Performance of asphalt concrete with dolomite sand waste and BOF steel slag aggregate/Asfaltbetonio misinio eksploatacines savybes naudojant dolomito smelio atliekas ir bazines deguonies krosnies plieno slako uzpilda/ No terauda sarniem un dolomita atsijam izgatavoto asfaltbetona sastavu ekspluatacijas ipasibas/ Dolomiidiliiva jaatmetega ja terasesulatusahju rabuga asfaltbetooni kaitumine.
Haritonovs, Viktors ; Zaumanis, Martins ; Brencis, Guntis 等
1. Introduction
During the recent years, huge quantities of technological waste,
such as steel slag and very fine crushed dolomite sand that need to be
recycled with max efficiency have accumulated in Latvia (Figs 1, 2). The
produced waste mostly remains unused in quarries occupying space and
increasing the overall technological costs. At the same time the road
building industry in the Baltic States strives to utilize the local
aggregates because the physical-mechanical characteristics of most of
the materials do not meet the normative requirements (Bulevicius et al.
2011).
The coproducts (slag) of iron and steel production have been used
commercially since 19th century. In the European Union and North America
steel slag is used in: bituminous bound materials, pipe bedding,
hydraulically bound mixtures for subbase and base, unbound mixtures for
subbase, capping, embankments and fill construction, clinker manufacture
and fertilizer and soil improvement agent (Xirouchakis, Manolakou 2011).
However, in Lat via, for commercial road construction purposes, it has
been used only for unbound mixtures.
The research has showed that production of asphalt mixtures with
high performance characteristics is possible by using steel slag
aggregate (Pasetto, Baldo 2011). However, the studies have also
indicated that, because of the high angularity and texture of the
particles, the asphalt often has poor workability. Therefore, the
application of slag may have more potential in combination with
conventional aggregates (Bagampadde et al. 1999).
The second most widespread coproduct in Latvia is the dolomite
waste sand. It has been accumulating in quarries for many years and
currently its quantity has reached several million tones. Previously, it
was used in agriculture as the lime substitute for soil treatment and in
the building industry as the quartz sand equivalent. Currently,
researchers in Latvia also offer to utilize the dolomite sand waste in
the concrete production (Korjakins et al. 2008). However, the research
on the perspective use of dolomite waste sand in production of asphalt
has received relatively little attention. For example, this material
could be used to fully or partially replace the fine and filler
portions.
The goal of this study is to examine the performance properties of
asphalt mixtures that contain different dosages of dolomite waste and
Basic Oxygen Furnace (BOF) steel slag and to compare the results with
reference asphalt mixture produced with conventional aggregates. The
testing includes determination of plastic deformations and fatigue life.
2. Materials
The following materials were used in the study: BOF slag, dolomite
waste sand, conventional aggregate (crushed dolomite and quartz sand)
and bitumen.
2.1. Aggregate tests
The Latvian law classifies BOF slag and dolomite sand waste as
non-hazardous solid materials according to the Council Directive
91/689/EEC on Hazardous Waste. The chemical analysis (Table 1) shows
that both co-products contain a prevalence of CaO and MgO but the BOF
steel slag also contains a large amount of Si[O.sub.2] and FeO.
[FIGURE 1 OMITTED
[FIGURE 2 OMITTED
The physical and mechanical properties of steel slag, dolomite
waste sand, crushed dolomite aggregate and quartz sand are summarized in
Table 2. The tests were carried out according to the European standard
(EN) test methods. The properties of BOF steel slag correspond to the
highest category of standard LVE EN 13043 Aggregates for Bituminous
Mixtures and Surface Treatments for Roads, Airfields and other
Trafficked Areas. However, because of high abrasivety of this material,
the proportion of it for wearing courses according to Latvian Road
Specifications 2010 has been restricted to 20%. The test results of
steel slag main properties show a very low flakiness index--2, excellent
mechanical strength with average Los Angeles coefficient (LA) value of
19, high frost resistance with average Magnesium Sulfate (MS) test value
of 3, low fines content--0.5% and slag expansion tests showed that the
expected swelling should be negligible (Table 2).
Dolomite waste sand test results present excellent angularity with
average flow coefficient of 33. The fines content in dolomite waste sand
is more than 10%, therefore the Latvian Road Specifications 2010 require
this material to satisfy also the requirements attributed to mineral
filler. Test results show that the fines quality is high--the material
has low methylene blue (MB) value -0.5, high carbonate content--more
than 90%, excellent Rigden air voids and Delta ring and ball tests--28
and 11 respectively.
2.2. Aggregate gradation
In total, 9 aggregate gradations were used for producing the AC 11
mixtures--5 unconventional co-product aggregate and 4 conventional
crushed dolomite and quartz sand aggregates (Table 3).
Dolomite waste sand is categorized as [G.sub.F]85, steel slag 0/5
as [G.sub.A]90 and steel slag 4/8 as [G.sub.C]90/20 according to the LVS
EN 13043. Steel slag which is categorised as 8/11 does not confirm to
any of the standard categories, because only 81.8% particles pass D
sieve (11.2 mm) while the standard requires at least 85%. The 2/5 steel
slag also does not correspond to the standard category because of high
percentage of particles passing 1.0 mm (d/2) sieve (the standard
requires < 5).
2.3. Bitumen tests
Unmodified bitumen BND 60/90 (category is defined in accordance to
Russian specifications) and SBS polymer modified bitumen PMB 45/80-55
was used for the testing. Unmodified bitumen is characterized by a pen
of 65 dmm at 25 [degrees]C, softening point is reached at 50.4
[degrees]C and the Fraas temperature is -25 [degrees]C. The SBS modified
bitumen has a pen of 59 dmm, softening point of 67.7 [degrees]C and the
Fraas temperature -16 [degrees]C. All the test results of the bitumen
BND 60/90 and PMB 50/70-53 are shown in Table 4.
[FIGURE 3 OMITTED]
[FIGURE 4 OMITTED]
3. Mix design
Dense graded AC mixtures have been designed by using conventional
and unconventional raw materials. Aggregate gradation fulfilled the
basic requirements defined in LVS EN 13108-1 Bituminous
Mixtures--Material Specifications --Part 1: Asphalt Concrete and the
complementary Latvian criteria specified in Autocelu specifikacijas 2010
[Road Specifications 2010]. The Marshall mix design procedure was used
for the determination of the optimal bitumen content for the reference
mixture, considering the mixture test results for Marshall stability and
flow, as well as the volumetric values: air voids (V), voids in mineral
aggregate (VMA) and voids filled with bitumen (VFB) (Roberts et al.
2002). Test specimens for Marshall Test had the shape of cylinder with
diameter of 101 mm and height range from 62.5 mm to 64.5 mm. All of them
were prepared in the laboratory by impact compactor according to the LVS
EN 12697-30 Bituminous Mixtures--Test Methods for Hot Mix Asphalt--Part
30: Specimen Preparation by Impact Compactor) with 2 x 50 blows of
hammer 140[degrees]C temperature.
Three different groups of mixtures were analysed:
- two reference mixtures without coproducts (with conventional and
SBS bitumen) which were used as a control;
- mixtures containing only BOF slag and dolomite waste sand;
- combination of conventional and unconventional materials.
In order to determine the potential of using unconvential
aggregates in the mixtures, the 2nd and 3rd groups of mixtures were
prepared by using only conventional bitumen. Each group of mixtures is
characterized by different bitumen contents in the range 5.4-7.0% on the
weight of the aggregate. The optimal bitumen content was determined by
optimising the volumetric characteristics and considering resistance to
deformation with wheel tracking test. This variation of bitumen content
even having similar grading curves can result in high hygroscopicity of
dolomite waste material, differences in aggregate bulk density and high
bitumen absorption of BOF steel slag material (Sivilevicius et al. 2008,
2011; Vislavicius, Sivilevicius 2013).
4. Performance evaluation
4.1. Resistance against permanent deformations
Resistance against permanent deformation was determined according
to the standard LVS EN 12697-22 Bituminous Mixtures--Test Methods for
Hot Mix Asphalt Part 22: Wheel Tracking method B (wheel tracking test
with small size device in air). This test method is designed to repeat
the stress conditions observed in the field, therefore is categorised as
simulative. The asphalt mixture resistance to permanent deformation is
assessed by the depth of the track and its increments caused by
repetitive cycles (26.5 cycles/m) under constant temperature (60
[degrees]C) (Fig. 3). The rut depths are monitored by means of two
linear variable displacement transducers (LVDTs) which measure the
vertical displacements of each of the two wheel axles independently as
rutting progresses.
Rectangular shape specimens with the base area of 305 x 305 mm were
prepared for the test by using roller compactor according to the LVS EN
12697-33 Bituminous Mixtures--Test Methods for Hot Mix Asphalt Part 33:
Specimen Prepared by Roller Compactor (Fig. 4). Thickness of the tested
specimens conforms to that of the traditional pavement surface layer--40
mm. The test assesses three parameters:
- Wheel Tracking Slope (WT[S.sub.AIR], mm/1000cycles) which is
defined as increase in the depth of wheel track per 1000 test cycles;
- Rut Depth (R[D.sub.AIR], mm) which is the accumulated permanent
deformation after 10000 cycles;
- Proportional Rut Depth (PR[D.sub.AIR], %) which is the relative
depth of wheel track after 10000 test cycles in proportion to the test
specimen thickness.
Fig. 5 reports the evolution of the loading cycles--rut depth
curves during the test conducted. The wheel tracking slope has been
calculated by using the following equation:
WT[S.sub.AIR] = [([d.sub.10000] - [d.sub.5000])]/5, (1)
where WT[S.sub.AIR] - the wheel tracking slope, mm/1000cycles;
[d.sub.5000] and [d.sub.10000] - the rut depths after 5000 and 10000
load cycles, mm.
The experimentally obtained curves illustrate asphalt as typical
visco-elastic-plastic material. The 1st phase has a decreasing wheel
tracking slope (creep rate), whereas, the 2nd has a constant wheel
tracking slope.
The requirements for wheel tracking slope in Latvia are regulated
by the requirements of Autocelu specifikacijas 2010 [Road Specifications
2010]. All of the mixtures fulfilled requirement to the category of
WT[S.sub.AIR] 0.3 for road with high traffic volume. The results are
presented in Table 5.
The largest plastic strain of 5.78 mm and the highest wheel
tracking slope of 0.29 mm in 1000 cycles appear for the reference
mixture with unmodified bitumen. The results for reference mixture with
SBS modified bitumen are only slightly better (5.05 mm to 0.28 mm/1000
cycles). The asphalt concrete mixture which was produced entirely from
coproducts shows surprisingly good resistance to permanent deformations,
having an average rut depth value of 1.54 mm and wheel tracking slope of
0.12 mm/1000 cycles. The mixture with combination of coproduct and
conventional aggregate had somewhat worse test results: rut depth value
of 3.94 mm and the wheel tracking slope of 0.19 mm/1000 cycles. The
steel slag fractions of 0/5 and 2/5 in this mixture were replaced with
dolomite filler and crushed quartz sand, because of the strength and
angularity the fine steel slag fractions which can cause excessive wear
of the asphalt production and paving equipment. In a dense graded
asphalt concrete the aggregates and bitumen both have an active role in
forming the structure. Therefore, the test results confirm that high
resistance to rutting is attained by using modified bitumen as well as
aggregates with rough surface texture which promises more aggregate
interlock and surface friction. It is also important that the
combination of steel slag with mineral aggregates allowed reducing the
bitumen content by significant 1% (from 7% to 6%). The optimisation of
the bitumen content was performed by utilization of fatigue and rutting
test results. Low bitumen amount reduces the fatigue performance, while
highly increases the rutting.
[FIGURE 5 OMITTED]
4.2. Fatigue
Fatigue properties were determined using four point bending test
device (4PB) (Fig. 6). This method consists of a cyclic bending of
prismatic specimen at a constant strain amplitude. The beams were
compacted in the laboratory by using roller compactor. They were saw cut
to the required dimensions of 50 mm wide, 50 mm high and 400 mm long.
Resistance to fatigue was determined at 20 [degrees]C and 30 Hz
according to the LVS EN 12697-24 Bituminous Mixtures--Test Methods for
Hot Mix Asphalt--Part 24: Resistance to Fatigue.
Fatigue life is defined as the number of cycles which corresponds
to 50% decrease of initial stiffness modulus. In this study the fatigue
was determined by applying half million load cycles to the beam. The
results are given in Fig. 7.
The results indicate that the mixture with BOF steel slag and
dolomite sand waste (100% coproduct) showed less resistance to fatigue
compared to results for mixture made with conventional aggregates and
combined mixture. The mix designs that include exclusively dolomite
aggregates as well as the combination of dolomite and slag in coarse
portion plus waste sand in fine aggregate portion exhibit slightly
higher fatigue life compared to other combinations. The fatigue life
exceeded 500 000 cycles for all the combinations with the exception of
100% by-product mixtures made with BND 60/90 bitumen. However, to verify
the findings more extensive laboratory research is needed.
[FIGURE 6 OMITTED]
[FIGURE 7 OMITTED]
5. Conclusions
BOF steel slag aggregates meet the Autocelu specifikacijas 2010
[Road Specifications 2010] requirements in Latvia to road construction
aggregate. Physical and mechanical properties of steel slag aggregates
are comparable with the characteristics of conventional natural
aggregate usually used in transportation infrastructure. Steel slag
aggregates have high resistance to fragmentation with the average LA
value of 19, excellent shape ([FI.sub.2]) and texture characteristics.
The values of these parameters are higher than those for conventional
dolomite and granite aggregates that are used in Latvia. The main
disadvantages of the material are high density which raise the
transportation costs and large porosity that forces to use the increased
bitumen dosage.
Dolomite sand waste fulfills the highest standard LVS EN 13043
category in terms of angularity having an average value of flow
coefficient of 33 which also satisfies the Autocelu specifikacijas 2010
[Road Specifications 2010] requirements to sand. The dolomite waste sand
has high filler content--18.6% and, therefore has to be tested for the
properties of filler. The research showed high quality of this material
having low methylene blue value (MBF0.5), high carbonate content
(C[C.sub.90]), excellent Rigden air voids ([V.sub.28/38]) and Delta ring
and ball ([[DELTA].sub.R&B] 8/25).
Mixture from 100% steel slag and dolomite waste sand that was
prepared using unmodified bitumen BND 60/90 shows high resistance to
permanent deformation WT[S.sub.AIR]0.12. However, this combination has
high optimum binder content--7%. Mixture form steel slag and dolomite
aggregate in coarse portion plus dolomite waste sand and crushed quartz
sand in the sand and filler portion had a little lower resistance to
permanent deformation (WT[S.sub.AIR]0.19) than the mixture made only
from steel slag. However, the value was significantly higher than that
for the reference mixtures made with dolomite aggregates, crushed quartz
sand and limestone filler with both conventional and SBS modified
bitumen--WT[S.sub.AIR]0.29 and WT[S.sub.AIR]0.28 respectively. This
mixture with a combination of conventional aggregate and co-products has
also significantly lower bitumen content which lowers the production
costs compared to the mixture made entirely from co-products.
The mixtures made with steel slag and local limestone in coarse
portion plus dolomite sand waste in sand and filler portions exhibit
slightly higher fatigue resistance than the conventional mixtures.
However, the mixture from 100% steel slag and dolomite waste sand shows
less resistance to fatigue.
Further analysis of the effect of using waste products should
involve research on the resistance to deformations in low and moderate
temperatures. It must also include further optimization of co-product
and conventional aggregate in order to reduce the bitumen content while
still maintaining high resistance to permanent deformation, fatigue and
thermal cracking.
Caption: Fig. 1. Unfractionated BOF slag aggregate
Caption: Fig. 2. Unused dolomite waste sand
Caption: Fig. 3. Test equipment for wheel tracking test
Caption: Fig. 4. Roller compactor
Caption: Fig. 5. Wheel tracking test curves
Caption: Fig. 6. Test equipment for fatigue test
Caption: Fig. 7. Fatigue test results
doi:10.3846/bjrbe.2013.12
Received 3 February 2012; accepted 28 February 2012
Acknowledgement
This work has been supported by the European Regional Development
Fund (ERDF) activity No. 2.1.1.1. "Atbalsts zin?tnei un
petniecibai" (support for the science and research) within the
project No.2010/0254/2DP/2.1.1.1.0/10/APIA/VIAA/015.
References
Bagampadde, U.; Al-Abdul Wahhab, H. I.; Aiban, S. A. 1999.
Optimization of Steel Slag Aggregates for Bituminous Mixes in Saudi
Arabia, Journal of Materials in Civil Engineering 11(1): 30-35.
http://dx.doi.org/10.1061/(ASCE)0899-1561(1999)11:1(30).
Bulevicius, M.; Petkevicius, K.; Zilioniene, D.; Cirba, S. 2011.
Testing of Mechanical-Physical Properties of Aggregates, Used for
Producing Asphalt Mixtures, and Statistical Analysis of Test Results,
The Baltic Journal of Road and Bridge Engineering 6(2): 115-123.
http://dx.doi.org/10.3846/bjrbe.2011.16.
Korjakins, A.; Gaidukovs, S.; Sahmenko, G.; Bajare, D.; Pizele, D.
2008. Investigation of Alternative Dolomite Filler Properties and Their
Application in Concrete Production, Scientific Journal of RTU,
Construction Science 2(9): 64-71.
Pasetto, M.; Baldo, N. 2011. Mix Design and Performance
Characterization of Bituminous Mixtures with Electric Arc Furnace Steel
Slags, in Proc. of 5th Internationa Conference "Bituminous Mixtures
and Pavements". June 1-3, 2011, Thessaloniki, Greece, 287-297.
Roberts, F.; Mohammad, L.; Wang, L. 2002. History of Hot Mix
Asphalt Mixture Design in the United States, Journal of Materials in
Civil Engineering 14(4): 279-293. http://dx.doi.org/10.1061/(ASCE)0899
1561(2002)14:4(279).
Sivilevicius, H.; Podvezko, V.; Vakriniene, S. 2011. The Use of
Constrained and Unconstrained Optimization Models in Gradation Design of
Hot Mix Asphalt Mixture, Construction and Building Materials 25(1):
115-122. http://dx.doi.org/10.1016/j.conbuildmat.2010.06.050.
Sivilevicius, H.; Vislavicius, K. 2008. Stochastic Simulation of
the Influence of Variation of Mineral Material Grading and Dose Weight
on Homogeneity of Hot Mix Asphalt, Construction and Building Materials
22(9): 2007-2014. http://dx.doi.org/10.1016/j.conbuildmat.2007.07.001.
Vislavicius, K.; Sivilevicius, H. 2013. Effect of Reclaimed Asphalt
Pavement Gradation Variation on the Homogeneity of Recycled Hot-Mix
Asphalt, Archives of Civil and Mechanical Engineering (2013).
http://dx.doi.org/10.1016/j.acme.2013.03.003.
Xirouchakis, D.; Manolakou, V. 2011. Properties of EAF Slag
Produced in Greese: a Constructional Material for Sustainable Growth, in
Proc. of 5thInternational Conference Bituminous Mixtures and Pavements.
June 1-3, 2011, Thessaloniki, Greece, 287-297.
Viktors Haritonovs (1) ([mail]), Martins Zaumanis (2), Guntis
Brencis (3), Juris Smirnovs (4)
Dept of Road and Bridge, Riga Technical University, ?zenes 16/20,
1048 Riga, Latvia E-mails: (1) viktors.haritonovs@rtu.lv; (2)
jeckabs@gmail.com; (3) guntis.brencis@rtu.lv; (4)
smirnovs@mail.bf.rtu.lv
Table 1. Chemical composition of by-products
Oxide content, %
BOF steel slag Dolomite waste sand
Oxide Content, % Oxide Content, %
CaO 30.6 CaO 31.0
MgO 18.9 MgO 17.0
Si[O.sub.2] 19.9 Si[O.sub.2] 2.5
MnO 6.3 [Na.sub.2O] 0.82
[Al.sub.2][O.sub.3] 5.0 [Al.sub.2][O.sub.3] 0.64
Ti[O.sub.2] 0.52 [K.sub.2]O 0.76
FeO 16.3 [Fe.sub.2][O.sub.3] 0.34
Table 2. Physical and mechanical characteristics of the aggregate
Physical and Standard BOF steel
mechanical properties slag
Los Angeles LVS EN 1097-2 19
coefficient (LA), %
Resistance to wear. LVS EN 1097-9 14.4
Nordic test (An), %
Sand equivalent test, % LVS EN 933-8 80 *
Flakiness Index (F7), % LVS EN 933-3 2
Flow coefficient (Ecs) LVS EN 933-6 43 *
Water absorption, % LVS EN 1097-6 2.4
Grain density, Mg/m3 LVS EN 1097-6 3.25
Fine content, % LVS EN 933-1 0.5
Freeze/thawing (MS), % LVS EN 1367-2 3
Expansion, % LVS EN 1744-1 p.19.3 2
Methylene blue LVS EN 933-9 -test
(MB), g/kg
Carbonate content, % LVS EN 196-21 -Rigden
air voids, % LVS EN 1097-4 -Delta
ring and ball LVS EN 13179-1 -test,
[degrees]C
Physical and Dolomite Crushed dolomite Crushed
mechanical properties waste sand aggregate quartz sand
Los Angeles -- 22 -coefficient
(LA), %
Resistance to wear. -- 15.7 -Nordic
test (An), %
Sand equivalent test, % 60 -- 91
Flakiness Index (F7), % -- 12 -Flow
coefficient (Ecs) 33 -- 35
Water absorption, % -- 2.7 5.4
Grain density, Mg/m3 2.80 2.80 2.70
Fine content, % 18.6 0.9 0.9
Freeze/thawing (MS), % -- 9 -Expansion,
% -- -- -Methylene
blue 0.5 -- -test
(MB), g/kg
Carbonate content, % > 90 -- -Rigden
air voids, % 28-30 -- -Delta
ring and ball 11 -- -test,
[degrees]C
NOTE: * BOF steel slag 0-5 mm.
Table 3. Conventional and co-product aggregate gradation
Conventional aggregate
Sieve, mm BOF steel slag
0/5 2/5 4/8 8/11
11.2 100 100 100 81.8
8.0 99.9 100 94.6 17.9
5.6 99.2 99.2 47.6 4.7
4.0 95.6 62.4 16.3 2.0
2.0 66.4 22.4 4.4 1.3
1.0 39.3 14.1 3.6 1.2
0.5 21.6 10.1 3.4 1.2
0.250 11.4 7.5 2.8 1.0
0.125 6.0 5.1 2.0 0.8
0.063 3.5 3.6 1.4 0.8
Category [G.sub.A]90 N/A [G.sub.C]90/20 N/A
Passing, % Co-product aggregate
Sieve, mm Dolomite waste Crushed dolomite
sand
0/2 2/5 5/8
11.2 100 100 100
8.0 100 100 88.4
5.6 100 93.0 11.7
4.0 99.5 57.6 3.1
2.0 90.1 9.1 1.8
1.0 67.1 2.7 1.5
0.5 52.9 2.0 1.3
0.250 44.4 1.8 1.2
0.125 34.6 1.7 1.0
0.063 18.6 1.4 0.9
Category [G.sub.F]85 [G.sub.C]90/15 [G.sub.C]85/15
Sieve, mm Crushed
quartz sand
8/11 0/5
11.2 90.7 100
8.0 16.1 100
5.6 4.1 98.4
4.0 1.7 89.6
2.0 1.3 71.9
1.0 1.3 55.0
0.5 1.1 34.9
0.250 1.0 10.5
0.125 0.9 1.4
0.063 0.7 0.7
Category [G.sub.C]90/20 [G.sub.A]90
NOTE: N/A--not applicable.
Table 4. Typical characteristics of the bitumen BND 60/90 and PMB
45/80-55
Parameter Bitumen Standard
BND 60/90 PMB 45/80-55
Penetration at 65.0 59.0 LVS EN 1426
25 [degrees]C,
dmm
Softening point, 50.4 67.7 LVS EN 1427
[degrees]C
Fraas temperature, -25.0 -16.0 LVS EN 12593
[degrees]C
Kinematic 607 -- LVS EN 12595
viscosity,
[mm.sup.2]/s
Dynamic 340 -- LVS EN 12596
viscosity, Pas
Elastic -- 88 LVS EN 13398
recovery, %
Ageing characteristics of bitumen under the influence of heat and air
(RTFOT method)
Loss in mass, % -0.1 0 LVS EN 12607-1
Retained 70.8 40.0 LVS EN 1426
penetration, %
Increase of a 6.4 1.9 LVS EN 1427
softening point,
[degrees]C
Fraas breaking -20.0 -- LVS EN 12593
point after
aging, [degrees]C
Retained elastic -- 84 LVS EN 13398
recovery, %
Table 5. Characteristics of wheel tracking test
Asphalt mixes
Reference Co-products, 100%
(natural dolomite
aggregate)
Bitumen BND 60/90 PMB 45/80-55 BND 60/90 PMB 45/80-55
[WTS.sub.AIR], 0.29 0.28 0.12 0.03
mm/1000 cycles
[RD.sub.AIR], mm 5.78 5.05 1.54 1.47
[PRD.sub.AIR], % 14.45 12.63 3.85 3.68
Asphalt mixes
Combination of
co-products
and natural aggregate
Bitumen BND 60/90 PMB 45/80-55
[WTS.sub.AIR], 0.19 0.22
mm/1000 cycles
[RD.sub.AIR], mm 3.94 3.83
[PRD.sub.AIR], % 9.85 9.58