mainly comprised of TETAH+ and TETA-carbamate. The kinetics results based on the double-film theory indicated that the CO2 absorption rate was mainly controlled by the gas film mass transfer resistance at lower CO2 loading and then by liquid film mass transfer resistance when CO2 loading was higher than 1 mol/L. Owing to the good phase separation behavior triggered by 1-MI, the regeneration heat of TETA-1-MI was 2.26 GJ/t CO2, which was comparable to that of the second-generation solvents, and 43.5 % lower than that of 5 M monoethanolamine (MEA). The present findings indicated that TETA-1-MI had a large loading capacity, high absorption rate, and low energy consumption, which can serve as a novel candidate for CO2 capture.

Durability and Fire-Hazardous-Risk Evaluation of Unique Phase Separation Solvent Using High-Boiling Amine and Ether

Durability and fire hazard risk evaluation were conducted to determine the process feasibility on the unique phase separation solvent with low regeneration temperature (90 °C), consisting of amine, ether, and small amount of water. The results we obtained are as follows; I) The amine degradation rate of the phase separation solvent would be less than 1/10 of that of monoethanolamine (MEA), which was contributed by its high oxidative resistant nature and low regeneration temperature. II) The gas composition formed in the absorber was completely out of combustible range and almost no accumulations of explosive compounds such as peroxides were observed when in contact with 6 % oxygen containing gas (dry base). Therefore, we believe that the phase separation solvent is applicable to the treatment of exhaust gas from coal-fired thermal power plants.

Maximizing Oxygen Evolution Performance on a Transparent NiFeOx/Ta3N5 Photoelectrode Fabricated on an Insulator.

A transparent Ta3N5 photoanode is a promising candidate for the front-side photoelectrode in a photoelectrochemical (PEC) cell with tandem configuration (tandem cell), which can potentially provide high solar-to-hydrogen (STH) energy conversion efficiency. This study focuses in particular on the semiconductor properties and interfacial design of transparent Ta3N5 photoanodes fabricated on insulating quartz substrates (Ta3N5/SiO2), typically the geometric area of 1 × 1 cm2 in contact with indium on its edge. This material utilizes the self-conductivity of Ta3N5 to make the PEC system operational, and the electrode would strongly reflect the intrinsic nature of Ta3N5 without a back contact that is commonly introduced. First, PEC measurements using acetonitrile (ACN)/H2O mixed solution were made to elucidate the intrinsic photoresponse in the presence of tris(2,2'-bipyridine)ruthenium(II) bis(hexafluorophosphate) (Ru(bpy)3(PF6)2) without water contact which avoids a multielectron-transfer oxygen evolution reaction (OER) and photoinduced self-oxidation. The potential difference between the onset potential of Ru2+ PEC oxidation by Ta3N5/SiO2 and the redox potential of Ru2+/3+ in the nonaqueous environment was about 0.7 V. While a stable photoanodic response was observed for Ta3N5/SiO2 in the nonaqueous phase, the addition of a small quantity of water into this nonaqueous system led to the immediate deactivation of Ta3N5/SiO2 photoanode under illumination by self-photooxidation to form TaOx at the solid/water interface. In aqueous phase, flatband potentials estimated from Mott-Schottky analysis varied with solution pH (constant potential against reversible hydrogen electrode (RHE)). Photoelectrode modification by a transparent NiFeOx layer was attempted. The complete coverage of the Ta3N5 surface with transparent NiFeOx electrocatalysts, achieved by an optimized spin-coating protocol with controlled Ni-Fe precursors, allowed for the successful protection of Ta3N5 and demonstrated an extremely stable photocurrent for hours without any additional protective layers. The stability of the resultant NiFeOx/Ta3N5/SiO2 was limited not by Ta3N5 but mainly by a NiFeOx electrocatalyst due to Fe dissolution with time.

Effects of Water Content on Physicochemical Properties of a Protic Ionic Liquid with Monoprotic N-Hexylethylenediaminium as Cation and Bis(trifluoromethylsulfonyl) Imide as Anion

The effects of water content on physicochemical properties such as density, dynamic viscosity, and electrical conductivity of HHexen(Tf2N), composed of monoprotic N-hexylethylenediaminium as cation and bis(trifluoromethylsulfonyl) imide as anion, were studied in the temperature range T = 303.15–353.15 K. HHexen(Tf2N) was dissolved a small amount of water (up to 6.53 wt%, corresponding to w0 = [H2O]/[PIL] = 1.65) as it is a hydrophobic protic ionic liquid (PIL). The physicochemical properties of HHexen(Tf2N) were significantly influenced by its water content. The temperature dependence of the physicochemical properties at different water contents (0.50 wt%, 0.95%, 1.93%, 3.02%, 4.03%, 5.14% and 5.95%, corresponding to w0 = 0.12, 0.23, 0.47, 0.74, 1.0, 1.28 and 1.50, respectively) were studied. With an increase in the water content, the density and dynamic viscosity decreases while the electric conductivity increases in a given temperature range. The Walden lines of HHexen(Tf2N) show a good ionic character as the curves are all located in the range of ΔW = 0.5 ± 0.2 (ΔW = log101/η −log10 Λ) at different water contents. The ionicity shows an increasing trend with an increase of water content; this is evident when the water content rises to approximately 4.0% (w0 = 1.0). Additionally, HHexen(Tf2N) was used to extract Co(II) ions from an aqueous solution. Inductive coupled plasma emission spectrometry results showed that more than 99.5 wt% of Co(II) ions moved from the 100 mmol·kg−1 aqueous layer to the HHexen(Tf2N) layer (of equal volume). After extraction of the Co(II) ions, the PIL layer contained 7.90% of water (w0 = 2.0).

Methane coupling and hydrogen evolution induced by palladium-loaded gallium oxide photocatalysts in the presence of water vapor

Non-oxidative coupling of methane (NOCM, 2CH4 → C2H6 + H2) is a reaction that can directly produce ethane and hydrogen at the same time, and gallium oxide (Ga2O3) powder has been reported as an effective photocatalyst for NOCM at room temperature. In this study, we investigated the reaction conditions for Pd-loaded Ga2O3 photocatalysts to improve the production rate of C2H6 and H2. We found that the 0.1 wt% Pd/Ga2O3 exhibited high selectivity of C2H6 (75.8%, carbon-based) under the conditions of steam reforming of methane. Photocatalytic NOCM seems to proceed in the presence of small amount of water. An increase in water vapor pressure (PH2O) was essential for the steady production of C2H6 and H2. The C2H6 production rate was 0.79 μmol min−1 for 50 mg of Pd/Ga2O3 powder at PH2O = 3.6 kPa. The apparent quantum efficiency (AQE) for C2H6 production was 5.1%, which is much higher than that of conventional photocatalytic NOCM in the absence of water vapor. The importance of water adsorbates on the photocatalyst surface was suggested by water vapor adsorption isotherm and Fourier transform infrared (FT-IR) spectroscopy. It is revealed that multilayered water molecules adsorbed on the photocatalyst surface play a role as a reaction field that promotes the dehydrogenative coupling of CH4.

Water-Mediated Reversible Control of Three-State Double-Stranded Titanium(IV) Helicates

A stimuli-responsible reversible structural transformation is of key importance in biological systems. We now report a unique water-mediated reversible transformation among three discrete double-stranded dinuclear titanium(IV) achiral meso- and chiral rac-helicates linked by a mono(μ-oxo) or a bis(μ-hydroxo) bridge between the titanium ions through hydration/dehydration or its combination with a water-mediated dynamic cleavage/re-formation of the titanium-phenoxide (Ti-OPh) bonds. The bis(μ-hydroxo) bridged titanium(IV) meso-helicate prepared from two tetraphenol strands with titanium(IV) oxide was readily dehydrated in CD3CN containing a small amount of water upon heating, accompanied by Ti-OPh bond cleavage/re-formation catalyzed by water, resulting in the formation of the mono(μ-oxo)-bridged rac-helicate, which reverted back to the original bis(μ-hydroxo)-bridged meso-helicate upon hydration in aqueous CD3CN. These reversible transformations between the meso- and rac-helicates were also promoted in the presence of a catalytic amount of an acid, which remarkably accelerated the reactions at lower temperature. Interestingly, in anhydrous CD3CN, the bis(μ-hydroxo)-bridged meso-helicate was further slowly converted to a different helicate, while its meso-helicate framework was maintained, namely the mono(μ-oxo)-bridged meso-helicate, through dehydration upon heating and its meso to meso transformation was significantly accelerated in the presence of cryptand[2.2.1], which contributes to removing Na+ ions coordinated to the helicate. Upon cooling, the backward meso to meso transformation took place via hydration. Hence, three different, discrete double-stranded chiral rac- and achiral meso-titanium(IV) helicates linked by a mono(μ-oxo) or a bis(μ-hydroxo) bridge were successfully generated in a controllable manner by a change in the water content of the reaction media.

The effect of increasing water content on transition metal speciation in deep eutectic solvents

A move towards the use of green solvents in metal recovery processes is going to be necessary for the development of a sustainable circular economy. This paper determines the effect of adding water to choline chloride based deep eutectic solvents on transition metal speciation, a common method for reducing their viscosity, using UV/Vis absorption spectroscopy. Even small amounts of water (< 5 %) were seen to cause a hypsochromic shift in UV/Vis spectra, indicating a change in metal speciation. In the choline chloride – urea solvent, the hydrolysis of the studied metals (V3+, Fe3+, Ni2+, Co2+, Cu2+) was observed. In the ethylene glycol and malonic acid systems precipitation was not observed, and Mx+ − H2O interactions were generally seen to dominate above ca. 30 % H2O. The presented results will impact metal recovery process design, where water additions to deep eutectic solvents to lower viscosity must be balanced with changes in metal speciation. This will allow for optimization of pumping systems whilst maintaining an effective process.

Application of Car Fire Blankets to Car Fires

Recently, car fires have been occurring on city roads (47.3%) and expressways (17.2%). Depending on the traffic conditions on the road, the growth of these fires can be delayed until firemen or a pump car arrives at the scene. In this study, application and utilization methods were derived based on car fire extinguishing experiments. To this end, a suffocation effect was induced using a car fire blanket and without using water in the event of a car fire. A car was ignited, and the car fire blanket was applied for 10, 20, and 30 min during the peak of the fire to verify whether the fire could be extinguished. A partial fire was caused for the three experiments, which could be put out with a small amount of water. Based on the results of these experiments, i.e., car fires can be put out using a car fire blanket and an on-site utilization plan, a new technology is presented.

Solid-liquid interaction caused by minor wetting in gravel-ice mixtures: A key factor for the mobility of rock-ice avalanches

Rock-ice avalanches pose serious risks to humans and infrastructures due to their extremely large volumes and high mobility in glacierized mountain regions. The mobility of rock-ice avalanches is supposed to be influenced by water, while the solid-liquid interactions induced by minor wetting remain an open issue. A series of flume tests was performed to investigate the influence of a small amount of water (no more than 4% of the gravel weight) on the behavior and mobility of gravel-ice mixtures. The test results show that intergranular refreezing bonds were created with a preliminary addition of water. The breakup of some weak refreezing bonds during particle rearrangement likely dissipated some kinetic energy, and thus, the mixture mobility was reduced. As the water content increased, the thermal conductivity could likely not remain efficient enough to refreeze all the trapped water and thus allowed unfrozen water to lubricate particle corners, which enhanced mixture mobility. With a further increase in the water content, suction-induced cohesion cemented particles as clusters and reduced mixture mobility. However, a high ice content resulted in mobility enhancement with increasing water content because more gravel was refrozen into the ice matrix, and thus, the basal friction was lowered by the occupation of ice cubes at the bottom. The redistribution pattern of trapped water during mass propagation changed at a characteristic water content. When the water content was lower than the characteristic content, superficially cohered water detached from the surface asperity of one particle and transferred to another during particle rearrangement, i.e., local redistribution of trapped water. When the water content was higher than the characteristic content, the downward transfer of a considerable amount of trapped water was triggered by particle rearrangement under the influence of gravity, i.e., bulk redistribution of trapped water. The water experiencing bulk redistribution influenced the mixture mobility by exerting intergranular drag force via the build-up and break-up of liquid bridges, while locally redistributed water influenced mixture mobility by altering the surface properties of particles. This study is expected to be helpful in better understanding the propagation mechanisms of water-poor rock-ice avalanches and in improving relevant hazard assessments. • Water influence on rock-ice avalanche mobility was studied via a small flume test. • Lubrication of unfrozen water enhanced mixture mobility. • Suction-induced cohesion reduced mixture mobility. • The refreezing of minor trapped water might reduce mixture mobility. • Water redistribution pattern changed at a typical water content of 2.2%.

Properties of Compressed Interlock Earth Blocks Manufactured from Locally Available Lateritic Soil for Low Cost Housing Projects

This investigation was carried out to identify the engineering properties of compressed interlock earth blocks manufactured from locally available lateritic soil and introduce to use the manufactured soil blocks to minimize the material and finishing cost for the low cost housing projects. The soil samples used in this study were well-graded lateritic sandy soil which has the composition of 1.9% gravel, 94% sand and 4.1% silt / clay. These soil samples were passed through the 100-mesh sieve and mixed with ordinary Portland cement to prepare the admixture. While compressing through a hydraulics jack by varying the compositions and the volume of soil-cement admixtures, compaction soil blocks were manufactured in a locally fabricated 250 mm x125 mm x100 mm standard steel mould. The manufactured soil blocks allowed to cure while spraying small quantity of water and covering with polythene for 28 days. Average compressive strengths of soil blocks made with 5% cement with 1.6:1 and 1.8:1 volume compactions were 1.3 Mpa and 1.9 Mpa, respectively. However, both compressive strength values were less than the standard limits of 2.8 MPa stated in SLS 1382:2009, local standards for soil blocks used for construction industry. However, soil blocks made with 10% cement under same compaction ratios attained compressive strengths of 3.0 MPa and 3.6 MPa respectively and it is above the required standards limits. However, 15% and 20% cement containing earth blocks have much higher compressive strengths but increase the cost of production. Regression analysis results confirmed the strong correlation between cement content and the compressive strength of the soil bricks. The soil bricks manufactured with more than 12.06% cement soil mix by maintaining compaction ratio into 1.6:1 or Soil bricks manufactured with more than 5.16% cement mix by maintaining compaction ratio into 1.8:1 will produce standards soil bricks for construction industry and these results further confirmed that wet and dry compressive strength of soil bricks will increase with increasing the compaction ratio and the cement content. However, when considering the compressive strength, water absorption level and cost effectiveness, soil bricks manufactured by maintaining compaction ratio into 1.8:1 with more than 5.16% cement mix will produce required standards cost effective soil bricks for construction industry.