Addition Of Sand Particles Research Articles

Unveiling the temperature-dependent mechanisms of viscoelasticity of sand-enhanced epoxy

The viscoelastic behavior of epoxy is critical for its engineering performance and applications. This work focused on the improvement of its viscoelastic performance by using natural sand particles as fillers. Experiments were carried out to investigate the static and dynamic viscoelastic properties of epoxy with various sand particle contents. Static mechanical tests demonstrated an increase in the elastic modulus, albeit at the cost of reduced strength at a higher sand content due to stress concentrations. Dynamic tests indicated substantially improved storage modulus and damping of epoxy after being filled with sand particles. Moreover, the glass transition temperature of epoxy showed a substantial rise upon the addition of sand particles, signifying an augmentation in its heat resistance. Static viscoelastic characterization revealed an elevation in both room- and high-temperature relaxation moduli upon incorporating sand. By applying time–temperature superposition principles, long-term relaxation curves were obtained, which could provide a reference for engineering design. These viscoelastic investigations offer insights into the underpinning mechanisms governing the performance of sand-reinforced epoxy. This enables the rational design of sand-particle-reinforced epoxy for customized durability, heat resistance and vibration damping.

Scaling law of the second-order structure function over the entire sandstorm process

This study reveals the competitive evolutionary process of the main driving factors in the early, middle and late stages of sandstorms, as shear turbulence becomes dominant and is then suppressed by enhanced thermal stability, based on quadrant analysis of the sand-laden turbulent wind field acquired from field observations over the entire sandstorm process. Moreover, the self-organized state of multiscale structures in the energy-containing region of the sand-laden turbulence is found to change significantly as the sandstorm develops. The logarithmic scaling law that governs the cumulative turbulent kinetic energy for the non-stationary flow in the early and late stages of the sandstorm is different from the existing theoretical formula. The corresponding rate of increase in the cumulative kinetic energy with increasing scale is much higher in these stages than in the middle stage of the sandstorm with steady flow. The change in self-organized state of turbulence is responsible for the flow acceleration and the thermal superimposed effect, rather than the addition of sand particles.

The effect of mixing molar ratios and sand particles on microstructure and mechanical properties of metakaolin-based geopolymers

In this study the influence of the molar ratios such as SiO2:Al2O3:Na2O:H2O, as well as the sand particles on the mechanical performance, shrinkage and microstructure of metakaolin based geopolymers was studied. Considering different content of the reactive silica and alumina in metakaolin, forty eight different compositions were prepared. The proper condition for achieving the highest mechanical performance as well as less structural defects by tailoring the curing condition, molar ratios and addition of sand particles are presented. Special attention was paid to the incorporation of sand particles up to 70 wt% on the microstructure, shrinkage and mechanical properties of metakaolin based geopolymers. Results from mechanical testing and microstructural observations revealed that replacing metakaolin with 30 wt% sand particles can significantly reduce drying shrinkage and improve compressive and flexural strength. It was suggested that this strengthening is probably due to a partly reactive sand/matrix interface as well as stacking of filler particles and their ability to carry load and limit crack growth. Comparison of the compressive and flexural strength between geopolymer and cement mortars containing up to 50 wt% sand, revealed that the strength of geopolymer specimens were at least three times more than that of cement.

Bioremediation of Oil Contaminated Soils by Washing under Static Conditions (Research Note)

In this research five different solutions were used to wash an oil contaminated soil with the initial TPH (Total Petroleum Hydrocarbon) content of 46 g kg-1 (grams of TPH per kg of dry soil). The solutions were a basal mineral medium (solution I), the basal mineral medium inoculated with petroleum degrading microorganisms (solution II), the basal mineral medium inoculated with a culture of petroleum degrading microorganisms and supplemented with a commercial washing powder (solution III), the basal mineral medium inoculated with the microorganisms and supplemented with Tween 80 (solution IV), and the basal mineral medium inoculated with the microorganisms and supplemented with sucrose (Solution V). Washing was performed by saturation of the soil with the solutions in columns and intermittent mixing. Solutions IV and V performed better than the others, giving more than 90% TPH removal in two months. In a separate experiment TPH removal was monitored as a function of time during washing. Solution V reduced the TPH content of the soil more rapidly than the others, with more than 70% TPH removal in 28 days. Addition of sand particles to the soil for the purpose of better mixing resulted in marginal positive effects.

Enhanced bamboo composite with protective coating for structural concrete application

Potential application of newly developed bamboo composite material as structural reinforcement called forth for durability test and bond strength examination. Firstly, durability of bamboo composite material and effectiveness of protective epoxy coating were evaluated by subjecting samples to various corrosive environments normally encountered during the life span of construction materials. At accelerated conditions, samples were immersed in water, simulated acidic rain solution and simulated concrete pore water solution for 28 days. Tensile tests and microstructural analysis were conducted to investigate the impact of different corrosive environments on the bamboo composite material’s behavior. The results revealed that the application of epoxy coating successfully protected bamboo composite material’s integrity without substantially affecting its mechanical capacity, particularly in acidic environment. Secondly, bond strength between bamboo composite material and concrete was investigated through pull-out tests. The epoxy coating improved the bond strength, especially with addition of sand particles. The findings of this study suggest that epoxy coating can be an effective approach to simultaneously enhance the bamboo composite material’s resistance towards acid attack and improve its bond strength with concrete for concrete reinforcement application.

Fluidization Behavior of Biomass Particles and its Improvement in a Cold Visualized Fluidized Bed

The fluidization behavior in a fluidized bed was visualized at room temperature under different conditions for two typical lignocellulosic biomass materials (rice husk and walnut shell) as representative samples of herbage and xylophyta, respectively. The effects of initial bed height, moisture content, and addition of sand particles on the quality of fluidization were analyzed, and the optimal operating parameters were determined. The initial bed height had a negligible effect on the minimum fluidization velocity but an obvious influence on bed stability. In addition, with an increase in moisture content, the minimum fluidization velocity showed the growth of an S-shaped curve and a constant decrease in the fluidization index in the fluidized region. Fluidization when performed on binary mixtures indicated that the proportion of sand-3 (60 to 80 mesh) in biomass and sand-3 in mixtures is a main factor contributing to the fluidizing quality of a bed. With larger proportions of sand-3, the fluidizing quality of the bed improved. Meanwhile, the differences in fluidization behavior between rice husk and walnut shell have been determined.

Corrosion Resistance of a Sand Particle-Modified Enamel Coating Applied to Smooth Steel Bars.

The protective performance of a sand particle-modified enamel coating on reinforcing steel bars was evaluated in 3.5 wt% NaCl solution by electrochemical impedance spectroscopy (EIS). Seven percentages of sand particles by weight were investigated: 0%, 5%, 10%, 20%, 30%, 50% and 70%. The phase composition of the enamel coating and sand particles were determined with the X-ray diffraction (XRD) technique. The surface and cross-sectional morphologies of the sand particle-modified enamel coating were characterized using scanning electron microscopy (SEM). XRD tests revealed three phases of sand particles: SiO2, CaCO3 and MgCO3. SEM images demonstrated that the enamel coating wetted well with the sand particles. However, a weak enamel coating zone was formed around the sand particles due to concentrated air bubbles, leading to micro-cracks as hydrogen gas pressure builds up and exceeds the tensile strength of the weak zone. As a result, the addition of sand particles into the enamel coating reduced both the coating and corrosion resistances.

Synergistic effects of fluid flow and sand particles on erosion–corrosion of aluminum in ethylene glycol–water solutions

The synergistic effects of fluid flow and sand particles on erosion–corrosion of 3003 aluminum (Al) alloy in ethylene glycol–water solution that simulates the automotive engine coolant were studied through a rotating disk electrode by electrochemical measurements. It was found that, in the absence of sand particles, the anodic current density of Al electrode decreases with the increase in electrode rotating speed, which is attributed to the enhanced electrode oxidation accompanying with accelerated oxygen diffusion and reduction. Mass-transport plays an important role in electrode process, as indicated by the presence of diffusive impedance. With the addition of sand particles, the de-stabilization of electrode is predominant and the anodic current density increases with the electrode rotation speed, which is attributed to the enhanced impact damage to electrode by sand particles. The electrode roughening effect due to sand impact is indicated by the presence of inductive loop in impedance plots. The variation of sand particle size does not have apparent effect on polarization behaviour of Al electrode, while an elevated temperature increases significantly the anodic current density of the electrode. There exists a synergism of fluid flow and sand impact on electrochemical corrosion behaviour of Al electrode.

Erosion — corrosion of duplex stainless steel under Kuwait marine condition

Erosion — corrosion of stable passive metals like Duplex Stainless Steels (DSS) proceeds by the repeated removal and repair of the oxide film. When sand particles are entrained it can be a problem in marine pumps, piping systems, heat exchangers, and units handling seawater in the Arabian Gulf for use as part of desalination plants. More specifically, sand particles in the presence of seawater enhanced the erosion corrosion problem. If the passive film structure is stable, it will reform spontaneously when it becomes damaged. The erosion-corrosion study is concerned with the application of a jet impingement apparatus to study the behavior of DSS steel of Cr/Ni/Mo/N grade in simulated Arabian Gulf seawater. An interference color imaging technique (ICI) for thickness measurement of the oxide film passivity, pitting, and transpassivity of the surface of DSS has been developed under the effect of well defined hydrodynamic condition and potentiodynamic polarization technique. Electrochemical imaging technique of surface corrosion potential mapping (SCM) was also introduced to measure the rate of repair of the passive film combined poteniodynamic polarization under flowing conditions, both with and without the addition of sand particles. The main aim is to obtain a better understanding of the electrochemistry of DSS alloys in marine erosion–corrosion condition and to examine the viability of SCM and ICI to be used as a diagnostic tool for DSS material evaluation. The results indicated that both techniques gave optimum imaging analysis of DSS steel. Water jet impingement showed higher current densities at the ferrite dissolution potential and austenite pitting potential during the introduction of sand particles.

Effects of alumina particle dispersion on the erosive–corrosive wear response of a zinc-based alloy under changing slurry conditions and distance

This investigation analyses the influence of dispersed alumina particles on the wear behaviour of a zinc-based alloy in a slurry, comprising suspended sand particles. The influence of the sand content (in the slurry) and travel distance on the wear characteristics of the samples was also studied. Wear rate increased initially with distance, attained a peak, decreased thereafter, and finally, attained a steady-state value at longer distances. These stages were more defined when tests were conducted in the liquid (electrolyte) medium without sand. Addition of sand particles in the electrolyte reduced the wear rate of the specimens. It was also observed that when tests were conducted in the electrolyte plus sand (i.e., slurry with sand), wear rate first increased with the sand content (of the electrolyte), attained a maximum at an intermediate sand concentration, and then finally, decreased as the concentration of sand particles was increased further. The composite showed better wear resistance than the matrix alloy in general. The observations have further been substantiated through the examination of wear surfaces and subsurface regions of the samples. Wear response of the samples has been explained on the basis of (i) predominance of the operating mechanisms of material removal such as corrosive, erosive and abrasive wear under a given test condition, and (ii) the nature and properties like corrosive nature, hardness and interfacial characteristics of the various microconstituents of the samples. The study suggests that the predominance of one or more of the mentioned (material/experimental) parameters basically controls the wear behaviour of the specimens, and that the nature of their contribution is further governed by the specific test conditions.

Laboratory Analysis of Mudflow Properties

A rotational viscometer has been designed for laboratory measurements of the rheological properties of natural mudflow deposits in Colorado. The mudflow matrices comprised of silt and clay particles are sheared under temperature-controlled conditions at volumetric sediment concentrations ranging from 0.10 – 0.45. This study stresses the importance of conducting rheological measurements at low rates of shear because: 1) Those are the conditions found in natural channels; and 2) they avoid the slippage problems observed at large sediment concentrations. At low rates of shear, the Bingham model is fitted to the measured rheograms, and both the viscosity and yield stress increase exponentially with the sediment concentration of the fluid matrix. Both the yield stress and the viscosity increase by three orders of magnitude as the volumetric concentration of sediments in the fluid matrix changes from 10% to 40%. The addition of sand particles does not significantly alter the rheological properties of the matrix unless the volumetric concentration of sands exceeds 0.20.