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Manufacturing Quality Investigation of EPS Block with Homogeous Test

Lee-kuo Lin 1

Associate Professor

Civil Engineering Department

National Taipei University of

Technology

Taipei City ,Taiwan, R.O.C.

Kenji Sasaki 2

Manager of

Overseas Marketing Project Team

SEKISUI PLASTICS CO,. LTD.

Tokyo City , Japan.

Shang-Juin Chiou3

Graduate Student

Civil Engineering Department

National Taipei University of

Technology

Taipei City ,Taiwan, R.O.C.

ABSTRACT

EPS light-weight embankment method is a kind of construction method which is used

pieces of EPS blocks to stack up as a sequence of geofoam embankment. EPS block is made

from styrene particles through the process of foaming, pressuring and heating. If quality of EPS

block production is not good enough, it will make the EPS block damage due to un-uniform

deformation. Therefore, if using poor quality of EPS blocks as the road sub-grade embankment,

it will have a serious problem. This study focuses on EPS block productions of Taiwan and Japan

to do uniformity analysis and comparison. Because Japan has considerable experience in EPS

technology, so in this study, Japanese EPS block would be the comparison object to understand

the difference of the quality EPS manufacturing between Taiwan and Japan.

The study transmits two 20kgf/m3 (20K) EPS blocks with dimension of 2m1m0.5m from Japan to Taiwan, then makes homogenous test of these two samples. The same testing

process is made for Taiwanes EPS samples. After comparison and analysis of the measured data,

uniformity quality of EPS productions are feedbacked to those Japanese and Taiwanes

manufacture firms.

KeywordEPS, geofoam, manufacturing, homogeous, uniformity test

I. PREFACE

Taiwan has a harsh natural environment and high population in a slender area. In recently

years, economics of urban area are rised up, civilizans move to develop the suburban or

mountain area. Meanwhile, Taiwan is located at the Circum-Pacific seismic zone and

sub-tropical humid climate of special geographical place, such situation casued that Taiwan is a

country with frequent earthquakes in the world [1]. Due to high annual rainfall, it arouses

landslide or debris-flow frequently happened. After the 921 Gigi earthquake which was

happened in 1999, mountains of Taiwan generally have potential hazard of sliding and falling

rocks to launch the debris flow disaster. Due to the mount of natural disasters, it makes Taiwan

urgently needed to develop better disaster prevention system than other countries.

EPS is the generic abbreviation of Expandable Poly-Styrolene, its refining liquid-mononer styrene from petroleum, re-synthesis to solid polystyrene, after mixed vesicant in accordance

with the pressure tube to cylinder pressure and temperature, put foaming material into casting

mold pressurize and heating to the melting point to make the EPS block [2, 3]. Because there are

lots of characteristics with EPS, such as light weight, impact absorbon, self-supporting, water

resistance, insulation, easy construction and other features [1, 4], EPS is also called the geofoam

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due to it is often used to replace the embankment material in civil engineering (Figure 1).

Figure 1. EPS embackment in Taiwan

EPS light-weight embankment method is one kind of construction method which is used by

pieces of EPS blocks to stack up as a sequence of embankment. If quality of EPS block

production is not qualified, there will be problems of unhomogeous foam particles and will make

the EPS block in the pressure generated to damage (Figure 2). This study focuses on EPS blocks

manufacturing production in Taiwan and Japan to do uniformity analysis and comparison, then

feedbacks the experimental result to EPS suppliers. Because there has considerable experience of

EPS technology in Japan, two 20 kgf/m3 EPS blocks supplied from the Sekisui Plastics

Company will be used as the compared object of this study. It is looking forward to the result of

this research that can promote the quality of EPS manufacturing and disaster prevention in the

domestic construction industry and engineering applications.

Figure 2. Road damaged due to poor EPS quality

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II. EPS MAUNFACTURING PROCESS

Polymer plastic raw materials are extracted from crude oil distillation and oil/gas

separation process mainly. EPS is one of its derivatives. The refining process produces 96% of

products are supplied to non-oil fuel vehicles and machines. The plastics material derived from

the refining process accounts for about 4% of products, and EPS products accounts for only

0.1% (Figure 3). In Taiwan, ablock of EPS is made from particles of polystyrene (PS) being

expanded and melted in an automatic mold by adding steam. Expanded polystyrene is created

during a two-stage process. In the first stage, expandable polystyrene resin is pre-expanded by

a hydrocarbon-blowing agent that is contained within tiny resin beads. When the beads are

exposed to steam, the polymer softens and the blowing agent expands, creating a cellular

structure within the "pre-puff" beads (Figure 4)[5]. After a short stabilization period, the pre-puff

is placed in a large rectangular block mold and steam is injected into the mold. Under such heat

and pressure, the beads further expand and use to form a molded block [3](Figure 5). The result

is a white, synthetic material that has a texture of closed, gas filled cells. Individual cells, or

beads, are still visible after the molding process, but the beads have coalesced, to form a closed

fabric, with essentially no void between the cells [2](Figure 6). The process can be done by an

EPS manufacturer. There are 18 EPS manufacturers in Taiwan. In this research 8 of those EPS

manufacturers were visited, then the complete manufacturing process were derived as shown in

Figure 7.

Distillation

FuelsOther

Derivatives

Hydrocarbon

Separation

Ethanes Diesel fuel

Fuel oils Jet fuel

Gasoline Kerosene

Liquid Petroleum gas

Natural gas

Alkenes Lubricants

Wax Paraffin wax

Sulfuric acid Bulk tar

Asphalt Petroleum

Sulfur or Coke

Generally used in transportation,

power

plants and heating. Normally results

in

the destruction of the material while

generating energy.

Over 4000 products, compounds

through polymerisation processes,

motor oils and greases, acids and

further derivatives

Crude

oil

Plastics

4%

EPS

01%

Others

96%

Figure 3. Crude oil refining process and product [6]

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(a) Beads of PS and EPS

(b) Optical microscope picture of EPS pre-puff

beads

Figure 4. Pictures of PS and EPS Beads

Poly-

Styrene

Raw

Material

First Amatured and

Dried

First Expanded

EPS Block

Mold ProduingSecond Amatured and

Dried

Second Expanded

Figure 5. EPS expended process [6]

Figure 6. Optical microscope picture of EPS

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Figure 7. The flow chart of EPS manufacture

In Japan, the first step of EPS production process is to foam the PS particle once, foaming

rate is 5 times to 100 times, then placed at the silo for one day. After that, feeded into molding

machine to foam EPS block by high temperature and high pressure extrusion [7]. The

manufacturing process is shown in Figure 8. After EPS block shaping printed EPS block on

number and date and put into dry room for 7 days. Then measured weight and size, randomly

sampling of 1 / 100 individuals after cutting proceed compression strength tests and fire test,

confirm the quality of blocks will be kept to a shipping warehouse. Japanese EPS blocks have

been recognized quality standard by EPS development institutions. Figure 9 is for the Japanese

engineering backfill with EPS, the EPS block have been marked exclusive sign.

Vacuum

cooling

Water

cooling

Exhaust

Two sides

heating

Behind sides

heating

Heating

Mold

heating

bloeback

Close mold,

foam

Eject

Separated from

the mold

Close mold, Filled with air

Filling tube or Machine residual foam particles back into

the hopper

pressurized air, so that products from the mold

release

Making water to evaporate, the foam pressure drop

down

Make mold cooling

Pressure release

Promote the product surface extension

Through the steam to promote the integration of

secondary foam

Steam pipe to remove water in the mold and raise

the temperature

Using EJECT PIN to remove products after

extrusion

Figure 8. EPS block manufacturing flow

chart in Japan

Figure 9. Japanese quality certification of

EPS block

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The material characteristics of EPS are including the following[5, 7, 8]:

(1) Lightweight: the density of EPS is only 1/100 of sand, it is enough to support soft

domain foundation.

(2) Economical: short duration, space saving, less excavation, low maintance and lower

total cost.

(3) Easily for construction: large machines do not needed only manpower is required.

(4) Self-supporting: low Poisson ratio, high self-supporting can reduce lateral soil pressure,

suitable for use in construction of retaining backfill material.

(5) Excellent impact absorption: EPS with less impact and shock effect.

(6) Water resistance: foaming material is hard to absorb water and not easy to distort.

The material characteristics of EPS can be used in many ways of engineering applications

and it can become substitute to instead of sand for the backfill material [9].

III. HOMOGEOUS TEST of EPS BLOCKS

The concept of EPS homogenous test is launched from the first author in 2010 [5]. For

the testing process, the first step is to cut the EPS block into cube of 10cm10cm10cm then

tag number on cube specimens. In this research, the main experiment divides into uniformity test

of EPS specimens, physical properties test and impacting test. Physical properties test include the

compressive strength, water absorption and hardness. The main purpose of the experiment is to

compare quality of EPS production between Taiwan and Japan, then provides Taiwans EPS

manufacturers to improve quality control of their processes in advanced. In this research, the

testing process is shown in Figure 10.

Experimental

planning

Data verification and

analysis

Water

absorption

Physical properties

test

Homogeous

property test

Hardness testCompression

test

Cutting block

Figure 10. Experimental flow chart

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VI. EPS BLOCK PREPARING and CUTTING PROCESSES

Measured all EPS blocks length, width and height, the result is shown in Table 1; then cut each block into 10cm x 10cm x10cm cube, and marked by alphabetical in each plane (Table 2),

such coding marked on the specimen is used to indentify and analyze after the measurement.

Table 1. Size of test materials Table 2. Code of materials

The preparing and cutting steps are explaned as below:

1. Marked the relative position between EPS block and mold in the manufacture firm.

2. Measured dimension of EPS block, including length width and height, then measured

the weight of the entire EPS block, from the recorded data to calculate its unit weight (K

value).

3. In accordance with EPS blocks length, width and height planned to cut the size of each side, using ruler to draw the cutting line on each plane, then marked A1, A2 , A3.etc. in sequence on the first cutting surface.

4. After marked number, put the first cutting surface on the cutter sequentially cut into 10

cm3 specimens.

5. Similar with step 3 and step 4, marked and cut B1, B2 , B3.etc. In sequence on the second cutting surface.

6. Repeat step 5 to step 6, until all specimens were cut completely.

V. HOMOGEOUS TEST and ANALYSIS

In order to identify homogenous situation of the EPS block after foamed. Such activity can

avoid the engineering damage happened due to EPS inner defect once used the EPS material as

an embankment backfill. If the EPS production process has good and uniform quality, the unit

weight (K value) of EPS block before cutting should be the same with 10 cm3small cube specimen after cutting. If it has different result, it will mean that there is non-uniform problem in

the EPS molding process. In this study, tools of electronic scale and cursor caliper are used to

measure every cubes weight and volume. According to EPS suppliers specification, the

standard of unit weight is 0.2kN/m3(+0.015/-0.01). Table3 is the measured result of unit weight with Japanese EPS and Table4 is part of Taiwanese result.

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Table 3. Part of measured result of unit weight with Japanese specimens

Number Weight

(g)

Length

(cm)

Wide

(cm)

Height

(cm)

Volume

(cm3)

Unit

weight(kN/m3)

Difference

(+0.015/-0.01)

C2-20 17.88 9.846 8.209 9.874 798.07 0.219 +0.019

C9-20 18.19 9.889 9.809 8.342 809.18 0.220 +0.020

G2-20 18.8 9.923 9.994 8.448 837.79 0.219 +0.019

H2-20 18.77 9.854 9.837 8.359 810.26 0.227 +0.027

H3-20 18.54 9.858 8.403 9.827 814.03 0.223 +0.023

H5-20 18.84 9.866 9.828 8.462 820.50 0.225 +0.025

H9-20 18.38 9.873 8.442 9.815 818.05 0.220 +0.020

I10-12 19.78 9.075 9.873 9.883 885.49 0.218 +0.018

I10-13 20.02 9.117 9.861 9.868 887.16 0.221 +0.021

I10-14 20.01 9.017 9.853 9.888 878.49 0.223 +0.023

Table 4. Part of measured result of unit weight with Taiwanese specimens

Number Weight

(g)

Length

(cm)

Wide

(cm)

Height

(cm)

Volume

(cm3)

Unit

weight(kN/m3)

Difference

(+0.015/-0.01)

K1-18 22.03 9.994 9.848 10.119 995.92 0.2168649 +0.0168

K10-18 22.25 10.061 9.928 10.148 1013.63 0.2152021 +0.0152

O1-1 21.87 9.927 10.152 9.882 995.89 0.215 +0.015

O6-6 19.01 9.847 10.124 9.895 986.44 0.188 -0.011

O6-8 18.95 9.85 10.116 9.877 984.17 0.188 -0.011

O6-9 18.66 9.895 10.109 9.891 989.38 0.184 -0.015

O6-10 18.94 9.849 10.117 9.88 984.46 0.188 -0.011

O10-1 21.78 9.895 10.1 9.903 989.70 0.215 +0.015

VI. CONCLUSIONS

Two Japanese EPS blocks were cut to 2000 cubes and had 10 cubes non-compliance with

the standard. The location of the failed cubes are shown in Figure 9 and Figure 10; These 10

specimens do not meet specifications, but all of these are higher than 0.215 kN/m3.

Two Taiwanese EPS blocks were cut to 1080 cubes and had 557 cubes non-compliance

with standard. Meanwhile, there are 6 cubes density are lower than 0.199kN/m3 (Figure 11). The testing result shows that homogeneity quality of Taiwanese EPS blocks qualification rate is

only about 48%.

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Figure 9. Japanese D-20 (1) locations of

failure

Figure 10. Japanese D-20 (2) locations of

failure

Figure 11. Taiwanese D-20 locations of failure

Based on this study, homogeneity of the Japanese EPS is up to 99.5% passing rate, 10 failure of

the unit weight was higher than 0.215 kN/m3. Taiwan is only 48.4% pass rate, the studying result shows that Taiwan EPS manufacture quality still need to be improved.

This study uses heated 0.3mm Nickel-chromium wire to cut EPS specimens, Table 5 shows the

consumption rate of Taiwanese and Japanese EPS blocks. The consumption rate of Taiwan is up to

27.51% because the size of Taiwanese EPS is 184cm101cm67cm, but this study needs

10cm10cm10cm cube specimen, so Taiwanese EPS block just can cut to 180cm100cm60cm,

Therefore the consumption will be high.

Table 5. Consumption rate of cutting procedure

Test materials Weight(kg)

Total of

specimens

weight(kg)

Consumption(%)

Japan D-20(1) 20.68 19.49 5.74%

Japan D-20(2) 20.58 19.35 5.98%

Taiwan 20K 26.69 23.44 27.51%

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VII. REFERENCES

1. Lin Lee-kuo, The Supplying Condition of Aggregate and Application of EPS Construction Method in Taiwan. Proceedings of Conference on New Technique in Geotechnical Engineering. Taiwan,

R.O.C. p.1-17, 1998.

2. Bartlett S. Design of Geofoam Embankment for the I-15 Reconstruction. Proceedings of the Technique Conference of EPS Construction. p.10-1-10-10, 2000.

3. Negussey D. Properties and applications of Geofoam. Society of the Plastics Industry, Washington, D.C., 1997.

4. Frydenlund TE and Aaboe R. Expanded Polystyrene -The Light Solution. Proceedings of the International Symposium on EPS Construction Method, Tokyo, JP. p.383-388, 1996.

5. Lin Lee-kuo, Ch Li-hsie and Roger H. L. Chen, 2010.02, Evaluation of Geofoam as a Geotechnical Construction Material, ASCE Journal of Materials in Civil Engineering, J. Mat. In Civ. Engrgr. Volume 22, Issue 2, p.160-170, February 2010.

6. Lin Lee-kuo, Geofoam Practices in the use of the road slope, automation, efficiency and chemical methods and technologies applied to road side workshop, 1996.

7. Miki G. EPS Construction Method in Japan. Proceedings of the International Symposium on EPS Construction Method, Tokyo, JP, p.1-7, 1996.

8. Huang Bo-Wei, EPS Applicability of Disaster Prevention, National Taipei University of Technology, Master paper, 2003

9. Cheng Cho-Jen, Simulation and Analysis of EPS Impaction Test, National Taipei University of Technology, Master paper, 2010.

10. Duskov M. EPS as A Lightweight Sub-base Material in Pavement Structures. Ph.D. Thesis. Delft University of Technology, Netherlands, 1997.

11. Aaboe R. Evidence of EPS long-term performance and durability as a light weigh fill. Proceedings of the Transportation Research Board 79th Annual Meeting, Washington, D.C. p.21-27, 2000.

12. Horvath JS. Geofoam Geosynthetic: Past, Present, and Future. Electronic Journal of Geotechnical Engineer, p.25-27, 1996.

13. Horvath JS. Geofoam Geosynthetic. Horvath Engineering PC. Scarsdale, NY, 1995. 14. Norwegian Road Research Laboratory. Expanded Polystyrene Used in Road Embankments: Design,

Construction and Quality Assurance. Form 482E. Oslo. 1992.