Expanded Polystyrene Particles Research Articles

Preparation of Hydrophilic and Fire-Resistant Phytic Acid/Chitosan/Polydopamine-Coated Expanded Polystyrene Particles by Using Coating Method

Preparation of Hydrophilic and Fire-Resistant Phytic Acid/Chitosan/Polydopamine-Coated Expanded Polystyrene Particles by Using Coating Method

Research and simulation of electromagnetic wave absorbing performance for lightweight cement-based materials containing expanded polystyrene with different particle sizes and carbon black

The electromagnetic wave (EMW) absorbing performance of cement-based materials incorporating expanded polystyrene (EPS) with varying particle sizes is comprehensively studied through a combination of experimental and simulation methods. The addition of conductive carbon black (CB) to the cement matrix significantly increases the conductivity and dielectric constant, thereby improving the loss capacity. The frequency shift behavior of single and three-layer absorbing materials adheres to the effective medium theory and interference cancellation principle. The enhancement in overall EM parameters leads to a shift of the reflection loss (RL) peak towards lower frequencies. For three-layer materials, an increase in the thickness of absorbent layer proves beneficial for enhancing absorption performance. Simulations can effectively model cement-based materials by employing uniform material settings, with the size of EPS particles serving as the primary variable. The simulation results reveal that an increase in EPS particle size, in both single-layer and multi-layer materials, causes a shift of the RL peak towards lower frequencies. Additionally, analysis of electric field mode distribution and EM power loss density distribution indicates that scattering at the curved EPS interface alters the propagation direction of EMWs, increasing opportunities for loss inside the cement-based material. Moreover, the three-layer absorbing material, with a density ranging from 850 to 900 kg/m3 and compressive strength exceeding 4 MPa, is suitable for EMW absorption in building envelope structures. In conclusion, an increase in EPS particle size and CB content leads to a low-frequency shift of the RL absorption peak. This discovery not only provides an empirical foundation for the development of absorption materials tailored to specific frequency bands but also offers an efficient approach for repurposing waste EPS of diverse sizes. Furthermore, the grading of EPS with different particle sizes has important practical significance for increasing the content of EPS and preparing lightweight cement-based materials.

Experimental study on Corn Straw Fiber (CSF) toughening EPS concrete

The natural Corn Straw Fiber (CSF), it has the advantages of light weight, high strength, good toughness and renewable, can delay the cracking and improve the toughness of cement-based materials. The effects of different mass fractions of CSF and Expanded-Polystyrene (EPS) particles on the compressive strength, flexural strength, splitting tensile strength and their failure modes, load-displacement curves and toughness of EPS concrete were analyzed by full factorial experimental design method. The compressive toughness index (I0, I1) and fracture energy (Gf) were defined to evaluate the effect of CSF on toughening EPS concrete. The results show that the addition of CSF can improve the compressive strength, flexural strength and cracking toughness of EPS concrete to a certain extent. The maximum compressive strength occurred in the E1F3 specimen with a CSF content of 3 % in Group I, which was 1.12 MPa, and the improvement rate was also the highest among the four groups, reaching 69.7 %. The compressive toughness index I1 also reached its maximum in the E1F3 specimen; The maximum flexural strength occurred in the E3F4 specimen with a 4 % CSF content in Group III, which was 0.885Mpa, with the highest improvement rate of 127.38 %. The maximum fracture energy Gf reached 0.827 in the E3F4 specimen. However, another additive, EPS particles, did not significantly improve the physical and mechanical properties of concrete. According to the SEM images and toughening mechanism analysis, it was discovered that tight adhesion between EPS particles and CSF with cement matrix, and the failure mode of CSF was tensile fracture, which could maximize the effect of CSF high tensile toughness. On the basis of mechanical properties and toughening effect, the relationship formulas between variable factors and strength, toughness index were fitted, and the optimal content of EPS and CSF were determined to be 1.3 % and 3 %, respectively.

Hygrothermal performance of micro inhomogeneous insulation materials - EPS-based wall panel

Presence of water in liquid or vapor form leads to mold growth in building materials, weakening the building's structural integrity. Excess moisture in non-breathable materials also impacts thermal properties and performance over time. Hygrothermal analysis and understanding moisture movement within walls are crucial for comprehending wall assemblies in the enclosed spaces of buildings. Numerous commercial software packages are available for estimating moisture risk in wall assemblies. However, it's essential to recognize that these software tools are primarily designed for conventional insulation walls and may not be suitable for materials like EPS-based concrete, which incorporate expanded polystyrene particles. Since micro-level analysis of moisture flow is largely unexplored, this study used mass diffusion theory with ABAQUS-CAE. The study found that EPS beads increased moisture levels in walls by 2-6%. Additionally, due to the porous nature of concrete, moisture penetration and fluctuations were lower compared to other materials. Accumulated moisture made the wall impermeable and weakened the load-bearing material over time. To mitigate moisture effects of 20-28%, it's recommended to use cement-fiberboard (CFB), which can be replaced if damaged without affecting structural integrity. SEM and EDX/EDAX analyses were used to show moisture accumulation at the micro level. It was observed that more oxygen elements were present at the border of the EPS-bead-mortar mix. The fuzzy-based MCDM method helped mitigate uncertainty in parameter selection, while ABAQUS model analysis considered different scenarios with variations in parameters. This research helps developers and practitioners choose materials with low concrete solubility and high concrete vapor diffusion factors for EPS-based panels, reducing moisture damage.

A study on the effect of microspheres on the freeze–thaw resistance of EPS concrete

Abstract This study investigated the influence of microbead dosages (0, 5, 10, 15, and 20%) on the frost resistance of expanded polystyrene (EPS) concrete. Five groups of EPS concrete specimens were prepared and subjected to rapid freeze–thaw tests. The freeze–thaw deterioration of EPS concrete was assessed using macroscopic indicators, including mass loss, strength loss, and dynamic elastic modulus loss. The underlying deterioration mechanism was revealed through the analysis of the EPS particle–matrix interface. A concrete damage plasticity model of EPS concrete based on damage mechanics theory was established. The results indicate that the addition of microbeads increased the strength of EPS concrete by 38–53%, reduced the strength attenuation after freeze–thaw damage by 8.1%, and improved the frost resistance level by 10–60 grades. The optimal dosage of microbeads is 15% of the cementitious material. The interfacial transition zone gaps in EPS concrete with added microbeads after freeze–thaw cycles are smaller, contributing to a more complete hydration reaction. The freeze–thaw damage model established in this study accurately reflects the freeze–thaw damage law of EPS concrete and provides a reference for studying the mechanical properties of EPS concrete under freeze–thaw cycles. The research findings of this study can enhance the strength and service life of EPS concrete, expanding its application scope as a structural material. The study provides valuable insights for future research and engineering applications related to the frost resistance of EPS concrete.

Evaluation of Deformation and Settlement Properties of Cement-Stabilized Silt Mixed with EPS Beads of Various Sizes

The expansion of China’s highways and railways, as well as the growing demand for them, has focused attention on the impact of traffic loads on foundation settling, uneven deformation, and ground cracking. These effects have garnered considerable research attention, with particular emphasis placed on integrating innovative materials into the soil matrix. This investigation involved loading experiments utilizing a combination of lightweight soil, expanded polystyrene (EPS), and cement. Consolidation tests assessed the extent of deformation and settlement, incorporating varying proportions of EPS and cement. The test results show that when subjected to confined conditions, the stress–strain relationship curve assumes a hyperbolic shape closely linked to the e-p curve. This shape effectively captures the unique structural characteristics exhibited by lightweight soils. As the size of the EPS particles and the applied stress increase, a corresponding rise in the strain of the specimens is observed. Simultaneously, as the strain magnitude increases, the elastic modulus experiences a decline. Additionally, it is noted that this trend further increases as the doping of the cement with EPS particles increases. When the EPS volume ratio and cement mix ratio remain constant across different specimens, there is a decrease in structural strength as the size of the EPS increases. In lightweight soil, settlement can occur rapidly, with approximately 95% of total consolidation deformation happening within a few minutes, which suggests that the settlement is instantaneous and primarily consolidation settlement. The structural strength of lightweight soil shows a negative correlation with the size of EPS, implying that larger EPS size may lead to a reduction in strength. Therefore, it is recommended to consistently use EPS beads with a diameter of 3–4 mm during construction.

A simple microplastic splitter for subsampling expanded polystyrene particles

With the high number of microplastic-like particles captured by net hauls including manta or neuston nets, it is often required to subsample in order to decrease sample volume for microplastic enumeration and analysis. Plankton splitter is commonly used to divide microplastic samples. However, current devices such as Folsom plankton splitter and Motoda box splitter have accuracy issues in separating highly buoyant microplastics, namely expanded polystyrene (EPS) as they tend to adhere to the inner walls. Inspired by an apple cutter, we have developed a simple radial splitter made of stainless steel that efficiently divides EPS microplastic samples into precise aliquots. With this simple device, we uniformly divided EPS microplastic samples from marine environments into eight aliquots with no significant differences. The device is a versatile tool to partition all buoyant microplastics including polypropylene and polyethylene microplastics.•The method developed facilitates the precise division of buoyant microplastics into equal aliquots.•The method is specifically effective in splitting expanded polystyrene particles with high buoyancy.

Experimental Study of the Dynamic Characteristics and Microscopic Mechanism of Lightweight Soil Modified with Expanded Polystyrene and Sisal Fibre

With the increasing demand and use of highways, railways and tunnels in China, the phenomena of foundation settlement, uneven deformation and ground cracking caused by the cyclic loading by traffic are becoming increasingly significant. There is now an emphasis on research to prevent or decrease these phenomena by mixing new materials into the soil body. In this study, cyclic loading tests were conducted on lightweight soils modified with expanded polystyrene (EPS) and sisal. A GDS true/dynamic triaxial apparatus was used to study the dynamic elastic modulus and damping ratio of clays with different dosages of EPS and sisal fibre. The modified soil samples were tested, and then, they underwent micro-scale analysis. The results showed that, with the continuous increase in EPS doping and dynamic stress, the trend of the growth of the dynamic strain of the specimens increased. At the same time, with the increase in the dynamic strain, the dynamic elastic modulus decreased, and the trend increased with increasing doping of the soil with EPS particles. A comparison of the improvement effect coefficient of the soil samples showed that the most suitable EPS doping volume was 5%. Different dosages of sisal fibre were added to the most suitable EPS-modified lightweight soil, and the dynamic elastic modulus first increased and then decreased with increasing sisal dosage. In addition, the damping ratio first increased and then decreased. The best dynamic performance of the soil was obtained when the dosage of sisal was 1.2%. Nuclear magnetic resonance and electron microscope scanning tests verified that, when the sisal doping was 1.2%, the soil particles had the largest compactness, the best interparticle bonding and the best improvement effect.

Physical and Mechanical Properties of Expanded Polystyrene (EPS) Particle Lightweight Soil under Freeze-Thaw Cycles.

In seasonally frozen regions, the bearing capacity of soil decreases and gradually deteriorates after undergoing freeze-thaw cycles. To resolve this problem, based on the idea of frost-resistant filling materials, a filling scheme of expanded polystyrene (EPS) particles lightweight soil in cold regions was proposed. Unconfined compressive strength, direct shear, and micro-SEM tests were carried out to study the physical and mechanical properties of EPS particles lightweight soil under freeze-thaw cycles. The results indicate that the EPS particle lightweight soil has good frost resistance and can be used as frost-resistant filling material in cold regions. Under freeze-thaw cycles, EPS particle lightweight soil maintains good integrity; EPS particles can effectively reduce the frost heave rate, mass loss rate, and compressive strength loss rate of lightweight soil. The compressive strength depends on the EPS and cement contents: it decreases with an increase in the EPS content and increases with an increase in the cement content. The strength loss rate decreases with an increase in both. When the content of EPS is larger (more than 2%), the soil cement bound with EPS particles is limited, and the performance of lightweight soil decreases. The shear strength and cohesion decrease with an increase in freeze-thaw cycles and EPS content, and the internal friction angle follows no obvious rule with regard to the increase in freeze-thaw cycles but decreases with an increase in the EPS content. Based on the experimental results, an empirical formula for the compressive strength of EPS particle lightweight soil under freeze-thaw cycles was proposed. This study can provide a reference for the engineering design and application and provide new ideas for resolving freeze-thaw problems in construction engineering in cold regions.

Photoluminescent asphalt coating made from recycled EPS and strontium aluminate particles for improved road safety and waste management: a characterization study using ethyl acetate and acetone diluents

This study focuses on the characterization and evaluation of a photoluminescent asphalt coating made from recycled expanded polystyrene (EPS) and strontium aluminate particles. The aim is to provide an alternative use for the significant volumes of EPS waste present in landfills worldwide. Two diluent mixtures, ethyl acetate and acetone, were used for the degradation of recycled EPS. The objective was to develop a coating that absorbs light emitted by cars at night, thereby enhancing road visibility, particularly in developing countries. The characterization of the coating involved various techniques including photoluminescence spectrophotometry (PL), color analysis, scanning electron microscopy (SEM), x-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), thermogravimetric tests (TGA), as well as tensile and shear tests. The findings indicate that the developed coating is not only technically feasible for solving nighttime lighting challenges but also offers a potential large-scale solution for managing EPS solid waste. The coating has the potential to be used in road demarcation, improving road safety, reducing energy consumption during nighttime, and enhancing the aesthetic appeal of roads by providing artificial lighting without the need for electricity consumption.

Soft polyurethane foam reinforced by expanded polystyrene particles: Compression performance, strain rate, and cyclic compression response

AbstractThe incorporation of particles with soft polyurethane (PU) foam aims to mechanically strengthen the PU foam as PU foam falls short of the mechanical expectation of academia and industries. In this study, the expanded polystyrene (EPS) particles are added to soft polyurethane foam, and composite foam with higher mechanical properties is successfully prepared by one‐step foaming process. The results show that under optimal conditions that is, EPS particle size of 0.5 mm and content of 2.5 wt% (EPS‐0.5‐2.5%), the synthesized foam has the smallest bubble pore diameter of 80 μm and has a stress of 0.284 MPa at 75% strain, which is much higher than that of blank polyurethane foam. As a result of a rise in the quantity of EPS particles, the composite PU foam shows a lower dependency on the strain rate. After the multiple cyclic compression test, PU foam exhibits a descending trend on the stress in the deformation plateau region. Besides, the low‐velocity impact test results indicate that the peak contact force of EPS‐0.5‐2.5% is lower than that of the control group by 632 N.

Using Image Texture Analysis to Evaluate Soil–Compost Mechanical Mixing in Organic Farms

Soil amendments (e.g., compost) require uniform incorporation in the soil profile to benefit plants. However, machines may not mix them uniformly throughout the upper soil layer commonly explored by plant roots. The study focuses on using image texture analysis to determine the level of mixing uniformity in the soil following the passage of two kinds of harrows. A 12.3-megapixel DX-format digital camera acquired images of soil/expanded polystyrene (in the laboratory) and soil/compost mixtures (in field conditions). In the laboratory, pictures captured the soil before and during the simulated progressive mixing of expanded polystyrene particles. In field conditions, images captured the exposed superficial horizons of compost-amended soil after the passage of a combined spike-tooth–disc harrow and a disc harrow. Image texture analysis based on the gray-level co-occurrence matrix calculated the sums of dissimilarity, contrast, entropy, and uniformity metrics. In the laboratory conditions, the progressive mixing resulted in increased image dissimilarity (from 1.15 ± 0.74 × 106 to 1.65 ± 0.52 × 106) and contrast values (from 2.69 ± 2.06 × 106 to 5.67 ± × 1.93 106), almost constant entropy (3.50 ± 0.25 × 106), and decreased image uniformity (from 6.65 ± 0.31 × 105 to 4.49 ± 1.36 × 105). Using a tooth-disc harrow in the open field resulted in higher dissimilarity, contrast, entropy (+73.3%, +62.8%, +16.3%), and lower image uniformity (−50.6%) than the disc harrow, suggesting enhanced mixing in the superficial layer.

Dynamic behavior of EPS amended lightweight soil under cyclic loading

The dynamic behavior of expanded polystyrene (EPS) particle amended lightweight soil was explored using consolidated undrained dynamic and monotonic triaxial tests conducted on samples of lightweight soil with different mixing ratios. The dynamic stress, dynamic strain, and dynamic pore pressure time history curves, and shear strength criterion were studied. As a kind of structural soil, the dynamic strain time history curves of lightweight soil could be divided into three stages as the vibration compaction, vibration deformation and vibration failure stages according to the cumulative deformation rate of dynamic strain, but the vibration compaction stage was not obvious. The dynamic strain accumulation for lightweight soil was mainly single amplitude in compressive region. The deformation rate during the vibration failure stage for the lightweight soil was larger than that of the remolded soil owing to its increased stiffness and brittleness with added cementation. Unlike that of the remolded soil, dynamic pore pressures fluctuated markedly in lightweight soil tests. The dynamic pore pressure development of lightweight soil was found to relate to the mixing ratios of its components and the confining pressures. For lightweight soil samples with high EPS particle mixing ratio, the dynamic pore pressures remained in the positive range, increasing unsteadily with some fluctuation. However, for lower EPS content samples in different confining pressures, the dynamic pore pressure showed decreasing trends into the negative range, again changing unsteadily with fluctuation, showing a trend of suction and soil skeletal dilation. Based on analysis of results, it was determined that, general pore pressure, limit equilibrium and yield criterias were not suitable to describe the dynamic behavior of lightweight soil, while the dynamic strain criterion was suitable. Excluding the plastic deformation range, the single amplitude dynamic compression strain of 5% was recommended as the dynamic strain criterion to determine dynamic strength of lightweight soil.

Gypsum Composites with Modified Waste Expanded Polystyrene

The construction and demolition waste recycling into secondary raw materials is vital to achieving a sustainable and circular building life cycle. Expanded polystyrene (EPS) is one of the materials whose recycling rate should be increased. EPS boards can be shredded and used as aggregate of lightweight cement composites resulting in a material with combined properties subjected from EPS and mineral binder. To reduce the open structure of shredded EPS particles, proper treatment could improve EPS performance. The heat treatment of the aggregates can reduce the volume and increase their density. In this paper, EPS aggregates were heat-treated at 120 and 130 °C, and heat-modified EPS aggregates with a bulk density of 40 and 100 kg/m3 were incorporated as filler material in gypsum composites. The composites’ density, compressive strength, thermal conductivity, and sound absorption were characterized. Results indicate that a composite with a compressive strength from 15 to 136 kPa and a material density ranging from 48 to 194 kg/m3 can be obtained. Thermal conductivity was achieved from 0.0390 to 0.0604 W/(mK). Following the ISO 10534-2 standard, the noise reduction coefficient was determined and showed promising results at 600 to 800 Hz, reaching a sound absorption coefficient of 0.88.

Effect of foam stabilization on the properties of foamed concrete modified by expanded polystyrene

This paper aims to study the modified foamed concrete by mixing expanded polystyrene (EPS) particles. In order to analyze the influence of EPS particle dosage and particle size on the mechanical properties and thermal conductivity of the foamed concrete, the EPS modified foamed concrete was compared with the ordinary foamed concrete. The pore structures of the foamed concrete with and without EPS were characterized and compared by scanning electronic microscopy (SEM), mercury intrusion porosimetry (MIP), and image-pro plus (IPP). The results showed that when large and small size EPS replaced 60% foam, the water absorption of the EPS modified foamed concrete was approximately 38% and 55% lower than that of the ordinary foamed concrete, respectively, with a corresponding 0.13 and 0.5 MPa increase in compressive strength. In addition, the thermal conductivity of the EPS modified foamed concrete was similar to/even slightly lower than that of the ordinary foamed concrete. The addition of EPS in foamed concrete increased the proportion of small connected pores and reduced the proportion of medium and large pores. Overall, the addition of EPS in foamed concrete can effectively improve the stability.

Multiscale Enhancement Mechanisms of EVA on EPS-Cement Composites

Ethylene-vinyl acetate (EVA) lotion can significantly improve the interface problems caused by the physical and chemical differences between expanded polystyrene (EPS) beads and cement, which is one of the reasons why EPS cement composites are widely used in the construction field. However, the research on its problems is often limited to phenomenological engineering methods, ignoring the potential interaction mechanism in atomic structure. Therefore, in this study, the strengthening mechanism of EVA on EPS particle–cement slurry interface was systematically studied from the aspects of macromechanical properties, microstructure characteristics, chemical composition, and molecular structure. In terms of physical test, it was found that the compressive strength and flexural strength of EPS-cement-based materials containing EVA are increased by 19% and 31%, respectively, at 28 days when the content of EPS particles is the same. It was observed through an electron microscope snapshot that EVA makes a uniform and dense interface structure between EPS particles and cement. For chemical tests, EPS particle surface hardening cement was ground into powder and tested by X-ray diffraction and Fourier transform infrared spectrometer. It was comprehensively analyzed that EVA reduced the hydration product Ca(OH)2 and increased calcium silicate hydrate (C-S-H) at the interface. In terms of numerical simulation, through molecular simulation modeling and calculation, it was found that the introduction of EVA can produce more stable hydrogen and ion bonds at the EPS–C-S-H interface, which plays a vital role in reducing the interface effect and increasing the interface binding energy.

Study on Dynamic Modulus and Damping Characteristics of Modified Expanded Polystyrene Lightweight Soil under Cyclic Load.

In recent years, expanded polystyrene (EPS) lightweight soil has been widely used as subgrade in soft soil areas because of its light weight and environmental protection. This study aimed to investigate the dynamic characteristics of sodium silicate modified lime and fly ash treated EPS lightweight soil (SLS) under cyclic loading. The effects of EPS particles on the dynamic elastic modulus (Ed) and damping ratio (λ) of SLS were determined through dynamic triaxial tests at various confining pressures (σ3), amplitudes, and cycle times. Mathematical models of the Ed of the SLS, cycle times, and σ3 were established. The results revealed that the EPS particle content played a decisive role in the Ed and λ of the SLS. The Ed of the SLS decreased with an increase in the EPS particle content (EC). The Ed decreased by 60% in the 1-1.5% range of the EC. The existing forms of lime fly ash soil and EPS particles in the SLS changed from parallel to series. With an increase in σ3 and amplitude, the Ed of the SLS gradually decreased, the λ generally decreased, and the λ variation range was within 0.5%. With an increase in the number of cycles, the Ed of the SLS decreased. The Ed value and the number of cycles satisfied the power function relationship. Additionally, it can be found from the test results that 0.5% to 1% was the best EPS content for SLS in this work. In addition, the dynamic elastic modulus prediction model established in this study can better describe the varying trend of the dynamic elastic modulus of SLS under different σ3 values and load cycles, thereby providing a theoretical reference for the application of SLS in practical road engineering.

Characteristics of dynamic shear modulus and damping ratio and the structural formula of EPS particles lightweight soil

Dynamic triaxial tests of lightweight soil were conducted to explore the dynamic characteristics of expanded polystyrene (EPS) particle lightweight soil under traffic load. The effects of different mixed ratios, confining pressure, frequency on the backbone curves, dynamic shear modulus, and damping ratio characteristics of lightweight soil were investigated. The maximum dynamic shear modulus formula and maximum damping ratio formula of lightweight soil were established. The results indicated that backbone curves of lightweight soil had typical nonlinear and strain-hardening characteristics. With an increase in dynamic shear strain, the dynamic shear modulus curves appeared as inverse “S-shaped”. The dynamic shear modulus in the initial stage varied under different confining pressures. For γd＞10−4, the attenuation rate of the dynamic shear modulus increased with an increase in the dynamic shear strain, and for γd＞10−2, the relationship curve between the dynamic shear modulus and dynamic shear strain coincided gradually, and the attenuation process then stabilized. Owing to the special structure of lightweight soil, the damping ratio curves were “Bell-shaped” and “S-shaped.” Both the confining pressure and compressive yield stress determined the change trends of the damping ratio curves of the lightweight soil. The specimens were in an over-consolidated state and the mixed soil was in the state of shear dilatancy under dynamic loads when the confining pressure was less than the compressive yield stress, resulting in “Bell-shaped” damping ratio curve. The specimens were in the normal consolidated state and the mixed soil was in the state of shear shrinkage under dynamic loads when the confining pressure was greater than the compressive yield stress, resulting in “S-shaped” damping ratio curves. The calculation methods of the relative structural degree k and generalized void ratio e' of lightweight soil were defined to express the structural damage laws of lightweight soil having different mixed ratios under complex stress conditions using a unified formula. Based on Hardin's empirical formulas, the maximum dynamic shear modulus and maximum damping ratio formulas of lightweight soil were established by introducing the relative structural degree k and generalized void ratio e'. The formulas can quantitatively describe the dynamic responses of the special structure of lightweight soil under complex stress conditions.

Homogenization approach for estimating the effective thermal conductivity of Lightweight Expanded Polystyrol Concrete

This paper aims to determine the macroscopic thermal conductivity coefficient of Lightweight Expanded Polystyrene Concrete (LEPS-C) using the homogenization approach through analytical calculations. The influence of expanded polystyrene on the overall thermal conductivity coefficient of LEPS-C was determined using classical homogenization models based on the solution of the Eshelby problem, with the matrix phase being concrete and the inclusion phase being expanded polystyrene particles randomly distributed in the matrix phase. The content of substituted expanded polystyrene particles was varied from 0% to 40% by volume of concrete. The analytical calculation results obtained from the homogenization models were compared with the experimental results, showing good agreement and demonstrating the efficacy of the homogenization method in predicting the macroscopic thermal conductivity of LEPS-C.

Experimental study on levitation control of particles and liquid droplets by vortex acoustic field enhanced by subwavelength pipe

The nonlinear propagation of acoustic waves in a medium generates acoustic radiation force. Using acoustic radiation force, particles and liquid droplets in gases can be levitated and manipulated. Acoustic levitation techniques can manipulate larger objects in the medium without contact, and therefore have been widely used in chemical analysis, droplet dynamics, and bioreactors. The acoustic levitation researches mainly focus on manipulating particles and droplets in an open environment, which provides flexibility in its use. However, this approach has limitations in terms of its efficiency in utilizing acoustic field energy. In this work we propose a concept of subwavelength pipe-enhanced acoustic tweezers, in which the acoustic field is used to manipulate expanded polystyrene particles (EPS) and droplets inside an acoustic pipe with an inner diameter smaller than the wavelength. In this work, we use four small transducers to excite a single low-order mode of a circular waveguide and its simplex state, and we also use the vortex sound field generated inside the waveguide to levitate and manipulate expanded polystyrene particle and droplet in the air. Compared with previous work in an open environment, we significantly enhance the acoustic radiation force by means of the acoustic resonance effect of the subwavelength duct, with both radial and axial suspension force magnitude increasing considerably. Similar concepts of subwavelength optical waveguides and resonant cavities and their effectiveness were already well known and widely used in the field of optics. In this work we first explain theoretically the basis for the design of subwavelength pipe-enhanced acoustic tweezer dimensions. Then, we point out in simulation that the pipe-enhanced acoustic tweezers, compared with the open environment acoustic tweezers, have strong sound field gradient distribution and acoustic radiation force distribution in the pipe. This conclusion is demonstrated experimentally. Finally, the manipulation of droplet and particle levitation and rotation in subwavelength-pipe-enhanced acoustic tweezers is systematically carried out. In this work we introduce the concept of subwavelength acoustic pipe for acoustic manipulation, which is expected to deepen the physical understanding of the interaction between acoustic fields and matter, and to develop new miniaturized acoustic manipulation devices for levitating particles and droplets.