The Properties of the Demolition Wastes and Their Inert Materials from
Chi-Chi Earthquake Damaged Structures
Chau-Ping Yang
Department of Civil Engineering and Engineering Informatics
Chung Hua University
707, Sec.2, WuFu Rd., Hsinchu, Taiwan 30012, R.O.C.
Tel.: +886-3-5186714
Fax.: +886-3-5372188
E-mail: ycp@chu.edu.tw
Abstract
More than 20 million cubic meters of demolition wastes arose as a result of the devastated Chi-Chi earthquake.
In order to reduce the site clearing costs, the inert materials (concrete, brick, pottery, and fine) mixed in the
demolition wastes should be reclaimed and recycled at that time, however, most of their properties were still
unknown. Therefore, this study investigates the properties of the demolition wastes and their inert materials
obtained from two earthquake demolition waste storage sites (Puli and Tali) and one normally urban construction
waste storage site (Taichung). It is found that the volumetric content of inert materials from earthquake
demolition waste is about 96%. Such inert material is classified as the excellent sub-grade rating, and can be
reused as sub-base and base soils.
Keywords: earthquake, demolition wastes, inert materials, properties.
1.
Introduction
Taichung county and Nan-Tou county. The huge
At 1:47 a.m. September 21st, 1999, a disastrous
amount of wastes then became a humungous task for
earthquake with a magnitude of 7.3 on the Richter
the government to remove and treat properly in order
scale struck Taiwan. Immediately after the earthquake,
to recover those sites. The task was particularly
the National Science Council of Taiwan mobilized
challenging because of the limited landfill sites in
more than 1,200 scientists and engineers to assess
Taiwan. Nevertheless, about 80 % of the demolition
various kinds of damage due to this earthquake. The
waste is comprised of available inert materials [2].
geotechnical hazards after the earthquake, including
The inert materials should be reclaimed from the
landslides, soil liquefaction, foundation failures, as
demolition wastes, and be recycled. By reusing these
well as ground movements were investigated, and the
materials, it is possible not only to reduce site
failures of bridges, dwellings, quay walls, as well as
clearing cost, but also to fulfill the partially demand
earth retaining structures were recorded [1].
for construction materials [3, 4, 5].
More than 20 million cubic meters of demolition
Taiwanese
government
have
implemented
wastes arose as a result of the devastated Chi-Chi
“Recycling and Reusing Act for Inert Materials” in
earthquake. Under the circumstance of emergency,
2000 to establish a regular system for treating
they were stored temporarily in several sites around
demolition wastes [6]. The Act mainly focuses on
administration
management,
yet
technological
As for the demolition waste of the Tali site, the
specifications for design and construction are hardly
content of inert material and impurity are 96.45% and
covered by this act. In practice, the specifications
3.55%, respectively. Although its composition is
involved in that act should be defined more
close to that of the Puli site, the content of concrete
concretely for inert materials. However, most of the
(51.02%) is higher than that of the Puli site (33.66%).
properties of inert materials from different areas were
The major sources were reinforced brick and concrete
still unknown. Thereby, the properties of the
building since the Tali city is a rather developed
demolition wastes and their inert materials ( particle
urban area.
diameter < 76.2 mm ) obtained from three storage
On the other hand, the content of inert material and
sites were studied in this paper. The three sites are
impurity of the demolition waste from the Taichung
Puli, Tali and Taichung. The test materials of the Puli
site are 78.61% and 21.39%, respectively. It is
site and Tali site were demolition wastes from
obvious that the impurity in the waste of the Taichung
Chi-Chi earthquake damaged structures, while that of
site is higher than those of the other sites, as the
the Taichung site was obtained from a regular
sources of the waste of the Taichung site were not
recycling factory, which was a normally urban
only from demolition buildings but also from
construction waste, and was tested for comparison
demolition interiors and dug earth works.
purpose.
Unit weights
2.
Properties of demolition wastes
Compositions
For investigating the unit weights of the above
mentioned materials, a shovel-type excavator was
For investigating the compositions of demolition
driven onto each hill to dig a shovel of the materials
wastes, a shovel-type excavator was driven onto each
at three points. Then the mixture of the three shovels
waste hill (see Figure 1). Where a shovel of wastes
of dug materials was loaded on a truck whose
3
(about 1.5 m ) were dug-up at three points with a
distance of about 50 m between two points. The
wastes in these three shovels were mixed and then
about 3,000
N of the mixture were sampled as the
test materials. First, the test materials were classified
into inert materials and impurities. The composite
materials sub-classified from impurities were metal,
glass, wood, paper, plastic, rubber, etc.
The contents measured by volume in the
demolition wastes from the three sites are listed in
Table 1. It is found that the content of inert material is
96.48% and that of impurity is 3.52% for the
demolition waste from the Puli site. Most of the
demolition waste was inert material because it was
container had a known volume. Moreover, the weight
of the mixture was measured so that the unit weight
can be obtained. The procedure was repeated for
three times to attain three sampled values of the unit
weight. Accordingly, the unit weight measured in this
way was under wet and loose condition. So that it is a
bulk unit weight.
The unit weights of demolition wastes, inert
materials, and impurities from the three sites are
listed in Table 2. Instead of standard deviation, the
statistic parameter of range of variation (  = the
maximum value – the minimum value) is used to
express the degree of variation of data because only
three values were measured for each item. The mean
unit weights of demolition wastes from the Puli site,
gathered from a mountainous area, and the major
sources were earth block building, reinforced brick
building, as well as light-steel houses.
Tali site, and Taichung site are 11.8 kN / m
0.5）, 14.0 kN / m
3
3
( =
(  = 0.4), and 9.1 kN / m
3
(  = 0.4), respectively. It is found that the unit
of inert materials from the three sites were tested, and
weight of the demolition waste from the Taichung
their particle-size distribution curves were obtained.
site is rather smaller compared with that of the other
Recycled inert material should be crushed and
sites because the former site contained greater
screened to produce useful construction soils that
impurities.
satisfy various specifications of earth structure reuses.
On the other hand, the mean unit weights of the
Thus, the gradation of inert material becomes a basic
impurities from the Puli site, Tali site, and Taichung
characteristic for laying out reclaimed machines and
site are 3.3 kN / m
(  = 0.2）, 2.8 kN / m
3
0.1）, and 3.0 kN / m
3
3
( =
(  = 0.3）, respectively. As
sieves. On the other hand, if the inert material is
directly reused as land backfill, embankment and
pavement without adjusting its gradation, then its
for the inert materials, the mean unit weights for the
properties of compaction and level of California
Puli
Bearing-Ratio (CBR) should be known.
site,
Tali
13.5 kN / m
3
site,
and
Taichung
(  = 0.5）, 14.8 kN / m
and 13.8 kN / m
3
(
3
site
are
(  = 0.3）,
 = 0.4） , respectively. The
Gradations
The gradations of inert materials from the three
values of unit weights of the impurities and inert
sites were tested according to ASTM D-136. Their
materials of the three sites are relatively close.
particle-size distribution curves are shown in Figure 2,
On the date of investigation, the moisture
and their engineering properties are listed in Table 3.
contents of demolition wastes from the Puli site, Tali
All of the inert materials are classified as “GP”
site, and Taichung site were 12.5%, 13.6%, and
(poorly
13.8%, respectively. It should be noted that the values
Classification System and as “A-1-a” by the
of unit weights of those materials may varied with
AASHTO Classification System. Note that according
weather conditions. The main cost of the reclamation
to the AASHTO Classification System, all the inert
project includes classification of demolition waste,
materials are judged as the most excellent sub-grade
treatment of inert material, and combustion of
rating. On the other hand, the percents of blocks
impurity. The cost is evaluated by weight, e.g., the
(diameter > 76.2 mm ) for the Puli site, Tali site ,and
product of volume and unit weight. As a result, the
Taichung site are 24, 37, and 21, respectively (see
measurements of those unit weights are important for
Figure 2). They should be crushed to produce useful
the reclamation project. As Taiwan is abundant in rain,
construction
it is suggested that the average unit weight should be
specifications. For example, the specified maximum
evaluated by two experiments, one on a day after
size of construction soil for land backfill, sub-grade
raining day and one on a dry sunning day.
and embankment is 150 mm [7, 8, 9].
3.
Compactions
Properties of inert materials
The
properties
of
inert
materials
were
Three
graded
gravel)
soils
inert
that
materials
by
the
satisfy
were
Unified
various
Soil
reuse
compacted
in
investigated in laboratory. However, due to the
accordance with the specification of modified Proctor
particle size limitation regulated by the related test
test (ASTM-D1557 Method D, compaction energy =
specifications for aggregate and soil, only the inert
2696 kJ / m )
materials passing through 76.2
mm sieve were
adopted as test materials. First of all, the gradations
3
in order to obtain their moisture
content-dry unit weight relationships (compaction
curves). The dry unit weight of a specimen
d
should be corrected by the content of over-size part,
12 h prior to the test. Upon test, it was compacted
because this method specifies the maximum size of
with efforts of 312 kJ / m , 937 kJ / m , and
testing material as 38.1
mm . Figure 3 shows the
3
2030 kJ / m
3
3
, respectively, to produce three
compaction curves of the three inert materials. The
compaction curves in moisture content-dry unit
specimens with different values of
d ,
which were
weight plane for the Puli site and Tali site are close.
then soaked. Subsequently, each soaked specimen
However, the compaction curve of the Taichung site
were placed in the compression machine and
is lower than those of the other two sites because
penetration reading were taken together with the
more light impurities and natural soils were contained
corresponding load reading. The CBR number (or,
in the inert material.
simply, the CBR) was obtained as the ratio of the
from
stress required to penetrate a certain depth into a
compaction curves (see Figure 3) are listed in Table 3.
soaked specimen over the standard stress, which
It is known that the optimum moisture contents wopt
corresponds to the same penetration depth on a
Those
compaction
results
obtained
standard sample of crushed stone. The same test
for the Puli site, Tali site, and Taichung site are 11.0%,
11.9%, and 15.7%, respectively. The values of the
maximum dry unit weights
sites are 19.4 kN / m
3
 d (max)
for these three
, 18.7 kN / m
3
procedure was done for the other two soaked
specimens. Thus, three sets of test data of (  d , CBR)
were obtained and they were plotted in the
, and
 d -CBR
plane, as shown in Figure 4, to calculated a linear
3
17.1 kN / m , respectively. The state at which the
regression equation. By using the equation, the CBR
optimum moisture content and maximum dry unit
numbers for two different compaction states of inert
weight is attained is generally referred to as the
“optimum compaction state”. Referring to the
“Specification of Public Construction – Earth Works”
enacted by the Public Project Mission of Taiwan, the
inert material can be used as construction soil only if
its value of
 d (max)
3
is larger than 14.7 kN / m .
Thus, the properties of compaction of the three inert
materials are above the required level.
materials,
 d  0.95 d (max)
and
 d =  d (max)
, can
be calculated.
For inert materials with dry unit weight of
( 0.95 d (max) ), the CBR numbers for the Puli site,
Tali site, and Taichung site are 62%, 59%, and 54%,
respectively (see Table 3). Moreover, for inert
materials with dry unit weights of
 d (max)
, the CBR
numbers for these three sites are 113%, 129%, and
Levels of CBR
103%, respectively. It is known that the compacted
Currently, the CBR test has been developed as
states largely affect their CBR numbers. According to
means of classifying the suitability of a soil for use as
“Manual of Highway Construction” enacted by the
a pavement course material in highway construction.
Taiwan Highway Bureau (1997), the required CBR
The CBR tests for the three inert materials were
numbers of sub-grade, sub-base, and base soil are
performed in accordance with the specification of
85%, 35%, and 15%, respectively. Therefore, under
ASTM-D1883. Accordingly, the inert material was
the case of ( 0.95 d (max) ), the inert materials from
mixed with the necessary amount of water to obtain
the requisite percentage of the optimum moisture
content and was stored in a sealed container for about
the three sites can be reused as sub-base and base
soil.
4.
Taiwan,
Conclusions
earthquake:
special
lecture.”
In
Proceedings of the 4th International Conference
The main conclusions from this study are
summarized as follows:
on Recent Advances in geotechnical Earthquake
(1) The volumetric content of inert material from
Engineering and Soil Dynamics, San Diego,
earthquake demolition waste is about 96%,
California., mass. pp. 26-31, Mar. 2001, Paper
which is significantly higher than that of 79%
SPL-10.1, University of Missouri-Rolla, Rolla,
from normally urban construction waste.
Mo.
(2) The mean unit weights of demolition wastes
from the Puli site, Tali site, and Taichung site are
3
3
3
11.8 kN / m , 14.0 kN / m , and 9.1 kN / m ,
[2].
Environmental
Protection
Administration,
Taiwan. (2000). Utilization of demolition waste
from Chi-Chi earthquake damaged structures.
Ch.3.
respectively.
(3) Three inert materials are classified by AASHTO
system as “A-1-a”, However their blocks should
be crushed to produce useful construction soils
[3]. Sorvari, J., (2003). “By-products in earth
construction:
environmental
assessments.”
Journal of Environmental Engineering, Vol. 129,
No.10, pp. 899-909.
that satisfy various reuse specifications.
(4) According to the properties of compaction of the
three inert materials, they can be re-used as
[4].Khalaf, F. M., and DeVenny, A. S., (2004).
“Recycling of demolished masonry rubble as
coarse aggregate in concrete: review.” Journal of
construction soils.
(5) Under the case of ( 0.95 d (max) ), the inert
materials from the three sites can be reused as
sub-base and base soil.
Materials in Civil Engineering, Vol. 16, No. 4, pp.
331-340.
[5]. Poon, C. S. and Chan, D., (2005). “Paving blocks
made with recycled concrete aggregate and
crushed clay brick.” Construction and Building
Acknowledgements
Materials, Vol. 20, No. 8, pp. 569-577.
This study is carried out under the financial
[6]. Construction & Planning Agency, Ministry of
support of the National Science Council, Taiwan
Interior, Taiwan. (2000). Recycling and Reusing
(NSC93-2211-E-216-003). Thanks are also given
Act for inert Materials.
to Public Construction Commission, Recovery
Committee
of
921
Chi-Chi
earthquake,
[7]. Sekine, E., and Ikeda, T., (2003). “Geotechnical
characteristics
of
crushed
concrete
for
Environmental Protection Administration, Water
mechanical stabilization.” Tsuchi To Kiso, Vol.
Resources
51, No. 5, pp. 31-33, Japan.
Agency,
Taiwan
Area
National
Expressway Engineering Bureau, related local
[8]. Shimoda, Y., (2003). “Plans to use construction
authorities and Jo-Mao Reclamation Company,
by-products as construction materials in Tokyo
Taiwan. The author also wishes to express his
Metropolitan.” Tsuchi To Kiso, Vol. 51, No. 5, pp.
gratitude to Mr. Jian-Hau Nae who helped field
22-24, Japan.
investigations presented in this paper.
[9]. Taiwan Highway Bureau. (1997). Manual of
Highway Construction. pp.15-21.
References
[1]. Ueng, T. S., Lin, M. L., and Chen, M. H., (2001).
“Some geotechnical aspects of 1999 Chi-Chi,
Table 1. Contents of demolition wastes from the three sites
Composite materials
Content by volume (%)
Puli site
Tali site
Taichung site
Inert
Concrete
33.66
material
Brick
25.59
Fine
37.23
24.84
46.37
Metal
0.06
0.02
0.002
Glass
0.12
0.07
0.007
Wood
2.54
Paper
0.12
0.56
1.43
Rubber and plastic
0.68
0.50
1.73
Impurity
51.02
96.48
20.75
96.45
21.49
3.52
11.49
3.55
2.40
78.61
21.39
18.22
Table 2. Unit weights of demolition wastes, impurities and inert materials
3
Unit weight ( kN / m )
Demolition waste
Impurity
Site
Measured
value
Mean
Range of
variation
11.6
Puli
11.7
Taichung
13.8
11.8
0.5
3.3
Measured
value
14.0
0.4
2.8
2.8
9.3
2.9
9.1
0.4
3.2
Range
of
Mean
variatio
n
13.5
3.3
0.2
3.1
2.9
13.8
9.1
Range
of
Mean
variatio
n
3.5
12.1
14.2
Tali
Measured
value
Inert material
13.3
13.5
0.5
14.8
0.3
13.8
0.4
13.8
15.0
2.8
0.1
14.7
14.7
0.3
3.0
8.9
3.0
Note：(1) The values of unit weights may varied with weather conditions;
(2) The moisture contents of demolition wastes from Puli site, Tali site and
Taichung site were 12.5%, 13.6% and 13.8%, respectively.
14.0
13.9
13.6
Table 3. Properties of inert materials from the three sites
Properties
Unified Soil Classification System
AASHTO Classification System
Puli
Optimum moisture content wopt (%)
Maximum dry unit weight
 d (max)
3
( kN / m )
CBR (%)
for specimens with  d  0.95 d (max)
Level of
CBR (%)
for specimens with  d   d (max)
Level of
GP
A-1-a
11.0
Tali
GP
A-1-a
11.9
Taichung
GP
A-1-a
15.7
19.4
18.7
17.1
62
59
54
113
129
103
Figure 1. Demolition waste in Puli site
100
90
Inert
materials
Mixed
Mixture
((■■:Puli)
:Puli)
Percent finer
finer (%)
Percent
(%)
80
70
60
50
((▲▲:Taichung)
:Taichung)
40
30
20
●:Tali)
(●(:Tali)
10
0
100
10
1
0.1
0.01
0.001
Particle
(mm)
Particlediameter
diameter (mm)
Figure 2. Particle-size distribution curves of inert materials from the three sites
21
33
3 ))
Dry
unit
Dry
weight
(kN/m
Dryunit
)
unitweight
weight (kN/m
(kN/m
Inert
materials
Mixture
Mixed
20
20
:Puli)
((■■:Puli)
19
(●:Tali)
(● :Tali)
18
(▲
▲:Taichung)
:Taichung)
17
16
7
9
11
13
15
17
19
21
Moisturecontent
content (%)
(%)
Moisture
Figure 3. Compaction test results of inert materials from the three sites
20.0
20.0
Mixed
Mixture
Inert
materials
3
3)
Dry
weight
(kN/m
3 )
Dry unit
unit
weight
3
Dry
weight (kN/m
(kN/m
Dryunit
) )
density
(kN/m
19.5
19.5
Puli(█
):):y=0.018x
Puli(
+17.386
y = 0.0179x+17.39
■
19.0
19.0
18.5
18.5
18.0
18.0
Tali(
●):y=0.013x
●):
Tali(
+17.041
y = 0.0129x+17.04
17.5
17.5
17.0
17.0
16.5
16.5
Taichung(
): ):y=0.018x
▲▲
Taichung(
+15.267
y = 0.0178x+15.27
16.0
16.0
15.5
15.5
20
20
40
40
60
60
80
80
100
100
120
120
140
140
160
160
180
180
CBR(%)
CBR
(%)
Figure 4. The relationships between CBR and dry unit weight of inert
materials from the three sites