Expanded Polystyrene Particles Research Articles

Prediction of compressive strength and elastic modulus of expanded polystyrene lightweight concrete

Expanded polystyrene (EPS) lightweight concrete is composed of a plain concrete matrix and EPS beads. The aim of the study was to characterise the mechanical properties of EPS lightweight concretes containing various volumes of EPS (0%, 5%, 10%, 15%, 20%, 25%, 30%, 35% and 40%) and of two water/cement ratios (0·45 and 0·55). The test results indicate that the apparent density, compressive strength, splitting tensile strength and elastic modulus of EPS concrete decrease when the content of EPS particles increases. Based on the experimental results and composite approach, a new simplified mathematical model is proposed for evaluating the compressive strength and elastic modulus of EPS concrete as a function of the mechanical properties of the plain concrete, the mechanical properties of the EPS and the percentage of EPS particles.

Sintering preparation of porous sound-absorbing materials from steel slag

Porous sound-absorbing materials were prepared from steel slag using waste expanded polystyrene (EPS) particles as pore former. The influences of the experimental conditions such as fly ash content, sintering temperature, sintering time, and pore former addition on the performance of the porous sound-absorbing materials were investigated. The results show that the porosity of the specimens can reach above 50.0%; the compressive strength and average sound-adsorption coefficient of the sintered specimens are above 3.0 MPa and 0.47, respectively. The optimum preparation conditions for the steel slag porous sound-absorbing materials are as follows: mass fraction of fly ash 50%, waste EPS particles 3.6 g, sintering temperature 1100 °C, and sintering time 7.5 h, which are determined by considering the properties of the sound-absorbing materials, energy consumption and cost.

Prescription Formula of Foamed Particles in Lightweight Soil

To research the prescription of lightweight soil under an optimum water content condition, the influence of the water content on the material state should be completely removed. The optimum water content of different mixing ratios of lightweight soil can be obtained using the optimum water content model. The prescription formula and prescription optimization method of foamed particle lightweight soil were investigated using density tests and unconfined compressive strength tests. The results show that the density of lightweight soil is mainly affected by the content of expanded polystyrene (EPS) particles, and it decreases linearly with an increase in the EPS particle volume ratio. However, the effect of the cement content on the density of lightweight soil is very small and can be ignored. The unconfined compressive strength of lightweight soil increases linearly with the increase in cement content, and the strength growth rates are mainly affected by the different EPS particle contents. There is a minimum cement content; if the cement mixing ratio is lower than the minimum cement content, there will be no solidification effect for the cement. The unconfined compressive strength of lightweight soil decreases linearly with an increase in the EPS particle volume ratio, and the strength reducing rates are mainly affected by the different cement contents. There is a maximum content for the EPS particles; if the EPS particle volume ratio is more than the maximum content of EPS particles, the strength of the mixed soil will be completely lost. Considering the density, strength, and cost of mixed soil, two empirical prescription formulas were proposed: the positive correlation linear fitting method and the negative correlation linear fitting method.

Experimental study of the influence of EPS particle size on the mechanical properties of EPS lightweight concrete

Expanded polystyrene (EPS) concrete is a new lightweight building material that exhibits good mechanical properties and a priori mechanical features that are suitable for the construction industry. The mechanical properties of EPS concrete were determined to be related to the concrete matrix and particle size of EPS. The compressive strength, tensile strength and flexural strength of EPS concrete with different size of EPS particles were compared in this paper. Based on the results of the compressive strength tests, a compressive strength expression was proposed. Ultrasonic testing was performed during the processes of loading up to uniaxial compressive failure. The ultrasonic testing results indicated that the mechanical properties of EPS concrete are related to the EPS particle size and the granules content and that the ultrasonic testing method can detect damage of EPS concrete during the loading process.

Durability of expanded polystyrene mortars

The influence of the addition of various types and various concentrations of expanded polystyrene foam (both commercial and recycled) on the durability of Portland cement mortars is studied. In particular, the microstructure is studied utilizing the following methods: capillary absorption of water, mercury intrusion porosimetry, impedance spectroscopy and open porosity. In addition, the effects of heat cycles and freeze–thaw cycles on compressive strength are examined. Scanning electron microscopy is used as a complementary technique. An air-entraining agent, water retainer additive and superplasticizer additive are used to improve the workability of mortars. The results show that the presence of expanded polystyrene in mortar results in a decrease in the capillary absorption coefficient. The mercury intrusion porosimetry technique and the equivalent circuits previously used by researchers to interpret impedance spectra of ordinary cementitious materials were found to be inadequate for interpreting the microstructure of mortars with expanded polystyrene. This is due to the polymeric nature as well as the internal porous structure of expanded polystyrene. A slight increase of compressive strength is observed in mortars with expanded polystyrene subjected to heat cycles. The compressive strength of mortars subjected to freeze–thaw cycles likely improves because expanded polystyrene particles absorb part of the pressure of ice crystallization. It is concluded that the durability of mortars improve with the presence of expanded polystyrene, making them viable for more sustainable usage in masonry, stucco and plaster mortars.

ワンド水表面における浮遊物質の主流部への輸送速度に関する研究

Recently, maintaining biodiversity in rivers is required as a part of nature-oriented river works. Wandos made artificially in rivers are one of the measures to secure biodiversity. Transport of suspended solids at the water surface of wandos to river stream is known to be controlled by large scale vortices.In this study, firstly transport rates of expanded polystyrene particles as uspended solids at the water surface of a wando in a rectangular channel were examined. The results of experiments in the rectangular channel indicate that the transport rate of expanded polystyrene particles decreases with the increase in Froude number. Secondly, a formula on the transport of expanded polystyrene particles was proposed as a function of Froude number and the ratio between the length and the width of wando.

Infinite Penetration of a Projectile into a Granular Medium

An object falling in a fluid reaches a terminal velocity when the drag force and its weight are balanced. Contrastingly, an object impacting into a granular medium rapidly dissipates all its energy and comes to rest always at a shallow depth. Here we study, experimentally and theoretically, the penetration dynamics of a projectile in a very long silo filled with expanded polystyrene particles. We discovered that, above a critical mass, the projectile reaches a terminal velocity and, therefore, an endless penetration.

Millimeter wave electromagnetic interference shielding by coating expanded polystyrene particles with a copper film using magnetron sputtering

Expanded polystyrene (EPS) particles were coated with copper by magnetron sputtering in order to produce a material suitable for electromagnetic interference (EMI) shielding. Field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysis (EDS) results demonstrated the effectiveness of successful copper deposition. The EMI shielding effectiveness (SE) of the Cu-coated EPS particles was measured to be 14–39 dB over a frequency range of 80–110 GHz, suggesting that Cu-coated EPS particles can be used as an effective lightweight millimeter wave EMI shielding material.

Performance of expanded polystyrene particles in deep bed filtration

The efficiency of filtration through a bed of expanded polystyrene (EPS) of different characteristics was investigated on the example of separation of iron hydroxide flocks from water. The effects studied included the EPS density, bed equivalent diameter, and bed uniformity coefficient. Studies by scanning electron microscopy showed that surface roughness of EPS particles is primarily determined by particle density. Low-density EPS particles have higher roughness than the high-density ones, and this fact has a great effect on the filtration cycle. Low-density particles yield a low head loss and long filtration cycle, which decrease with increasing particle density. As far as the bed equivalent diameter is concerned, only a small increase in particle size of the existing particle formulation decreases significantly the filtration cycle. It is very important to notice that similar bed equivalent diameter can be achieved by mixing different particle fractions, changing at the same time the uniformity coefficient. That is the reason why we investigated the effect of uniformity coefficient and showed that there exists its optimum value, yielding a maximum filtration cycle. Our investigation showed that the uniformity coefficient is of crucial importance in the optimization of EPS bed filtration.

Floating photocatalysts based on TiO 2 grafted on expanded polystyrene beads for the solar degradation of dyes

In this work, a highly active, low cost, simple and robust floating photocatalyst based on TiO 2 P25 grafted on expanded polystyrene (EPS) beads was developed. SEM and TG analyses showed that ca. 18 wt% of TiO 2 can be permanently grafted on the surface of EPS particles. This floating photocatalyst showed high efficiency for the degradation of three different dyes, i.e. methylene blue, indigo carmine and drimaren red, with UV (Hg 245 nm) or solar irradiation under constrained conditions, i.e. non-stirring and no-oxygenation. Under the same conditions pure TiO 2 showed very low activities. The floating photocatalyst can be reused for at least four consecutive times without any significant decrease on the discoloration and TOC removal after each reuse.

21013 空中超音波を用いた非接触マニピュレーション(原子力と材料・構造・組織(3),OS.4 原子力と材料・構造・組織)

A noncontact manipulation technique is useful for micromachine technology. In this paper, we describe an advanced manipulation technique for trapping and transporting small objects in air. A standing wave field was generated by two sound beams crossing each other generated by bolted Langevin transducers. Expanded polystyrene particles were trapped at the nodes of the sound pressure in the standing wave field. The position of a trapped particle was shifted by changing the phase difference between the two sound beams. The force was culated from the sound pressure distribution by Rayleigh's formula. The calculated result agrees with the experimental data.

Noncontact Acoustic Manipulation in Air

A noncontact manipulation technique is useful for micromachine technology, biotechnology, and new materials processing. In this paper, we describe an advanced manipulation technique for transporting small objects in air. A standing wave field was generated by two sound beams crossing each other generated by bolted Langevin transducers. Expanded polystyrene particles were trapped at the nodes of the sound pressure in the standing wave field. The position of a trapped particle was shifted by changing the phase difference between the two sound beams. When the trapped particle is transported, it spatially oscillate periodically in a direction perpendicular to that of particle transportation. The numerical calculation of an acoustic field revealed that it is caused by the reflection of an ultrasonic wave at each transducer surface.

Mechanical properties of polymer-modified concretes containing expanded polystyrene beads

In this study, styrene-butadiene rubber (SBR) latex as a polymeric admixture was applied in lightweight expanded polystyrene (EPS) concrete. The effects of curing conditions and polymer-cement ratio on the compressive and flexural strengths of polymer-modified EPS concretes were investigated. As a result, the strength development of the polymer-modified EPS concretes strongly depends on the curing conditions. Combined dry and wet curings enable to develop both the strengths of cement matrix and SBR films together. Inclusion of SBR latex at a certain polymer-cement ratio in the EPS concrete improves the bonds between the cement matrix and EPS particles due to the SBR films formed in the cement matrix. In addition, SBR modification can significantly improve the flexural strength of the normal EPS concrete. Compared with the EPS concrete, the compressive strength of the polymer-modified EPS concretes can increase gradually even after 28 days.

Local shear and skin friction on particles in three-phase fluidized beds

An extension of the electrochemical shear-rate measurement technique is carried out in this work to evaluate the friction force and the shear stress on a particle in two and three phase fluidized beds. Using this technique, the skin friction on a sphere has first been validated for single phase flow. In two- and three-phase fluidized bed, the significance and the direction of the velocity gradient at the wall are discussed. In the case of three phase fluidization, glass spheres (2 mm in diameter, ρ s = 2532 kg m - 3 ) and plastic spheres (5 mm in diameter, ρ s = 1388 kg m - 3 ) were used. This choice provides very different bubbly flows due to different balances of coalescence and break-up of bubbles The contribution of the frictional force is more important in “coalescent” fluidized beds than in “break-up” fluidized beds. The effect of gas injection is depending on the fluidized particle effect on bubble coalescence and break-up. Correlations have been developed linking frictional force to gas hold-up. The correlations recommended for frictional force in fluidized beds for both systems, (i.e., coalescence and break-up) are as follows: • Glass spheres (2 mm diameter, coalescence regime): F = 2.43 Re 0.052 ɛ g 0.4 , standard deviation = 6 % . • Plastic spheres (5 mm diameter, break-up regime): F = 0.123 Re 0.3 ɛ g 0.1 , standard deviation = 4 % . F is a dimensionless force defined by F = F f / P a , where P a is the effective weight of the sphere. In the case of inverse fluidization, where the solid phase consisted of expanded polystyrene particles 5 mm in diameter ( ρ s = ( 350 – 550 ) kg m - 3 ) , the average frictional force remains almost unaffected by gas injection due to opposite effects on terminal particle velocity and on turbulence.

Order and disorder in particle?liquid flows in a pipe

The spherical expanded polystyrene particle–oil two-phase flow in a vertical pipe was used to simulate the dispersed phase distribution in laminar bubbly flows. A three-dimensional particle image tracking technique was used to track the particles in the flow to study the ordered structure of dispersed phase distribution and its transition to disorder. The ordered structures behaved as particle strings aligned in the flow direction as induced by the flow shear. The structures were quite durable in high liquid velocity flows and dispersed gradually as the liquid velocity decreased. In lower velocity flows, the particles tended to form clusters in the horizontal direction, as predicted by potential theory for spherical bubbles rising in a quiescent inviscid liquid and as observed in experiments on non-shear bubbly water flows.

Laminar light particle and liquid two-phase flows in a vertical pipe

Dilute laminar expanded polystyrene particle–oil flows in a vertical pipe were studied using a three-dimensional particle image tracking (PIT) method. The particle volume fraction profiles and other flow properties for the upward fully developed flows were measured. The experimental results showed that the particles in both the large and small particle and oil flows have a wall-peaked distribution similar to those of near-spherical bubbles in laminar bubbly flows. The ordered particle distribution structure consisting of particle clusters and its transition to disordered flow structures were observed. Comparisons between the bubble and particle volume fraction profiles indicate that the major difference of two-phase flow properties may result from bubble deformation.

Nonwetting flow of a liquid through a packed bed with gas cross-flow

In this study, the effect of a cross-flow gas field on the percolating flow of a non-wetting liquid through a packed bed was investigated. Experiments were conducted to measure the liquid shift, due to the cross-flow of air, for the flow of aqueous barium chloride solutions and mercury percolating through beds of polyethylene and expanded polystyrene particles. An X-ray technique was used to visualize the liquid flow pattern through the packed bed. The liquid percolates through a packed bed as a series of rivulets and droplets which are continuously breaking up and coalescing. A mathematical model to predict the direction of the liquid rivulet/droplet flow under the influence of a gas flow field was developed. The model treats the liquid as a discrete phase and includes the effects of gravity, gas drag, and inertial and viscous bed resistance. The effective droplet/rivulet size is an important model parameter, and the model postulates that the droplet/rivulet size is a function of both the effective capillary size of the bed and the liquid flow rate. A simplified population balance analysis for droplet coalescence is used to predict the effect of liquid flow rate on droplet/rivulet size. The model predictions are consistent with the experiments.

Phase distribution and turbulence structure for solid/fluid upflow in a pipe

The phase distribution and turbulence structure for solid/fluid upflow in a vertical pipe were investigated. Spherical particles, approximately 2 mm in diameter, were used and runs were made with particles having two different specific gravities. In particular, ceramic particles, which were heavier than water, and expanded polystyrene particles, which were lighter than water, were used. A new method is presented for the measurement of the volume fraction in solid/fluid two-phase flows using a laser-Doppler anemometer (LDA). The measured local time fractions obtained with the LDA must be corrected, because bias is produced by the presence of natural seeding, the finite size of the measurement volume and interruptions of the laser beams by the dispersed particles. An analytical method has been developed which accounts for these effects. A single-beam traversing γ-ray densitometer was used as a reference against which to assess the volume fraction correction method. Good agreement between the the corrected LDA and γ-ray densitometer results was obtained. The volume fraction profiles show that at low flow rates the ceramic particles have an almost uniform distribution, while increasing the flow rate causes coring. In contrast, the phase distribution of the light polystyrene particles had wall peaking for both the low and high flow rates. However, wall peaking was flattened as liquid flow rate was increased.