-
Fistri, M., Strineka, A., Roskovic, R.: Lastnosti agregata iz
jeklarske lindre in asfaltnega betona iz jeklarske lindre
Properties of steel slag aggregate and steel slag asphalt
concrete
mr.sc. Mladen Fistri, dipl.ing. dr.sc. Andrea Strineka,
dipl.ing. dr.sc. Ruica Roskovic, dipl.ing.
Institute IGH, Laboratory IGH, Zagreb, Croatia
Abstract
Ferrous slags (blast furnace slag, steel slag, ferro-alloy,
etc.) are the industrial by-products from a greatest interest to
the pavement construction industry, given their wide avail-ability
and scope of uses. Above that, the production of aggregate from
slag instead from rock would decrease the amount of raw material
extraction and enable further environmental benefit since less
industrial by-products would be disposed in landfills.
Until the regulations for construction products according to EU
Directives didnt get in force in Croatia, there were no technical
requirements or specifications for the evaluation of possible use
of the slag aggregates in road construction. Therefore there is no
much experience in Croatia in the application of the slag aggregate
in bituminous mixtures and the practical application is rather in
the research phase.
In this paper testing results of one type of steel slag
aggregate produced in Croatia are presented, as well as results of
the asphalt produced from 75 % of steel slag aggregate and 25 % of
limestone rock aggregate. Analysis of results showed that the
asphalt produced with the steel slag aggregate has good resistance
to permanent deformation, high stability with good flow properties
and high stiffness modulus.
Povzetek
elezne lindre (plavna lindra, jeklarska lindra, elezova zlitina
itd.) so industrijski stranski proizvodi, ki so zelo zanimivi za
gradnjo zgornjega ustroja, ker so zelo dostopni in imajo iroko
podroje uporabe. Poleg tega bi proizvodnja agregata iz lindre
namesto iz kamna zmanj-ala obseg pridobivanja surovin in omogoila
dodatne okoljske koristi, ker bi se na odlagaliih zmanjala koliina
industrijskih stranskih proizvodov.
Do uveljavitve predpisov o gradbenih proizvodih v skladu z
direktivami EU na Hrvakem ni bilo tehninih zahtev ali specifikacij
za oceno morebitne uporabe agregatov iz lindre pri gradnji cest.
Zato na Hrvakem ni veliko izkuenj pri uporabi agregata iz lindre v
bitumenskih zmeseh, praktina uporaba pa je e v fazi raziskav.
V tem prispevku so predstavljeni rezultati preskuanja vrste
agregata iz jeklarske lindre, proizvedenega na Hrvakem, in
rezultati asfalta, izdelanega iz 75 odstotkov agregata iz jeklarske
lindre in 25 odstotkov agregata iz apnenca. Analiza rezultatov je
pokazala, da ima asfalt, izde-lan iz agregata jeklarske lindre,
dobro odpornost na stalne deformacije, visoko stabilnost z dobrimi
prometnimi lastnostmi in modulom visoke togosti.
-
Fistri, M., Strineka, A., Roskovic, R.: Properties of steel slab
aggregate and steel slag asphalt concrete
10. SLOVENSKI KONGRES O CESTAH IN PROMETU, Portoro, 20. 22.
oktobra 2010
1 Introduction Ferrous slags are the industrial by-
products coming from metallurgical process of iron production
(blast furnace slag) or steel production (steel slag) which is,
because of its favourable physical and mechanical proper-ties,
almost fully used in various branches of industry. If slag is used
as raw material, it is no longer necessary to store it on
industrial waste landfill sites, and lesser quantities of mineral
raw materials need to be extracted.
Slags are mostly used in the manufacture of building materials,
such as the road con-struction aggregate, concrete, railway
ballast, cement, mineral wool, etc. It is interesting to note that
even the old Romans used slag from furnaces in the construction of
Roman roads in the Sussex District in England [1]. In the USA slag
is used from the first half of the 19th century as road
construction material, from the second half of the 19th century as
railway ballast and in cement industry, and from the beginning of
the 20th century as aggregate for bituminous mixtures [2].
Nowadays, according to the US Geologi-cal Survey data [3], 11.6
million tons of blast furnace slag was manufactured in the US in
2006. 35.7 % of this quantity was used in cement industry, and 34.3
% in road construc-tion. In the same year, out of the total of 8.7
million tons of steel slag produced, 8.2 % was used in cement
industry, and as many as 63.1 % in the production of road
construction materials.
As per data [4] provided by the European slag association
(EUROSLAG), about 25 million tons of blast furnace slag was
pro-duced in Europe in 2004. Out of this quantity 64.0 % was used
in cement industry, and 32.6 % in the production of road
construction materials. In the same year 15 million tons of steel
slag was produced. Only 1 % of that quantity was used in cement
industry, while 45 % was used in road construction (em-bankments,
loose base courses, asphalt lay-
ers). The possibility of using water cooled
steel slag to obtain a sized aggregate, suitable for asphalt
wearing course production, is studied in this paper. For that
purpose, suit-ability of slag as aggregate was tested in laboratory
and the asphalt mix type AC 11, with 75% of slag and 25% of stone
aggregate, was designed. According to this mix design asphalt plant
was adjusted and, finally, the asphalt was produced and placed as
wearing course at a test section.
2 Test results 2.1 Test results of steel slag
aggregate To assess whether slag is suitable for use
as aggregate in asphalt mixes, the laboratory conducted slag
testing in accordance with HRN EN 13043, Aggregates for bituminous
mixtures and surface treatments for roads, airfields and other
trafficked areas [5].
This standard defines requirements for aggregate, and hence for
slag, with categories according to individual aggregate
properties.
Test results for slag as aggregate, and relevant categories for
individual properties, are presented in Tables 1 to 10. Tests shown
in Tables 1 to 9 were conducted in the Stone & Aggregate
Laboratory of Institute IGH, while the testing shown in Table 10
was made in the Stone & Aggregate Laboratory of Slovenian
National Building and Civil Engi-neering Institute. 2.1.1
Geometrical properties of
steel slag aggregate Although requirements and categories
for aggregate grading and fines content are specified in HRN EN
13043, these properties (although tested) were not analyzed in this
paper as they are dominantly dependent on the technological process
of crushing, screen-ing, and dedusting.
Table 1. Particle shape of aggregates flakiness index, EN 933-3
[5] and shape index, EN 933-4 [6]
Overall flakiness index Category Shape index Category Aggregate
size (mm) FI FI SI SI
4/8 4 FI10 1 SI15
8/16 2 FI10 3 SI15
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Fistri, M., Strineka, A., Roskovic, R.: Properties of steel slab
aggregate and steel slag asphalt concrete
10. SLOVENSKI KONGRES O CESTAH IN PROMETU, Portoro, 20. 22.
oktobra 2010
Table 2. Determination of the flow coefficient of fine
aggregates, EN 933-6 [7]
Aggregate size (mm)
Flow coefficient of aggregates Ecs (s)
Category Ecs
0/4 18 Ecs38
2.1.2 Physical properties of steel slag aggregate
Table 3. Determination of resistance to wear (micro Deval), EN
1097-1 [8]
Micro-Deval koeficijent
Mean value Category Aggregate size/
/test type Particle size
fractions DEM DEM DEM
7,8 8/16 mm/ /wet
10/11,2 mm: 30-40 %
11,2/14 mm: 70-30 % 7,3
8 10DEM
Table 4. Resistance to fragmentation by the Los Angeles test
method, EN 1097-2 [9]
Los Angeles coefficient Category Aggregate size (mm) Particle
size fractions
LA LA 10/11,2 mm: 30 %
8/16 11,2/14 mm:70 %
13 LA15
Table 5. Particle density and water absorption, EN 1097-6
(Pyknometer method) [10]
Particle density (Mg/m3)
Water absorption (%) Aggregate size (mm)
ssd rd a 24WA 0/4 3,49 3,41 3,69 2,2 4/8 3,65 3,59 3,82 1,7
8/16 3,73 3,68 3,88 1,5
Table 6. Determination of the polished stone value, EN 1097-8
[11]
Mean polished stone value PSV
Category PSV
70 PSV68
2.1.3 Thermal and weathering properties of steel slag
aggregate
Table 7. Determination of resistance to freezing and thawing
according to EN 1367-1 [12] and by mag-nesium sulfate test
according to EN 1367-2 [13]
Magnesium sulphate crystallization method Freeze thaw test
method Particle size
fraction Mean value Category Mass loss Category
(mm) MS MS (%) F 8/16 1 MS18 0,4 F1
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Fistri, M., Strineka, A., Roskovic, R.: Properties of steel slab
aggregate and steel slag asphalt concrete
10. SLOVENSKI KONGRES O CESTAH IN PROMETU, Portoro, 20. 22.
oktobra 2010
Table 8. Determination of resistance to thermal shock, EN 1367-5
[14]
Change in resistance to fragmentation by Los Angeles test method
Particle size
fraction (mm) Mass loss LA1 before heating
LA2 after thermal
shock
Loss in strength (VLA= LA2-LA1)
10-14 mm 0,4 % 12,8 14,1 1,3
Table 9. Determination of the affinity between aggregate (slag)
and bitumen, EN 12697-11 [21]
Degree of bitumen coverage (%) Particle size fraction (mm)
after 6 h after 24 h 8/11 95 90
2.1.3 Chemical properties of steel slag aggregate
Table 10. Volume stability of steel slag aggregate, EN 1744-1,
19.3 [15]
Type of steel slag Expansion (% v/v) Category of volume
stability
V Steel slag cooled by water 2,2 V3,5
2.2 Test results of asphalt with steel slag aggregates
Test of the asphalt mix samples was conducted and initial mix
design was devel-oped in the Asphalt Laboratory of INSTI-TUTE IGH
for the asphalt mix type AC 11 with steel slag. The following
constituents were used in the asphalt mix production: water-cooled
steel slag, crushed rock aggre-gate of carbonate composition and
sedimen-tary origin from Tounj Quarry (0/4 mm
aggregate size), and "Japra" mineral filler of carbonate
composition. The road-construction bitumen type 50/70 was used as
binder. Proportions of individual mineral components in the
designed asphalt type AB 11 (slag) are shown in Table 11. The
designed proportion of bitumen was 5,3 [%(m/m)].
The asphalt plant was adjusted for pro-duction with these
materials, and the asphalt mix was produced based on the mix
design. This asphalt mix was placed at the test section in August
2009.
Table 11. Mineral material fractions in the design asphalt
mix
Mineral material Fraction Quantity in mix [% (m/m)] JAPRA filler
3,1 TOUNJ 0 - 4 25,5
TROSKA 0 - 4 25,5 TROSKA 4 - 8 26,4 TROSKA 8 - 11 19,5
2.2.1 Testing of asphalt mix-tures
The asphalt mix samples taken at the as-phalt plant during
production were submitted to the following laboratory testing:
soluble binder content (EN 12697-1) [16];
particle size distribution (EN 12697-2) [17];
maximum density (EN 12697-5) [18]; bulk density of bituminous
specimens
(EN 12697-6) [19]; air voids content, voids in the mineral
aggregate, voids in the mineral aggreg-
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Fistri, M., Strineka, A., Roskovic, R.: Properties of steel slab
aggregate and steel slag asphalt concrete
10. SLOVENSKI KONGRES O CESTAH IN PROMETU, Portoro, 20. 22.
oktobra 2010
gate filled with binder (EN 12697-8) [20];
water sensitivity (EN 12697-12 - Method A Indirect tensile
strength) [22];
indirect tensile strength (EN 12697-23) [24];
stiffness (EN 12697-26 Annex C) [25];
stability and flow (EN 12697-34) [27]. Test results for asphalt
mixtures are
shown in Tables 12 to 15.
!"#$
Figure 1. Particle size distribution of sampled mineral
mixture
Table 12. Typical properties of steel slag asphalt mix
Soluble binder content [% (m/m)] 5,1 Bulk density of bituminous
specimens [kg/m] 2723 Maximum density [kg/m] 2894 Void content [%
(v/v)] 5,9 Voids in the mineral aggregate [% (v/v)] 19,5 Voids in
the mineral aggreggate filled with binder [% (v/v)] 69,7
Test specimens for determination of wa-ter susceptibility of
bituminous specimens were prepared using Marshall compactor (EN
12697-30) with 2 x 35 blows.
Half of total number of specimens were conditioned for 72 hours
in temperature
chamber at 25 C, while the remaining specimens were stored in
water for 72 hours at the temperature of 40 C. The tensile strength
was determined at 25 C.
Table 13. Test results of water sensitivity
Indirect tensile strength of dry specimens
Indirect tensile strength of wet specimens Indirect tensile
strength ratio
[MPa] [MPa] [%] 1,6 1,3 80,0
The indirect tensile strength testing was conducted at two
testing temperatures: 25 C and 5 C. Test specimens for this testing
were
prepared by 2 x 50 blows, using Marshall compactor.
-
Fistri, M., Strineka, A., Roskovic, R.: Properties of steel slab
aggregate and steel slag asphalt concrete
10. SLOVENSKI KONGRES O CESTAH IN PROMETU, Portoro, 20. 22.
oktobra 2010
Table 14. Test results of indirect tensile strenght and
stiffness modulus
Indirect tensile strength at 5 C Indirect tensile strength at 25
C Stiffness modulus
[MPa] [MPa] [MPa] 4,0 1,8 7128
The stiffness modulus was determined by testing indirect tensile
strength according to HRN EN 12697-26. For this testing, six
specimens were prepared for each mix using Marshall compactor (2 x
50 blows). The testing was conducted at 20 C. The asphalt mix test
results are presented in Tables 12 to 15.
The water susceptibility testing of bitu-men specimens was
conducted according to EN 12697-12 by tensile strength
measure-ment. Twelve specimens were prepared for
testing with 2 x 35 blows using Marshall compactor. Out of the
total of twelve samples, six were stored for 72 hours in
temperature chamber at 25 C, while the remaining six specimens were
stored in water for 72 hours at the temperature of 40 C. The
tensile strength was determined at 25 C.
The indirect tensile strength testing was conducted at two
testing temperatures: 25 C and 5 C. Twelve specimens were prepared
for this testing by 2 x 50 blows, using Mar-shall compactor.
Figure 2 Testing head for indirect tensile strength test
Figure 3 Apparatus for stiffness modulus test
Determination of the stability, flow and the Marshall Quotient
of Marshall specimens, was performed according to EN 12697-34.
Table 15. Marshall test
Property Unit AB 11 (slag) Stability kN 15,2
Flow mm 2,5 Marshall quotient kN/mm 6,1
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Fistri, M., Strineka, A., Roskovic, R.: Properties of steel slab
aggregate and steel slag asphalt concrete
10. SLOVENSKI KONGRES O CESTAH IN PROMETU, Portoro, 20. 22.
oktobra 2010
2.2.2 Testing properties of the placed asphalt layer
In the IGH Asphalt laboratory the fol-lowing tests of the placed
asphalt layer were conducted:
resistance to permanent deformation by wheel - tracking test
[23];
compaction degree; thickness [28].
To enable the above testing, 200 and 100 mm samples were
extracted by drilling from the wearing course at the test section.
Wheel tracking was performed on samples 200 mm in dia. using the
Procedure B at ambient air and at the temperature of 60C. The test
result
is the rutting depth after the test specimen was subjected to
20,000 passes of wheels.
Test conditions for wheel tracking: wheel load: 700 N; total
distance of travel of tyre wheel
across the surface of test specimen: 230 mm;
frequency of loading: 26,5 cycles per minute;
test temperature: 60 C; number of load cycles: 10 000.
The compaction degree and thickness testing was performed on
specimens 100 mm in diameter. Test results obtained in this testing
are shown in Tables 16 and 17.
Table 16. Wheel tracking test results
PROPERTY AB 11 (SLAG) Mean wheel-tracking slope, WTSAIR mm/1000
cycles 0,09 Mean proportional rut depth, PRDAIR % 5,7 Mean rut
depth, RDAIR mm 2,7
rut depth vs. number of passes
0
0,5
1
1,5
2
2,5
3
3,5
4
4,5
5
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000
13000 14000 15000 16000 17000 18000 19000 20000
Number of passes
Rut d
epth
[m
m]
AB 11 (SLAG)
Figure 2 Wheel tracking test results
Table 17. Results obtained by testing compaction degree and
thickness of the placed asphalt layer
PROPERTY AC 11 (SLAG) Bulk density (kg/m3) 2676 Compaction
degree (%) 98,2 Layer thickness (mm) 45,4
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Fistri, M., Strineka, A., Roskovic, R.: Properties of steel slab
aggregate and steel slag asphalt concrete
10. SLOVENSKI KONGRES O CESTAH IN PROMETU, Portoro, 20. 22.
oktobra 2010
3 Analysis of results 3.1 Results obtained by steel
slag aggregate testing After analysis of laboratory test
results
for the pre-crushed water cooled steel slag, it was established
that:
geometrical properties with respect to shape index and flatness
index meet criteria for highest categories (FI10 ; SI 15),
resistance of slag to wear in wet state complies with
requirements for the highest category (MDE10),
crushing resistance by Los Angeles method meet requirements for
the highest category (LA15) and, after the heat shock, the decrease
in strength is low, i.e. 1.3 (the value determined dur-ing the
testing is 14.1 and is suitable for the highest category),
polishing stone value is also adequate for the highest category
(PSV68),
density values are high, which was to be expected considering
the origin of the aggregate,
on the tested fractions, the water ab-sorption was higher than 1
%,
mass losses during testing by the mag-nesium sulphate method and
the freez-ing/thawing method are very small, and the results
obtained meet the highest-category requirements for the durability
of aggregates,
the volume of slag is stable and, ac-cording to the expansion
value, the slag meets the highest volume stability
re-quirements,
the adhesion of bitumen binder, tested by method A, is 95 %
after 6 hours, and 90 % after 24 hours.
3.2 Results obtained by test-ing asphalt containing the steel
slag aggregate
According to HRN EN 13108 - 1 (Bitu-minous mixes - Material
specifications - Part 1: Asphalt concrete), the mix AC 11 with
steel slag can be classified, based on some of the tested
properties, into the following cate-gories as shown in Table
18:
Table 18. Categories for mix AC 11 with steel slag
Test property Category Total number of categories for selected
property according to
EN 13108 - 1 Water sensitivity expressed by indirect tensile
strength ratio ITSR80 2 of 5
Stiffness Smin7000 6 of 14
Maximum wheel tracking slope WTSAIR 0,10 4 of 12
Maximum proportional rut depth PRDAIR 5,0 5 of 8
4 Conclusion The results obtained by aggregate testing
shows that the aggregate produced from water-cooled steel slag
meets criteria for the use in asphalt mixes. When compared with
aggregates produced from igneous rocks of silicate composition that
are used in asphalt mixes on motorways and roads belonging to
highest traffic load categories, it can be concluded that most
properties of the slag submitted to this testing are equally good.
The resistance to polishing is even much better when compared to
silicate rocks. Only the water absorption value is somewhat
higher
when compared to silicate rocks that are used for aggregate
production.
The test results of the asphalt mix and placed asphalt layer
shows that asphalt pro-duced with steel slag aggregate has good
resistance to permanent deformation, high stability with good flow
properties and high stiffness modulus. Samples also show high
stabilities, with good flow properties. The higher stability and
stiffness modulus of steel slag asphalt mix can be used to design
thinner asphalt layers. Because good resistance to polishing of
steel slag particles, it can be expected that asphalt with steel
slag will have very good skid resistance value (SRV), once
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Fistri, M., Strineka, A., Roskovic, R.: Properties of steel slab
aggregate and steel slag asphalt concrete
10. SLOVENSKI KONGRES O CESTAH IN PROMETU, Portoro, 20. 22.
oktobra 2010
the bitumen film will be removed from its surface.
References
[1] Emery, J.: Steel Slag Utilization in Asphalt Mixes, National
Slag Association, MF 186-1, www.nationalslagassoc.org
[2] Lewis, D.W.: Properties and Uses of Iron and Steel Slags.
National Slag Association, MF 182-6, www.nationalslagassoc.org
[3] van Oss, H. G.: Slag Iron and Steel, U.S. Geological Survey
2007 Minerals Yearbook, minerals.usgs.gov
[4] The European Slag Association: Legal Status of Slags,
EUROSLAG, Position paper, www.euroslag.org
[5] EN 13043 Aggregates for bituminous mixtures and surface
treatments for roads, air-fields and other trafficked areas
[6] EN 933-4:2008 Tests for geometrical proper-ties of
aggregates -- Part 4: Determination of particle shape -- Shape
index
[7] EN 933-6:2006 Tests for geometrical proper-ties of
aggregates -- Part 6: Assessment of sur-face characteristics --
Flow coefficient of ag-gregates
[8] EN 1097-1:2004 Tests for mechanical and physical properties
of aggregates -- Part 1: De-termination of the resistance to wear
(micro-Deval)
[9] EN 1097-2:2007 Tests for mechanical and physical properties
of aggregates -- Part 2: Methods for the determination of
resistance to fragmentation
[10] EN 1097-6:2007 Tests for mechanical and physical properties
of aggregates -- Part 6: Determination of particle density and
water absorption
[11] EN 1097-8:2009 Tests for mechanical and physical properties
of aggregates -- Part 8: Determination of the polished stone
value
[12] EN 1367-1:2008 Tests for thermal and weathering properties
of aggregates -- Part 1: Determination of resistance to freezing
and thawing
[13] EN 1367-2:2004 Tests for thermal and weathering properties
of aggregates -- Part 2: Magnesium sulfate test
[14] EN 1367-5:2004 Tests for thermal and weathering properties
of aggregates -- Part 5: Determination of resistance to thermal
shock
[15] EN 1744-1:2004 Tests for chemical properties of aggregates
-- Part 1: Chemical analysis
[16] EN 12697-1:2007 Bituminous mixtures -- Test methods for hot
mix asphalt -- Part 1: Soluble binder content
[17] EN 12697-2:2008 Bituminous mixtures -- Test method for hot
mix asphalt -- Part 2: De-termination of particle size
distribution
[18] EN 12697-5:2009 Bituminous mixtures -- Test methods for hot
mix asphalt -- Part 5: Determination of the maximum density
[19] EN 12697-6:2008 Bituminous mixtures -- Test methods for hot
mix asphalt -- Part 6: Determination of bulk density of bituminous
specimens
[20] EN 12697-8:2003 Bituminous mixtures -- Test methods for hot
mix asphalt -- Part 8: Determination of void characteristics of
bitu-minous specimens
[21] EN 12697-11:2008 Bituminous mixtures -- Test methods for
hot mix asphalt -- Part 11: Determination of the affinity between
aggre-gate and bitumen
[22] EN 12697-12:2008 Bituminous mixtures -- Test methods for
hot mix asphalt -- Part 12: Determination of the water sensitivity
of bitu-minous specimens
[23] EN 12697-22:2008 Bituminous mixtures -- Test methods for
hot mix asphalt -- Part 22: Wheel tracking
[24] EN 12697-23:2004 Bituminous mixtures -- Test methods for
hot mix asphalt -- Part 23: Determination of the indirect tensile
strength of bituminous specimens
[25] EN 12697-26:2008 Bituminous mixtures -- Test methods for
hot mix asphalt -- Part 26: Stiffness
[26] EN 12697-30:2008 Bituminous mixtures -- Test methods for
hot mix asphalt -- Part 30: Specimen preparation by impact
compactor
[27] EN 12697-34:2008 Bituminous mixtures -- Test methods for
hot mix asphalt -- Part 34: Marshall test
[28] EN 12697-36:2003 Bituminous mixtures -- Test methods for
hot mix asphalt -- Part 36: Determination of the thickness of a
bituminous pavement