Expanded Polystyrene Density Research Articles

Axial compression testing and constitutive model of a novel BF-reinforced ambient-cured LEGC

Ambient-cured lightweight expanded polystyrene geopolymer concrete (LEGC) currently undergoes early shrinkage cracking, and the low density of EPS causes segregation during the mixing process, resulting in a significant decrease in the strength of LEGC. To solve the above problems to obtain higher strength LEGC and promote its wide application, uniaxial compression tests and constitutive modeling studies of LEGC with different basalt fiber (BF) lengths (3 mm, 6 mm, 9 mm, 12 mm and 15 mm) reinforced with different expanded polystyrene (EPS) volume contents (10%, 20%, 30% and 40%) were conducted in this study. First, the damage pattern of the specimen was analyzed, and the crack development morphology was analyzed based on the Digital Image Correlation-3D (DIC-3D) technique. Additionally, the mechanism of BF-reinforced of LEGC was analyzed comprehensively at three levels: micromechanical theory, microscopic (scanning electron microscopy, SEM) and mesoscale (computerized tomography, CT). Empirical formulas for peak stress, peak strain, threshold stress, threshold strain and elastic modulus were established based on the stress‒strain curves of the specimens. In addition, the specific form of the damage evolution equation considering the energy dissipation of the specimen was derived from the energy balance principle and basic laws of irreversible thermodynamics based on composite damage theory. Finally, elastic‒plastic damage constitutive models established previously and in this study were compared, and the results showed that the method proposed in this study can better reflect the damage evolution of BF- reinforced LEGC.

Use of expanded polystyrene (EPS) as a support media for trickling filters applied to wastewater treatment

Developing countries demand a sewage treatment plant with low-cost processes that are viable in warm climates. The UASB (upflow anaerobic sludge blanket) associated with the trickling filter (TF) would meet this requirement. However, there is still a need for studies aimed at the use of new support media. Based on this, the use of expanded polystyrene (EPS) as a support media in TF was evaluated in this study. As a result, the TF filled with EPS presented a final effluent with quality similar to reactors filled with crushed stone or patented materials. The density of EPS (6.56 ± 0.30 kg m−3), the void ratio (61.7 ± 2.1%), and the mean surface area (201.9 ± 14.9 m2 m−3) once again demonstrate that EPS has characteristics similar to other alternative or patented materials. Therefore, we found that EPS can be another alternative material to be used in sewage treatment, and also that one could give an appropriate destination to a portion of this material, which is currently still discarded in landfills.

Creep Simulation and Validation for a Finite Element Analysis of Expanded Polystyrene-Based Cushioning Systems

The creep strain resistance of expanded polystyrene (EPS) is important; thus, time-dependent creep properties of EPS have been of significant interest. This study is a part of the computer-aided engineering (CAE) prediction-technology development for the inclination of unitized loads of packaged appliances applied to EPS-based cushioning systems. Creep properties are validated to ensure finite element analysis (FEA) reliability regarding the creep behavior of EPS-based cushioning systems. The elastic modulus and Poisson’s ratio (EPS elastic properties) as well as creep properties (plastic properties) were measured. The EPS density range was 16–30 kg/m3, and the temperature range was 0–60 °C. Because the measured mechanical properties were not temperature-dependent, only their density dependence was analyzed. The EPS behavior, measured over 12 h, exhibited a significant creep amount and rate, depending on the applied stress level. FEA was performed on 7-day-long EPS creep, using the measured EPS elastic and plastic properties. The FEA and experimental results were strongly concordant. These EPS creep validation results are expected to improve the reliability of FEA for creep behavior studies of EPS-based cushioning systems.

Ultrasonic characterization of expanded polystyrene used for shallow tunnels under seismic excitation

Expanded Polystyrene (EPS) is used as an inclusion to mitigate stresses acting on tunnels. In this study, the efficiency of utilizing EPS in reducing dynamic loads acting on shallow tunnels was studied. To gauge this, dynamic modulus of elasticity ( E d ) and shear modulus ( G ) of EPS with densities equal to 25, 30, and 35 kg/m 3 were characterized based on series of ultrasonic tests, where E d ranged from 3500 to 6578 kPa, and G ranged from 1535 to 2741 kPa. A correlation was developed between EPS density and damping coefficient, which ranged from 1% to 2.3% based on G and the ultrasonic wave decay. A model was developed for a cut-and-cover tunnel with EPS along its side walls, and a parametric study was conducted using EPS thickness to tunnel depth ratio (t x /h 1 ) varying from 0.05 to 0.20. At tunnel critical sections, normal and bending were reduced by 30% and 46%, respectively.

Experimental and numerical investigation of expanded polystyrene (EPS) geofoam samples under monotonic loading

The recent increase in the use of Expanded Polystyrene (EPS) geofoam in construction and geotechnical projects has driven researchers to investigate its behavior, more deeply. In this paper, a series of experimental tests to investigate the stress-strain behavior and the mechanical properties of EPS blocks, under monotonic axial loading are presented. Four different densities of cylindrically shaped EPS with different dimensions are used to investigate the effects of loading rate, height and diameter, as well as the influence of the density of EPS on the stress-strain response. The results show that increasing the height of the EPS samples leads to instability of the sample and consequent lower resistance to the applied pressure. Large EPS samples show higher Young’s modulus and compressive resistance due to some boundary effects. An increase in the rate of loading can increase the elastic moduli and compressive resistance of the EPS geofoam samples, which also varies depending on the density of the samples. It was also determined that the elastic modulus of EPS increases with increasing EPS density. By implementing an efficient numerical procedure, the stress-strain response of EPS geofoam samples can be reproduced with great accuracy. The numerical analysis based on the proposed method can used to evaluate the effect of different factors on the behavior of EPS geofoam

Structural Use of Expanded Polystyrene Concrete

Expanded polystyrene (EPS) wastes are generated from industries and post-consumer products. They are non-biodegradable but are usually disposed by burning or landfilling leading to environmental pollution. The possibility of using EPS as partial replacement for fine aggregates in concrete has generated research interests in recent times. However, since the physical and mechanical properties of EPS are not like those of conventional fine aggregates, this study is focussed on the use of EPS as an additive in concrete while keeping other composition (sand and granite) constant. Expanded polystyrene was milled, the bulk density of EPS was 10.57kg/m3 and particle size distributions were determined. Engineering properties of expanded polystyrene concrete were determined in accordance with BS 8110-2:1985. The result showed that the amount of expanded polystyrene incorporated in concrete influence the properties of hardened and fresh concrete. The compressive strengths of 17.07MPa with 5 % expanded polystyrene concrete at 28 days for example can be used as a lightweight concrete for partitioning in offices. Incorporating expanded polystyrene granules in a concrete matrix can produce lightweight polystyrene aggregate concrete of various densities, compressive strengths, flexural strengths and tensile strengths. In conclusion, this reduces environmental pollution, reduction in valuable landfill space and also for sustainability in construction companies

Density Variation in the Expanded Polystyrene Foam of Bicycle Helmets and Its Influence on Impact Performance.

Bicycle helmets attenuate head impacts using expanded polystyrene (EPS) foam liners. The EPS density plays a key role in determining the helmet and head response during an impact. Prior pilot work in our lab showed that EPS density varied by up to 18 kg/m3 within a single helmet, and thus the purpose of this study was to quantify the regional density variations within and between helmets and to establish how these variations influence helmet impact performance. We evaluated 10-12 samples of two traditional and two bicycle motocross (BMX) bicycle helmets with EPS liners. The bulk liner density and density of 16-19 cores extracted from specific locations on each sample were measured. Additional samples of two of these helmet models were then impacted at 3.0, 6.3, and 7.8 m/s to determine the relationship between local EPS density and helmet impact performance. We found that density varied significantly within each sample in all helmet models and also varied significantly between samples in three helmet models. The density variations were not symmetric across the midline in two of the four helmet models. The observed density variations influenced the helmets' impact performance. Our data suggest that variations in peak headform acceleration during impacts to the same location on different samples of the same helmet model can be partially explained by density differences between helmet samples. These density variations and resulting impact performance differences may play a role in a helmet's ability to mitigate head injury.

Electrospun nanofiber from various source of expanded polystyrene (EPS) waste and their characterization as potential air filter media

This paper reported on the fabrication of nanofibrous membranes from various sources of expanded polystyrene (EPS) waste using electrospinning technique and their application as air filter media. The filter membranes were made from four EPS waste sources, i.e. food packaging, EPS craft, instant noodle cup, and electronic packaging. The properties of the membranes fabricated from those sources were compared to obtain the best EPS waste source for air filter application. To make the precursor solutions, those samples were dissolved in d-limonene:DMF with the concentration of 15, 20, and 25 wt%. The solid EPS density, solution viscosity, and surface tension were measured. The fiber diameter and morphology of nanofibers were characterized by scanning electron microscopy (SEM) for each EPS variation. The fabricated membrane properties (crystallinity, wettability, and mechanical strength) and filtration properties (pressure drop, PM2.5 filtration efficiency, and quality factor) were fully characterized and analyzed. Homogeneous fiber diameter with various morphologies (beaded, wrinkled, and smooth fiber) were obtained from all samples with hydrophobic to super-hydrophobic surface (water contact angle ranging from 106 to 153°). Also, the EPS solid density affected the solution viscosity with the expression of η = 0.132 ρ0.29, which then affected the fabricated membrane packing density, porosity, and mechanical properties. Overall, the experimental results showed that all EPS nanofiber filters had great potential as an air filter media. The EPS filter made from food packaging waste with the solution concentration of 15 wt% exhibited the highest efficiency and quality factor of 99.99% and 0.15 Pa−1, respectively.

Experimental Investigation on the Swelling Behavior of Expansive Soils with EPS Geofoam Inclusion

Swelling pressure of expansive soils can impose significant threat to the infrastructure built on them. Placing of compressible inclusion material, such as expanded polystyrene (EPS) geofoam, in expansive soils can effectively reduce the swelling pressure acting on the structure. This paper describes the experimental design, results of the tests used to investigate the use of compressible EPS in the form of geofoam layer (GL), geofoam column (GC) inclusion to reduce the swell potential, and swelling pressure of expansive soils. The tests were carried out on large one-dimensional consolidation equipment which can accommodate the California bearing ratio mold. Two different EPS geofoam densities were tested on two types of soil with varying swell potential under swell–compression test. The results of the tests are compared for the soil samples with and without GL and GC inclusion. The test results demonstrate that the percentage reduction in swell and swelling pressure is increased with increasing the thickness and cross-sectional area of GL and GC inclusion in expansive soils. In addition, the optimal EPS density was determined with respect to the maximum reduction in swelling.

Behavior of expanded polystyrene (EPS) blocks under cyclic pavement foundation loading

This study introduces a mechanism for initial assessment and future development to improve understanding of expanded polystyrene (EPS) behavior as a super-lightweight material for road construction. Large scale cyclic plate load tests on model pavements were performed. The effect of several factors including thickness of soil, thickness of subsequent EPS layers and density of EPS on the surface deformations, resilient modulus (Mr) and interlayer pressure transfer were investigated. The results indicated that, compared to a covering soil layer of 300 mm, the rut depth on the loading surface reduced by 13.5% and 40.8% when the soil thickness was increased by 33% and 100%, respectively. With a constant soil thickness, increasing the thickness of an upper (denser) EPS layer with respect to a bottom (softer) EPS layer, from 200 mm to 600 mm, would only result in a 20% decrease in the peak settlements after loading. Resilient modulus of the system was found to be dependent on soil thickness. A designer can choose an appropriate resilient modulus assuming the soil-EPS composite acts as subgrade or subbase. In order to extend the results to a wider range of geofoams, soils and layer thicknesses, a simple stress analysis method was also trialed.

Micro- and macro-mechanical study of compressive behavior of expanded polystyrene geofoam

ABSTRACT: A series of uniaxial and triaxial compression tests was carried out in order to study micro- and macro-mechanical compressive behavior as well as some other mechanical properties of expanded polystyrene. Micromechanical behavior was analyzed by performing uniaxial compression tests on small cubic specimens. These tests were carried out using a load frame designed to be placed inside a scanning electron microscope. Using an automatic camera, micrographic sequences were taken during the loading process. These photographic sequences allowed the identification of the internal structure changes that occurred at different strain levels. Macro-mechanical behavior of expanded polystyrene (EPS) under compressive loading was investigated by means of triaxial tests on 10 cm-diameter specimens. Triaxial test results showed that the behavior was strongly influenced by EPS density, confining stress and displacement rate. Finally, based on the triaxial test results, a set of equations was proposed to estimate the compressive behavior of EPS and the accuracy of the equations was assessed by comparisons with experimental results.

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.

Deformability of expanded polystyrene under short-term compression

The results obtained in an experimental investigation of deformability of expanded polystyrene (EPS) under short-term compression are presented. The density of EPS varied from 13 to 28 kg/m3. The method of design of experiments was used to determine the elastic modulus and the ultimate strain (corresponding to the end of quasi-linear deformability) under compression stresses operating perpendicularly and parallel to the faces of EPS products. A graphical interpretation of the models is also presented. Based on the experimental data obtained, it was concluded that the expanded polystyrene was homogeneous in mutually perpendicular planes with respect to its deformability in compression.

Deformability and strengh of expanded polystyrene (EPS) under short-term shear loading

Data obtained in investigating the ultimate strength and deformability of expanded polystyrene under short-term shear loading according to EN 12090 are discussed. Linear regression equations are used for describing the ultimate shear strength and modulus in relation to the density of EPS. A correlation is found to exist between the ultimate strength of EPS and its density and specimen thickness. An empirical dependence between the shear modulus and density of EPS is established. The strains corresponding to the conditional limit of proportionality and to the ultimate shear strength of EPS in short-term loading are determined.

Stress–strain modeling of EPS geofoam for large-strain applications

Both small- and large-strain applications of expanded polystyrene (EPS) geofoam involve interactions with the surrounding geologic materials. The stress–deformation response of this material, however, differs significantly from those of the adjoining geologic materials. A well-justified constitutive law for EPS is, thus, a prerequisite for reliable solutions for soil-structure interaction problems where such material is used. This paper describes a stress–strain law for EPS geofoam for its large-strain applications based on the incremental theory of plasticity. In the derivation of the constitutive relationship, the geofoam was taken as a von Mises material, and it was assumed that the hardening regime follows a hyperbolic curve. The material parameters of the constitutive model were determined from a series of unconfined compression tests performed on EPS specimens of various sizes, shapes and densities. These parameters are functions of the absolute dimensions of the tested specimens as well as the density of EPS. The validity of the model was confirmed by numerical simulations on the compression testing program of EPS geofoam.

Analysis of the Viscoelastoplastic Behavior of Expanded Polystyrene under Compressive Loading: Experiments and Modeling

The use of expanded polystyrene (EPS) in road paving where the soil exhibits special properties (for example, compressive soil) calls for the necessity of investigating the mechanical behavior of this material. In this work, a study of the EPS compressive behavior is presented. It is divided into two parts: experimental and modeling investigations. The experimental results show that the EPS global compression behavior is characterized by three stages. Analysis of the results shows that the density of EPS plays an important role. A phenomenological mechanical model is considered in order to simulate the EPS viscoelastoplastic behavior in the case of compressive loading. A numerical analysis has been made in order to describe the mechanical behavior of the EPS material. This investigation has revealed a good correlation with the experimental results.