Nghiên cứu sử dụng xỉ thép khu vực bà rịa – vũng tàu trong xây dựng đường ôtô tt tiếng anh

MINISTRY OF EDUCATION AND TRAINING
UNIVERSITY OF TRANSPORT AND COMMUNICATIONS

MAI HONG HA

RESEARCH ON USING RECYCLED
STEEL SLAG IN BA RIA VUNG TAU
FOR ROAD CONSTRUCTION
Field of study
Code
Speciality

: Transport engineering
: 9580205
: Highway and urban road engineering

SUMMARY OF DOCTORAL THESIS

HA NOI – 2019


This research is completed at :
University of transport and communications

Supervisors:
AssocProf.Dr. La Van Cham
University of Transport and Communications

Reviewer 1:
Reviewer 2:
Reviewer 3:

The thesis will be defended before Doctoral-Level Evaluation
Council at University of Transport and Communications
at …..hours……Day……Month……Year…….

The thesis can be read at :
1. National Library of Vietnam
2. Library of University of Transport and Communications


1

INTRODUCTION
1. Rationale
According to the development planning for Viet Nam Steel Industry during
2007 – 2015 with a vision until 2025, if the steelmaking factories in South Vietnam
alone all operated with the capacity of 4-5 million tons/year, then they would
discharge approx. 1 million tons of steel slag each year. An average of 0.5-1.0
million tons per year of steel slag is discharged in Viet Nam and in Ba Ria -Vung
Tau province, the amount is about 0.3-0.5million tons/year. Unless there were
proper solutions to reuse this source of waste, the storage would be costly and plenty
of land would be wasted. While automobile road construction is in need of various
kinds of materials, these traditional natural material are becoming scarce.
Therefore, the thesis “Research on using recycled steel slag in Ba Ria-Vung
Tau for road construction” is esential with scientific and practical significance.
2. Aims of the research
To study experiences of many countries in the world in using steel slag as an
aggregate in road pavement construction;
To combine the theoretical research with analysis of experiments in lab and
on site on recycling steel slag from steel factories in Ba Ria-Vung Tau in roadbase

construction;
On that basis, to evaluate possibility of replacing macadam aggregate by steel
slag in roadbase construction and propose pavement structures using steel slag
recycled from the steel factories in Ba Ria-Vung Tau.
3. Targets and scope of the research
- The physio-mechanical properties and technical specifications necessary for
design, construction and acceptance of roadbase and pavement using recycled steel
slag from electric arc furnace steel factories in Ba Ria-Vung Tau; and
- Suitable reinforcement solutions to improve the physio-mechanical
properties of steel slag to satisfy technical requirements of aggregates in road base
construction in Ba Ria-Vung Tau.
4. Scientific and practical significance
4.1. Scientific significance
- The experiment results have proved that it is possible to use the recycled steel slag
from steel factories in Ba Ria-Vung Tau as aggregate for roadbase layers;
- The effectiveness of cement reinforcement with 3 types of aggregate; steel slag,
steel slag with fine sand and steel slag with stone dust has been analyzed. A suitable
ratio of 4-6% cement by mixture mass is recommended.


2
4.2. Practical significance
- Having determined the technical specifications of steel slag from steel
factories in Ba Ria-Vung Tau to be recycled in roadbase construction;
- Having proposed some pavement structures using recycled steel slag from
steel factories in Ba Ria-Vung Tau; and
- Having contributed to enriching the knowledge on using steel slag for
roadbase construction in Viet Nam, and serving as good reference for research
and teaching on materials and pavement structures.
5. Outline of the research

The thesis is comprised of the Introduction, 4 main chapters, the Conclusions
and Recommendation, the Direction for Furrther Research, the Reference and the
Appendix.

OVERVIEW OF STEEL SLAG AND ITS USE IN ROAD CONSTRUCTION

1.1. Steel slag
Steel slag, a by-product of steel making, is produced during the process of the
molten steel being separated from impurities in the steel-making furnace. The slag
occurs as a molten liquid which melts and is a complex dissolving process of
silicates and oxides but it solidifies upon cooling. Steel slag formation process looks
like lava eruption, thus steel slag is called ‘artificial magma’ in scientific reports
overseas.
1.2. Studies on steel slag overseas
1.2.1. Chemical properties
1.2.1.1. Chemical composition
Ana Mladenović, Tahir Sofilić, R. Alizadeh, H. Motz, etc. have analyzed the
chemical and mineral composition of steel slag in their studies.
 The chemical composition of steel slag includes CaO, Fe xO y, MgO,
MnO 2, SiO 2 and Al 2 O3 , in which the main substances are CaO, SiO 2 và Fe x O y,
accounting for about 80% of the steel slag weight.
 The mineral composition of steel slag includes Wustite (FeO), Calcium
Silicates (2CaO.SiO 2, C2 S and 3CaO.SiO 2, C3S), Brownmillerite
(Ca 2 (Al,Fe) 2O 5 ,C 4 AF) and Mayenite (12CaO.7Al 2 O 3, C12 A7 ).
1.2.1.2. Physical and mechanical properties
The physio-mechanical properties of steel slag have been investigated by
many scientists overseas like Gurmel from the UK; Lykoudis, V. Maruthachalam


3

from Greece, Tahir Sofilić from Croatia, Maslehuddin from Saudi Arabia, H. Motz
from Germany, etc. The study results show that the specific gravity of steel slag is
between 3.3-3.5 g/cm3, the porous bulk density is 1500kg/m3, the voids is 31-45%,
the water absorption is 1-2%, and the pH degree is 10-12.
1.2.2. Oversea studies on steel slag used as aggregate in roadbase
construction
According
to
EUROSLAG,
the
amount of steel slag
discharged in 2010
was about 21.8 million
tonnes, 87.0% of
which was reused. In
some
European
countries,
like
Figura 1.11 Applications of steel slag in Europe
Germany and France,
the reuse rate was over 90%. In general, about 48.0 % of the steel slag was used in
road construction while the rate was 32.4% in Japan, 49.7% steel slag of the United
States was used for the upper and lower roadbase, 16% was used as aggregate for
asphalt concrete, and in China the rate was approx. 29.5%.
According to Ebenezer Akin Oluwasola, steel slag is qualified to serve as
aggregare for lower roadbase construction due to its high internal friction and
draining ability.
To increase the reuse rate of steel slag in China, Weiguo Shen [37]
experimented to use steel slag reinforced with fly ash and phosphogypsum (a waste

by-product from production of phosphoric acid and phosphate fertilizer) in upper
roadbase construction. The experiment results show that the compressive strength
of the reinforced samples has increased from 1.86MPA at Day 7 to 8.38MPA at Day
28, completely meeting Chinese standards of the upper roadbase. The splitting
tensile strength and elastic modulus are a little lower than those of cementreinforced macadam, but much exceed Chinese requirements set in “Specifications
of Asphalt Pavement Design for Highway- JTJ014-97”.
Besides, many other scientific studies in the world all acknowledge that steel
slag can be applicable to road construction, e.g. aggregate for asphalt concrete,
surface for low-grade roads, or upper and lower roadbase for pavement.
1.3. Inland studies on steel slag
In Viet Nam, the initial legal documents and standards have acknowledged


4
applicability of steel slag in road construction, e.g. TCVN 6705:2009; Document
No. 31/BXD-VLXD dated June 07, 2011 by Vietnam Ministry of Construction;
Decision No. 430/QĐ-BXD promulgating the technical specifications of “Cast iron
and steel slag used as buliding materials”.
According to Le Thanh Truong , after melted in the electric arc furnace at
1600oC, steel slag has similar mineral composition to that of cement, which is not
available in natural materials.
The Green Materials Ltd. Co. has sent steel slag samples to VILAS laboratory
to analyze and identify hazardous components. The analysis results when compared
with QCVN 07:2009/BTNMT reveal that the inorrganic hazardous components
have not been detected or if present, fall much lower than the limit value.
In his doctoral thesis, Nguyen Van Du studied steel slag to replace coarse
aggregate in asphalt concrete.
In 2011, Dr. Tran Van Mien and his partners from the Material Section,
HCMC University of Technology in coordination with Le Phan Company Lld. Co.
conducted a study on use of steel slag as aggregate to replace macadam in asphalt

concrete.
From 2013 to 2015, the Ministry of Transport assigned HCMC University of
Transport to implement a ministry-level research project entitled “Study on steel
slag from steel factories to be recycled as a material in roadbase construction” led
by Dr. Nguyen Quoc Hien and me, a doctoral candidate as the main participant. The
project was accepted and graded Level B by the Minisstry of Transport. The project
results and recommendations are as follows.
 Steel slag can absolutely be recycled as a building material in
production of cement concrete, asphalt concrete and in roadbase construction;
 If steel slag is processed by a suitable technology, it can be used in the
road subbase layers according to the aggregate principle like Grade II
macadam.
1.4. Objectives of the research
To study the properties of steel slag after recyled from the steel factories in Ba
Ria - Vung Tau (BRVT) to be used in roadbase construction.
To investigate solutions to improve the physio-mechanical properties of steel
slag so that it can satisfy the technical requirements when used as aggregate for
various roadbases.


5

RESEARCH ON PHYSICAL, MECHANICAL AND CHEMICAL
PROPERTIES OF RECYCLED STEEL SLAG

2.1. Studying properties of steel slag discharged at steel factories in Ba RiaVung Tau
The steel slag under survey, study and evaluation comes from the Electric Arc
Furnace (Electric Arc Furnace steel slag is abbreviated as EAF steel slag)
The recyled steel slag samples are collected from the building material factory
of the Green Materials Ltd. Co. (located in Tan Thanh district, Ba Ria-Vung Tau

province)
2.1.1. Steel slag properties
Within the research scope, in comparison with the related standards, a survey
of the physio-machenical properties of steel slag, including particle composition,
specific gravity, bulk gravity, and so on has been conducted in addition with an
analysis of its chemical composition.
2.1.2. Testing results
Testing results are summarized in Table 2.5:

Specific gravity
Bulk dry specific
gravity
Bulk saturated
surface dry
specific gravity
Water absorption
Bulk density
Voids
Moisture
Maximum bulk
dry specific
gravity (proctor
compaction test)
Index: Wl; Ip; PP
Content of dust,
mud and clay
Los Angeles
abrasion and
impact

Sample
10

Sample
9

Sample
8

Sample
7

Sample
6

Sample
5

Sample
4

Sample
3

Unit

Sample
2

Testing

specification

Sample
1

Table 2.5: Physio-machenical properties of steel slag

g/cm3

3.47

3.66

3.66

3.68

3.50

3.52

3.41

3.55

3.58

3.49

3

3.29

3.35

3.34

3.42

3.19

3.29

3.16

3.28

3.30

3.23

g/cm3

3.34

3.44

3.42

3.49

3.28

3.36

3.23

3.36

3.38

3.31

%
kg/m3
%
%

1.54
1823
47.5
2.98

2.52
1877
48.7
3.41

2.61 2.10 2.81 1.96 2.31 2.26 2.38 2.26
1906 1837 1975 1799 1806 1874 1886 1800

47.8 50.1 43.6 48.9 47.0 47.2 47.4 48.4
3.62 3.54 3.57 3.67 3.54 3.65 3.37 3.42

g/cm3

2.36

2.43

2.48

2.45

%

0.4

1.2

1.6

0.6

%

22

22

21

22

g/cm

2.50

2.50

2.50

2.45

2.43

2.43

1.6

0.5

0.7

1.2

1.1

0.7

22

19

21

22

21

22

none


Sample
5

Sample
6

Sample
7

Sample
8

Sample
9

Sample

10

%

Sample
4

Elongation and
flakiness content
Elastic modulus
In-lab CBR (K =
0.98)

Sample
3

Unit

Sample
2

Testing
specification

Sample
1

6

0.8

1.1

1.2

0.9

0.7

0.6

1.8

0.3

1.6

1.0

MPa 225.88 230.59 226.74 285.17 231.57 239.60 244.71 232.70 318.80 246.23
%

111.58 90.35 85.92 88.98 90.28 117.98 89.07 103.86 98.24 93.30

Table 2.6 Particle composition of steel slag
Remain (%)

Sample
4

Sample
5

Sample
6

Sample
7

Sample
8

Sample
9

Sample
10

100

Sample
3

<0.075

Sample
2

50
37.5

25
19
9.5
4.75
2.36
0.425
0.075

Sample
1

Size sieve
(mm)

0.0
0.0
6.3
13.5
39.9
63.7
81.1
96.4
99.6

0.0
1.8
12.3
20.5
47.6
72.6

87.0
98.2
99.7

3.2
4.1
9.1
14.6
39.9
64.1
80.4
94.7
98.3

0.0
3.5
10.7
16.5
39.6
63.1
80.8
97.1
99.2

0.0
2.9
9.6
16.6
46.6
71.1

85.8
95.6
98.9

0.0
2.6
16.3
27.6
59.2
78.3
89.7
97.2
99.4

0.0
2.7
16.8
31.6
63.3
83.1
94.1
99.0
99.6

0.0
1.8
12.3
20.5
47.6
72.6

87.0
98.2
99.7

0.0
2.9
9.6
16.6
46.6
71.1
85.8
95.6
98.9

0.0
4.3
7.8
15.0
40.9
66.2
84.8
97.4
99.3

100

100

100

100

100

100

100

100

100

Table 2.7 Chemical composition of steel slag
Sample
1

Sample
2

Sample
3

Sample
4

Sample
5

Sample
6

Sample
7

Sample
8

Sample
9

Sample
10

Oxide composition (%)
Oxide
SiO2
Al2O3
Fe2O3
CaO
MgO
SO3

16.20
8.00
35.80
28.30
5.40
-

16.60

8.10
34.80
28.20
5.50
-

17.38
7.85
35.47
23.96
11.43
0.09

18.86
8.75
35.25
21.66
12.36
0.12

13.50
6.60
38.80
26.10
6.10
-

16.10
6.70
35.50

26.20
5.10
-

18.50
7.40
34.40
25.40
4.70
-

17.00
7.76
35.02
23.47
5.04
0.09

13.32
8.17
35.53
25.61
5.40
0.10

16.70
6.26
34.02
23.20
5.98

0.13

2.2. Analysis, evaluation and remarks of the testing results
2.2.1. Statistical analysis
Minitab 18 Statistical Software was used to analyse the results shown in the
table below.


7
Table 2.8 Steel slag properties
Oder
1
2
3
4
5
6
7
8
9
10
11
12
13
14

Testing specification

g/cm3
g/cm3

g/cm3
%
Kg/m3
%
%
%
%

Mean
value
3.552
3.285
3.361
2.275
1858.3
48.28
0.953
21.36
1.00

Standard
deviation
0.0913
0.0771
0.0771
0.3561
56.4
2.42
0.443
0.971

0.45

g/cm3

2.458

0.038

%
%
%
MPa

3.474
0
96.96
248.2

0.204
10.824
30.24

Unit

Specific gravity
Bulk dry specific gravity
Bulk saturated surface dry specific gravity
Water absorption
Bulk Density
Voids

Content of dust, mud and clay
Los Angeles abrasion and impact
Elongation and flakiness content
Maximum bulk dry specific gravity (Proctor
compaction test)
Optimum moisture
Expansion characteristics
In-lab CBR (K = 0.98)
Elastic modulus

Table 2.9 Chemical composition of steel slag
Oder
1
2
3
4
5
6

Testing specification
Silicon oxide content (SiO2)
Aluminium oxide content (Al2O3)
Iron oxide content (Fe2O3)
Canxi oxide content (CaO)
Magie oxide content (MgO)
Sulfate, sulfit content

Unit
%
%

%
%
%
%

Mean value
16.416
7.56
35.46
25.21
6.692
0.104

Standard deviation
1.824
0.80
1.30
2.152
2.76
0.017

2.2.2. Steel slag physio-machenical properties compared and evaluated
against macadam in roadbase construction
The results given above show that the physio-machenical properties of
recycled steel slag from the steel fatories in BRVT are similar to those of macadam
aggregate in the southeastern region. Compared with TCVN8859:2011 for
“Macadam aggregate roadbase in road pavement: aggregates, construction and
acceptance”, most specifications of steel slag satisfy the technical requirements of
Class I macadam aggregate (except for the CBR index).
2.2.3. Evaluation and remarks of the chemical composition of steel slag

Properties of steel slag depend on M0 ratio (a ratio between the sum of CaO
and MgO content compared with the sum of SiO2 and Al2O3 content available in
steel slag):


8
𝐶𝑎𝑂 + 𝑀𝑔𝑂
25.21 + 6.692
=
= 1.33
𝑆𝑖𝑂2 + 𝐴𝑙2 𝑂3 16.416 + 7.56
When Mo >1, steel slag is alkaline, so if it is used as aggregate, it must be
reinforced by cement or lime.
2.2.4. Evaluation and remarks of steel slag’s effect on the environment
Based on the research results stated in the Overview and earlier in this chapter,
some remarks and evaluation are given below.
 Steel slag does not contain substances harmful to the environment
(according to the research by Tahir Sofilić);
 Radionuclides content found in steel slag is lower than the limit
(according to Decision No. 430/QĐ-BXD dated May 16, 2017 by the Ministry
of Construction);
 Testing and analysis results of the recylced steel slag from the steel
factories in BRVT province show that hazardous substances are not detected
or lie within the limit range.
2.3. Conlusions of Chapter 2
(1)
The physio-machenical properties of recycled steel slag from the steel
factories in BRVT are similar to those of macadam aggregate in the
southeastern region, a common material in roadbase construction. According
to TCVN8859:2011, most specifications of steel slag meet the technical

requirements of Class I macadam aggregte (except for the CBR index);
(2)
Due to the characterisitics of steel slag and the recycling technology
currently in use in BRVT, the steel slag aggregate lacks small sized particles
(<0.425mm) for pore filling, so it is difficult to achieve density.
(3)
Steel slag is alkaline, so there should be further study on its reinforcement
with cement or lime in order to maximize its alkaline properties and increase
the bearing capacity of roadbase; and
(4)
From the above analysis, it is possible to recycle steel slag from the steel factories
in BRVT to replace macadam aggregate in the subbase of road pavement.
𝑀𝑜 =

LAB-BASED EXPERIMENTS TO DETERMINE TECHNICAL
SPECIFICATIONS OF CEMENT-REINFORCED STEEL SLAG IN
ROADBASE CONSTRUCTION

The content presented in Chapter 1 and Chapter 2 has proved that recycled steel slag
from the steel factories in BRVT can be used as aggregate in roadbase construction.


9
However, based on the research results given in Chapter 2, steel slag is suitable
for the subbase of pavement. Due to the characterisitics of steel slag and the
recycling technology currently in use in BRVT, the steel slag aggregate lacks small
sized particles (<0.425mm) for pore filling, so it is difficult to achieve density,
which may possibly reduce the structure’s bearing capacity.
To improve aggregate made of steel slag and promote its alkalinity aiming at
extending its application to the upperbase of pavement, the doctoral candidate has

investigated various solutions for steel slag reinforced with fine sand, stone dust and cement.
3.1. Materials for reinforcement
3.1.1. Steel slag
Steel slag from the steel factories in Ba Ria Vung Tau is collected and recycled
by the Green Materials Ltd. Co. with the physio-mechanical properties presented in
Chapter 2.
3.1.2. Cement
The cement used for experiments is HaTien cement.
3.1.3. Water
The water in experiments is the tap water, satisfying the technical requirements
of concrete and mortar according to TCXDVN 302-2004.
3.1.4. Fine sand
The fine sand used in the research is natural sand taken from Dong Nai river,
with the physio-mechanical and chemical properties shown in Table 3.2.
Table 3.2: Physio-mechanical and chemical properties of fine sand
Oder
1
2
3
4
5
6
7
8
9
10
11

Testing specification
Specific gravity

Bulk specific gravity
Voids
Bulk density
Water absorption
Organic impurities
Content of dust, mud and
clay
Silica content
Chloride content ClSulfate and sulfite content
Mica content

Unit
g/cm3
g/cm3
%
g/cm3
%
Standard
reference
color

Standard
TCVN 7572-4 : 2006
TCVN 7572-4 : 2006

%

TCVN 7572-8 : 2006

2.08

mol/l
%
%
%

TCVN 7572-19 : 2006
TCVN 7572-12 : 2006
TCVN 7572-16 : 2006
TCVN 7572-20 : 2006

62.86
0.007
0.012
0.01

TCVN 7572-6 : 2006
TCVN 7572-4 : 2006
TCVN 7572-9 : 2006

Result
2.67
2.5
46.20
1345
2.58
equal
standard
colour

3.1.5. Stone dust
Stone dust is a byproduct of running stones through a crushing machine to
make crushed stones of 1×1 stone, 1×2 stone or 4×6 stone.


10
Table 3.4: Physio-mechanical and chemical properties of stone dust
Oder

Testing specification

Unit

1

Specific gravity

g/cm3

2

Bulk specific gravity

g/cm3

3

Voids

4

Bulk Density

5

Water absorption

%
g/cm
%
Comparing
colour

Organic impurities

7

Content of dust, mud and
clay

%

8

Dry compressive Strength

MPa

9
10

MPa
%

Result
2.782
2.624
41.01

3

6

Saturated compressive
Strength
Los Angeles abrasion and
impact

Standard
TCVN 7572-4 :
2006
TCVN 7572-4 :
2006
TCVN 7572-6 :
2006
TCVN 7572-4 :
2006
TCVN 7572-9 :
2006
TCVN 7572-8 :

2006
TCVN 757210:2006
TCVN 757210:2006
TCVN 757212:2006

1.548
0.56
Equal standard
colour
0.74
209.1
193.6
14.1

3.2. Selecting proper mixing ratio to improve steel slag aggregate
The researcher has analyzed and evaluated the particle composition of the
material mixtures with different steel slag ratios. The aggregate curve that is closest
to Fuller curve will be selected as the basis for research in the next steps. The results
are as follows.
- The mixing proportion between steel slag and fine sand providing the
aggregate closest to Fuller curve is 80% upon 20%.
- The mixing proportion between steel slag and stone dust providing the
aggregate closest to Fuller curve is 70% upon 30%.
3.3. Experimenting solutions in lab to reinforce steel slag with cement, fine
sand and stone dust
3.3.1. Sample making method
Steel slag is reinforced with 4-10% cement. Each combination includes 36
samples, of which 24 samples are made by modified Proctor mould (height of
11.7cm and diameter of 15.2cm) to test the compressive strength and the splitting
tensile strength and 12 samples are made by standard mould (height of 11.7cm and

diameter of 10.16cm) to test the elastic modulus.
3.3.2. Analyzing experiment results on cement-reinforced steel slag


11
Table 3.8: Experiment resuls on cement-reinforced steel slag
Std
Order
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22

23
24
25
26
27
28
29
30
31
32
33
34
35
36

Run
Order
1
2
3
4
5
6
7
8
9
10
11
12
13

14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36

Pt
Type
1
1
1
1

1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1

1
1

Blocks

XM

Age

Rn (MPa)

Rech (MPa)

E (MPa)

1
1
1
1
1
1
1
1
1
1
1
1
1
1
1

1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1

4
4
4
4

7
14
28

56
7
14
28
56
7
14
28
56
7
14
28
56
7
14
28
56
7
14
28
56
7
14
28
56
7
14
28
56
7

14
28
56

4.48
4.76
6.42
6.41
4.96
5.55
6.60
7.69
5.29
6.13
11.17
12.36
5.63
7.26
15.93
16.93
4.85
4.73
5.47
6.31
4.69
4.89
7.43
7.67
5.09
5.33

11.79
11.94
4.94
6.34
14.25
16.98
4.25
4.49
6.14
5.88

0.066
0.069
0.090
0.117
0.067
0.083
0.152
0.165
0.078
0.124
0.350
0.445
0.110
0.134
0.969
1.108
0.061
0.076
0.083

0.078
0.065
0.091
0.127
0.139
0.090
0.131
0.402
0.443
0.115
0.146
0.889
1.079
0.063
0.080
0.098
0.099

456.32
507.99
710.63
741.30
598.42
595.55
908.74
945.93
808.72
825.40
1302.68
1408.16

843.94
1075.29
1584.79
1737.72
519.31
461.21
689.42
742.40
577.72
577.32
862.54
921.51
792.77
901.92
1260.91
1409.76
901.80
977.50
1605.77
1701.53
459.12
492.85
727.73
728.59

6
6
6
6
8

8
8
8
10
10
10
10
4
4
4
4
6
6
6
6
8
8
8
8
10
10
10
10
4
4
4
4


12

Std
Order
37
37
38
39
40
41
42
43
44
45
46
47
48

Run
Order
37
37
38
39
40
41
42
43
44
45
46
47

48

Pt
Type
1
1
1
1
1
1
1
1
1
1
1
1
1

Blocks

XM

Age

Rn (MPa)

Rech (MPa)

E (MPa)

1
1
1
1
1
1
1
1
1
1
1
1
1

6
6
6
6
6
8
8
8
8
10
10
10
10

7
7

14
28
56
7
14
28
56
7
14
28
56

5.17
5.17
5.28
6.83
6.84
4.85
5.18
10.56
12.00
5.83
6.45
15.17
16.79

0.074
0.074
0.102
0.134

0.155
0.085
0.118
0.436
0.489
0.102
0.142
0.822
1.056

567.40
567.40
603.49
935.47
953.94
775.83
826.91
1394.79
1436.59
880.25
951.02
1520.85
1742.71

3.3.3. Analyzing experiment results on steel slag-fine sand mixture
(80%/20%) and cement-reinforced
The results done by Minitab are summarized in Table 3.9 for analysis.
Table 3.9 Experiment resuls on steel slag-fine sand mixture cement-reinforced
Std
Order

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21

Run
Order
1
2
3
4
5
6

7
8
9
10
11
12
13
14
15
16
17
18
19
20
21

Pt
Type
1
1
1
1
1
1
1
1
1
1
1
1

1
1
1
1
1
1
1
1
1

Blocks

XM

Age

Rn (MPa)

Rech (MPa)

E (MPa)

1
1
1
1
1
1
1
1

1
1
1
1
1
1
1
1
1
1
1
1
1

4
4
4
4
6
6
6
6
8
8
8
8
4
4
4
4

6
6
6
6
8

7
14
28
56
7
14
28
56
7
14
28
56
7
14
28
56
7
14
28
56
7

3.42
4.70

6.04
6.41
8.45
9.82
12.01
12.72
10.99
12.26
15.81
17.40
4.15
4.23
5.84
6.33
8.76
10.15
12.52
11.35
10.63

0.099
0.165
0.297
0.336
0.620
0.766
0.944
0.827
1.012
1.181

1.347
1.669
0.074
0.158
0.309
0.315
0.617
0.649
0.819
0.890
0.994

1220.96
1233.31
1308.51
1326.99
1516.45
1584.22
1749.25
1776.59
1589.75
1584.76
1775.43
1941.99
1221.57
1239.28
1303.36
1326.84
1533.78
1562.28

1605.17
1768.89
1571.36


13
Std
Order
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36

Run
Order
22
23
24
25

26
27
28
29
30
31
32
33
34
35
36

Pt
Type
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1

Blocks

XM

Age

Rn (MPa)

Rech (MPa)

E (MPa)

1
1
1
1
1
1
1
1
1
1
1
1
1
1
1

8
8

8
4
4
4
4
6
6
6
6
8
8
8
8

14
28
56
7
14
28
56
7
14
28
56
7
14
28
56

11.80
14.28
16.40
3.84
4.58
6.72
7.06
8.29
9.46
10.79
12.11
10.78
12.74
15.87
16.62

1.217
1.370
1.718
0.079
0.172
0.288
0.324
0.560
0.724
0.890
0.954
0.976
1.110
1.438

1.609

1698.96
1890.35
1922.39
1212.85
1229.77
1307.06
1319.01
1549.82
1522.70
1776.57
1704.94
1630.28
1603.67
1920.70
1944.85

3.3.4. Analyzing experiment results on steel slag-stone dust mixture
(70%/30%) and cement-reinforced
The results done by Minitab are summarized in Table 3.10 for analysis.
Table 3.10 Experiment resuls of steel slag-stone dust mixture cement-reinforced
Std
Order
1
2
3
4
5
6

7
8
9
10
11
12
13
14
15
16
17
18
19
20
21

Run
Order
1
2
3
4
5
6
7
8
9
10
11
12

13
14
15
16
17
18
19
20
21

Pt
Type
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1

1
1
1

Blocks

XM

Age

Rn (MPa)

Rech (MPa)

E (MPa)

1
1
1
1
1
1
1
1
1
1
1
1
1
1

1
1
1
1
1
1
1

4
4
4
4
6
6
6
6
8
8
8
8
4
4
4
4
6
6
6
6
8

7
14
28
56
7
14
28
56
7
14
28
56
7
14
28
56
7
14
28
56
7

9.12
9.39
11.67
11.79
12.12
14.11
16.67
16.77

17.60
19.24
24.63
25.98
8.98
9.42
11.45
11.52
12.35
12.73
17.44
17.21
17.38

0.531
0.616
0.751
0.809
0.858
1.001
1.251
1.431
1.912
2.064
2.540
3.357
0.528
0.604
0.737
0.809

0.850
0.910
1.117
1.425
1.951

1397.41
1423.87
1469.39
1506.57
1680.65
1650.34
1803.15
1841.23
1895.51
1952.45
2073.63
2041.20
1392.15
1416.64
1469.19
1510.33
1695.50
1803.97
1775.16
1802.55
1897.65


14

Std
Order
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36

Run
Order
22
23
24
25
26
27
28
29
30
31

32
33
34
35
36

Pt
Type
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1

Blocks

XM

Age

Rn (MPa)

Rech (MPa)

E (MPa)

1
1
1
1
1
1
1
1
1
1
1
1
1
1
1

8
8
8
4
4
4
4
6

6
6
6
8
8
8
8

14
28
56
7
14
28
56
7
14
28
56
7
14
28
56

19.18
24.95
25.79
9.09
9.69
11.68

12.09
11.83
13.69
16.51
18.85
17.22
19.48
24.52
25.93

2.044
2.573
3.329
0.522
0.604
0.738
0.818
0.842
0.966
1.062
1.384
1.921
2.048
2.567
3.337

1975.84
2063.32
2051.39
1392.98

1423.87
1465.87
1487.06
1688.39
1650.07
1804.59
1790.57
1971.07
1910.82
2014.40
2112.16

3.3.5. Analyzing and comparing the solutions using steel slag reinforced with
cement
Using Minitab 18 for Design of Experiments
Analysis functions include Compressive Strength (Rn), Splitting Tensile
Strength (Rech) and Elastic Modulus(E).
3.3.5.1. Analysis of the compressive strength Rn
The compressive strength of steel slag (XT), steel slag-fine sand (XC), steel
slag-stone dust (XD) all reinforced with cement are shown in the figures below.

a) Main elements‘ effect
b) Interactive effect
Figure 3.31: Diagram of elements‘effect on Rn

Figure 3.31 shows that all the 3 elements (aggregate, cement ratio, age) have
much effect on Rn.
- Effect by aggregate: The ascending
order Rn by aggregate is
XTXCXD;

- Effect by cement ratio: When cement ratio increases, Rn increases too, at a


15
relatively steady rate when cement increases from 4% to 8% illustrated by the
rather equally slopy lines in the figure;
- Effect by age: During the first stage of 7-14 days of age, the compressive
strength develops slowly, between Day 14 and Day 28, the rate accelerates
illustrated by the slopy line in the diagram of Strength versus Age, however,
from Day 28 to Day 56, Rn gains slowly. The diagram of effect by age on
compressive strength is not linear, but of quadratic relation;
- The interactive effects by age and cement ratio are basically similar.
However, with 6%, 8% cement, on Days 28 and 56, the effect is more obvious.
Figure 3.32 is a general diagram
of compressive strength Rn versus
cement ratio and age. At Day 14, the
compressive
strength
exceeds
4.0MPa.
3.3.5.2. Analysis of the splitting
tensile strength Rech
Similarly conducted as desribed
above, the splitting tensile strength of
Figure 3.32: General diagram of Rn
cement reinforced XT, XC and XD is
cement reinforced XT, XC and XD
depicted in Figure 3.33. Its changing
rule is similar to that of Rn.

b)Interactive effect
a) Main elements‘ effect
Figure 3.33: Diagram of main elements‘ effect on Rech


16
Figure 3.32 is a general diagram of
the splitting tensile strength Rech versus
cement ratio and age. At Day 14, the
splitting tensile strength of XC
reinforced with 6-8% cement and that of
XD reinforced with 4-8% cement
exceeds 0.4-0.45Mpa, qualified to be
used for the upper roadbase. Cement
reinforced XT only applies to the road
Figure 3.34: General diagram of Rech
sub-base.
in cement reinforced XT, XC and XD
3.3.5.3. Analysis of elastic modulus (E)
Similarly conducted as desribed above, the elastic modulus E of cement
reinforced XT, XC and XD is depicted in Figure 3.35. Its changing rule is similar
to that of Rn and Rech.

a) Main elements‘ effect
b) Interactive effect
Figure 3.35: Diagram of main elements‘ effect on E

Figure 3.32 is a general diagram
of the elastic modulus E versus
cement ratio and age. At Day 14, the

E of XT reinforced with 8% cement
can reach the threshold of 600800Mpa, applicable to the roadbase
whereas XT of other cement ratios
can only be used for road sub-base
layers. The E of both cement
reinforced XC and XD reaches the
threshold of 600-800MPa, so they
Figure 3.36: General diagram of E in
can be used for roadbase.
cement reinforced XT, XC and XD
3.4. Conlusions of Chapter 3
(1) Having determined the technical specifications of Rn, Rech and E of steel


17

(2)

(3)

slag aggregate, steel slag-fine sand aggregate and steel slag-stone dust
aggregate, all cement reinforced; and established the regression equations;
Having proved that the technical specifications of steel slag-stone dust
aggregate and steel slag-fine sand aggregate are higher than those of ordinary
steel slag aggregate reinforced with the same cement content. Of all the
mixtures, cement reinforced steel slag-stone dust aggregate has the highest
technical specifications;
A suitable cement ratio (by mixture mass) of 4-6% is recommended.

FIELD EXPERIMENTS ON USE OF STEEL SLAG FOR ROADBASE AND

PROPOSAL OF PAVEMENT STRUCTURES USING STEEL SLAG
4.1.1. General informations of the test section
The test section lies on

National Highway 55, Ba
Ria-Vung Tau province.
The test section belongs to
an existing road that has the
pavement structure from top
to bottom as follows: The
asphalt
concrete
fine
grain layer is 4cm thick,
the asphalt concrete coarse
grain layer is 6cm thick,
the macadam aggregate
layer is 20cm thick and the

Figure 4.3 Pavement failures on National Highway
55 before removal for experiment

Figure 4.4: Pavement structure
of section 1

Figure 4.4: Pavement structure
of section 1

subgrade is made of laterite aggregate (CPSĐ).
4.1.2. Design of the test section

18
For the purpose of evaluation and comparison between the steel slag
aggregate and the macadam aggregate used in roadbase construction, the test
section is divided into 2 subsections of two pavement structures:

Figure 4.7: Layout of structures on the test
section

Figure 4.8 Testing conducted on the test

section
4.1.3. Testing results on the test section
4.1.3.1. Testing results conducted in October 2013
 Density (density) (K)
 Mean of density of the laterite aggregate subgrade: K= 0.987
 Mean of density of the macadam aggregate base: K=0.985
 Mean of density of the steel slag aggregate base: K =0.954
 Field elastic modulus (Edh):
 Mean of field elastic modulus of the laterite aggregate subgrade:
Edh=79.5 MPa;
 Mean of field elastic modulus of the steel slag aggregate base:
Edh=180.3 MPa;
 Mean of field elastic modulus of the macadam aggregate base:
Edh=192.5 MPa;
 Mean of field elastic modulus of asphalt concrete surface on the steel
slag aggregate base: Edh=198.6 Mpa;
 Mean of field elastic modulus of asphalt concrete surface on the
macadam aggregate base: Edh=205.4 MPa;

 Flatness of asphalt concrete pavement
Flatness of the pavement is measured by a 3 meter straight ruler according
to TCVN 8864-2011, providing below results:
- On the pavement with steel slag base: 76.2% of the gaps between the ruler
and the surface does not exceed 3mm and those of 3-5 mm wide account for
23.8%. As the result, flatness of such pavement is regarded very high as per
the current standards.
- On the pavement with macadam aggregate base: 79.4 % of the gaps between
the ruler and the surface does not exceed 3mm and those of 3-5 mm wide
account for 20.6%. As the result, flatness of such pavement is regarded very


19
high as per the current standards.
4.1.3.2. Testing results of the test section after 5 years of exploitation as of
December 2018
 Field elastic modulus (Edh)
- Mean of field elastic modulus of asphalt concrete surface on the steel slag
aggregate base: Edh=210.2 MPa;
- Mean of field elastic modulus of asphalt concrete surface on the macadam
aggregate base: Edh=200.8 MPa;
 Flatness of asphalt concrete pavement
- On the pavement with steel slag base: 71.4% of the gaps between the ruler
and the surface does not exceed 3mm and those of 3-5 mm wide account for
28.6%. As the result, flatness of such pavement is regarded very high as per
the current standards.
- On the pavement with macadam aggregate base: 73.0 % of the gaps between
the ruler and the surface does not exceed 3mm and those of 3 -5 mm wide
account for 27.0%. As the result, flatness of such pavement is regarded very
high as per the current standards.

4.1.4. Analyzing and evaluating the testing results of the test section
4.1.4.1. Statistical processing of the density results

Figure 4.10: Diagram of the density
results

Figure 4.12: Diagram of the field elastic
modulus results

4.1.4.2. Statistical processing of the field elastic modulus
The diagram of the field elastic modulus results of the laterite aggregate
subgrade, the steel slag aggregate base and the macadam aggregate base depicted in
Figure 4.12 shows that these aggregate base layers significantly increase the elastic
modulus of the pavement structure.
Caculation based on Chart 22TCN 211-06 has determined that the elastic
modulus of the steel slag aggregate base is 326MPa and that of the macadam
aggregate base is 362MPa. These values serve as the basis for the recommended
elastic modulus of the steel slag aggregate.


20

Figure 4.13: Elastic modulus on asphalt
concrete pavement in Oct. 2013

Figure 4.15: Elastic modulus on asphalt
concrete pavement in Dec. 2018

Figure 4.13 depicting the elastic modulus on asphalt concrete pavement
recorded in October 2013 shows that mean of elastic modulus on the steel slag base

reached 198.6Mpa, which is lower than that of 205.6MPa on the macadam
aggregate base but makes no significant difference.
Figure 4.15 depicting the elastic modulus on asphalt concrete pavement
recorded in December 2018 shows that after 5 years in use, mean of elastic modulus
on the steel slag base reached 210.76 Mpa, which is lower than that of 200.2 MPa
on the macadam aggregate base but makes no significant difference, yet statistically
significant as per standard 2-Sample t-Test and coefficient p-value=0.199>0.05.
4.1.5. Evaluation and remarks
The results of field testing on the test section have demonstrated that
- Under the same compacting, the density of the macadam aggregate base is higher
than that of the steel slag base;
- With the roadbase of the same thickness, the subgrade of the same strength
and under the same construction conditions, there is a little diffrence between
the elastic modulus recorded on the macadam aggregate base and that on the
steel slag base;
- After 5 ye ars of exploitation, the elastic modulus does not decrease, the
flatness of pavement with steel slag base reaches the limit, the road surface is
stable and still well exploited without any sign of damage.
4.2. Proposing pavement structures using steel slag
The reseach and testing results in lab and on site pressented in Chapter 2,
Chapter 3 and earlier Chapter 4 have proved that steel slag can be used as aggregate
in roadbase construction. Hereinafter, the doctoral candidate continued
investigating the scientific fundamentals and practices in order to propose typical
pavement structures using steel slag, which ensure the technical requirements,
reduce impacts on the environment and save resources.
4.2.1. Proposed pavement structures
4.2.1.1. Pavement structures for rural roads


21

Table 4.16 Pavement structures for rural roads
Parameters
Structure

KC1

Subgrade

KC2

Subgrade

KC3

Materials for each layer
Cement concrete with stone 1x2,
#>30Mpa, or
Cement concrete with steel slag,
#>30MPa
Flatness making layer
Steel slag + fine sand reinforced
with 6% cement, or
Steel slag + stone dust reinforced
with 4-6% cement
Steel slag reinforced with 4-6%
cement, or
Steel slag aggregate
Subgrade
Compacted sphalt concrete 12.5mm
Compacted asphalt concrete 19mm

Asphalated with 1 or 2 layers as per
TCVN 8863:201
Steel slag + fine sand reinforced
with 6% cement, or
Steel slag + stone dust reinforced
with 4-6% cement, or
Steel slag aggregate
Steel slag reinforced with 4-6%
cement; or
Steel slag aggregate
Subgrade
Asphalated with 3 layers as per
TCVN 8863:2011
Steel slag + fine sand reinforced
with 6% cement, or
Steel slag + stone dust reinforced
with 4-6% cement, or
Steel slag aggregate
Steel slag aggregate

Thickness
in cm
18  22
13
16  18

14  18

45
67

1.52.5

14  18

15  30

3.03.5

14  18
15  30

Subgrade

Subgrade

KC4

Subgrade

Cement concrete with stone 1x2,
#25-30Mpa, or
Cement concrete with steel slag,
#25-30MPa
Flatness making layer
Steel slag + fine sand reinforced
with 6% cement, or
Steel slag + stone dust reinforced

18  20
13

16  18

Scope of application

The
design
follows
230/QD-BGTVT.
The traffic flow is
designed (Nn) of 100 
200 vehicles/day&night.
Applicable to roads with
heavy vehicles (the axle is
more than 6000 Kg)
exceeding 10 %.

The
design
follows
Decision
230/QDBGTVT.
The traffic flow is
designed (Nn) of 100 
200 vehicles/day&night.
Applicable to roads with
heavy vehicles (the axle is
more than 6000 Kg)
exceeding 10 %.

The

design
follows
Decision
230/QDBGTVT.
The traffic flow is
designed (Nn) of 100 
200 vehicles/day&night.
Applicable to roads with
heavy vehicles (the axle is
more than 6000 Kg)
exceeding 10 %.
The
design
follows
Decision
230/QDBGTVT.
The traffic flow is
designed (Nn) of 50  100
vehicles/day&night.
Applicable to roads with
heavy vehicles (the axle is


22
Parameters
Structure

Materials for each layer

Thickness

in cm

with 4-6% cement

KC5

Subgrade

Steel slag aggregate
Subgrade
Cement concrete with stone 1x2,
#25Mpa, or
Cement concrete with steel slag,
#25MPa
Flatness making layer
Steel slag + fine sand reinforced
with 6% cement, or
Steel slag + stone dust reinforced
with 4-6% cement
Steel slag aggregate
Subgrade

15  18

16  18
13
14  16
14  16

Scope of application

more than 6000
exceeding 10 %.

Kg)

The
design
follows
Decision
230/QDBGTVT.
The traffic flow is
designed (Nn) lower than
50 vehicles per day and
night.
Applicable to roads with
heavy vehicles (the axle is
more than 6000 Kg)
exceeding 10 %.

4.2.1.2. Pavement structures for automobile roads
Table 4.17: Pavement structures for automobile roads
Parameters
Structure
KC6

Subgrade

KC7

Subgrade

Materials for each layer
Compacted asphalt concrete 12.5mm
Compacted asphalt concrete 19mm
Asphalated with 1 or 2 layers as per
TCVN 8863:201
Steel slag + fine sand reinforced with
6% cement, or
Steel slag + stone dust reinforced with
4-6% cement
Steel slag reinforced with 4-6%
cement, or
Steel slag aggregate
Subgrade
Cement concrete, # fr=4.5  5.0 Mpa,or
Cement concrete + steel slag, # fr=4.5
 5.0 Mpa
Flatness making layer
Steel slag + fine sand reinforced with
6% cement, or
Steel slag + stone dust reinforced with
4-6% cement
Steel slag reinforced with 4-6%
cement, or
Steel slag aggregate
Subgrade

Thickness
in cm
56

78
1.52.5
15  20

Scope of application
For pavement of high
grade A1.
The design follows
22TCN 211-06 or
22TCN 274-01.
The elastic modulus is
required of 140  160
Mpa.

16  35

20  25

13
16  25

15  30

The design follows
Decision
230/QDBGTVT.
Applicable to heavy
vehicles and lighter
means.

23
4.2.1.3. Pavement structures for motorways and roads under heavy load
Pavement structures applied for motorways and roads under heavy load are
given in Table 4.1. Steel slag aggregate serves only the subbase.
Table 4.1. Pavement structures for motorways
Parameters
Structures
KC8

Materials for each layer
Sanding layer
Polymer asphalt concrete
12.5mm/SMA
Compacted asphalt concrete 19mm
ATB25 layer
SAMI layer
Steel slag + stone dust reinforced with
4-6% cement
Steel slag + fine sand reinforced with
4-6% cement
Steel slag reinforced with 4-6%
cement, or
Steel slag aggregate
Subgrade

Thickness in
cm
2.2
4

67
8  10
2
15  18

Scope of application
For pavement of high
grade A1.
The design follows
22TCN 211-06 or
22TCN 274-01.
The elastic modulus
is required of 180
Mpa.

16  20
16  30

4.2.2. Technology for construction and exploitation of pavement using steel slag
4.2.2.1. Construction technology
It is recommended to use machinery for construction of steel slag layers.
Reinforced materials are mixed at a batching plant. Steel slag aggregate is scattered
by a spreader. Compaction should ensure the required density. There should be
solutions to reduce cracking of the asphalt concrete surface by SAMI layer or timely
cutting. For the steel slag aggregate base, the technology for construction and
acceptance is proposed similar to that for the maccadam aggregate base.
4.2.2.2. Exploitation technology
The technology for exploitation and maintenance of pavement using steel slag
does not differ from that of the traditional pavements in current use locally.
4.3. Conlusions of Chapter 4

(1) Pavement with steel slag aggregate base has been designed, constructed and
evaluated after 5 years of exploitation, and compared with pavement with
macadam aggregate base. The field experiment results show that the steel
slag aggregate base is similar to the macadam aggregate base;
(2)
8 pavement structures using steel slag with ensured technical requirements
have been proposed;
(3)
Parameters of steel slag and cement-reinforced steel slag have been
determined.