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Impact of mica content on water sensitivity of asphaltconcreteSafwat F. Said a , Karl-Johan Loorents a & Hassan Hakim aa VTI , Swedish National Road and Transport Research Institute , Linkoping, SwedenPublished online: 22 Dec 2008.
To cite this article: Safwat F. Said , Karl-Johan Loorents & Hassan Hakim (2009) Impact of mica content on water sensitivityof asphalt concrete, International Journal of Pavement Engineering, 10:1, 1-8, DOI: 10.1080/10298430701771791
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Impact of mica content on water sensitivity of asphalt concrete
Safwat F. Said*, Karl-Johan Loorents and Hassan Hakim
VTI, Swedish National Road and Transport Research Institute, Linkoping, Sweden
It is well known that mineral fillers have an important influence on the performance of bituminous mixtures. Properties of
filler are depending on the type and the nature of mineral filler. Experience has shown that presence of mica in the filler
material has reduced the asphalt concrete resistance against water influence and freeze and thaw cycles. The purpose of the
present work is to clarify the effect of free mica in the filler material on the durability of bituminous mixtures. Presence of
free mica results in a tremendous increase of the total surface area of aggregate, which is intended to be covered by a
bitumen film. It is concluded that making mix design in respect to surface area of the filler will almost vanish the
disadvantage of using mica in production of asphalt mixtures. It will also result in using less amount of mineral filler.
Keywords: mica; bituminous mixture; durability; filler; stiffness modulus; specific surface area
1. Introduction
The fine aggregate, including the filler material, is an
important part of asphalt mixture. The total specific
surface area (SSA) of the aggregate, which should be
covered by bitumen, is highly dominated by the SSA of
the finer grain fractions (Hyyppa 1964, Anderson et al.
1992, Huang 2006). For an optimum performance, the
aggregate surfaces in a mix are intended to be covered
by a bitumen film. Substituting the fine material (i.e.
filler) in an asphalt mixture with a material with a
noticeably different SSA will influence the thickness of
the bitumen film and thus the asphalt mixture properties,
given that the binder content is constant. A change of the
SSA or aggregate volume must be accounted for in a
mix design.
Fine aggregate with a high content of mica is common
in Swedish crushed rock aggregates. The fine fraction of
aggregates containing mica could have a high level of SSA
due to its mineralogical grain shape and amount
(Santamarina et al. 2002, Loorents et al. 2007). Filler
material with a high content of mica is usually avoided for
use in asphalt mixtures. Presence of mica in the filler
material affects the durability of mixes, in particular
concerning water sensitivity as reported by Hobeda (1988)
and Miskovsky (2004).
The overall objective of this study is to define the
effect of mica in the fine aggregate on the durability of
asphalt concrete. Industrial mica and mica filler from
several quarries located throughout Sweden were used in
asphalt mixtures for preparing asphalt specimens. The
specimens were laboratory tested for water sensitivity and
exposed to freeze–thaw cycles.
2. Experimental programme
To study the effect of mica on the asphalt concrete
properties an experimental programme of three steps was
designed based on laboratory testing of specimens.
Testing was designed to check if mica content had an
effect on the water sensitivity of the mix. In the first trial,
the mix formula was based on weight percent without
respect for type and volume of filler, which is according
to Swedish practice. The mix formula of the second trial
was based on volume proportioning after substituting a
part of fine material with mica (muscovite). Finally, in the
third trial micaceous fine aggregates from various
quarries and frequently used filler in production of
asphalt mixtures were used in consideration of the
conclusions from the first and second trials. The third trial
is to verify the results of the former trials and to come out
with recommendations for use of micaceous fillers in
asphalt mixtures. A commercial mica was used for the
first and second trial, whereas in the third trial filler with a
varying amount and kind of mica (i.e. muscovite and
biotite) was used.
The bituminous mixes used in this work were a
typical road base mix, type AG16/160-220 according to
the Swedish Road Norm (2005). The bitumen content is
4.8% of the pen 160–220 dmm type, with a maximum
aggregate size of 16mm and air void content of 4.5%
according to the recipe. The coarse aggregate is a
medium grained grey to red granite. The mineralogical
composition is quartz (40 vol%) . K-feldspar (36 vol%)
. plagioclase (14 vol%) . muscovite (4 vol%) . biotite
(3 vol%) . chlorite (3 vol%) with accessory opaque
minerals, apatite, epidote, and zircon. The influence of
ISSN 1029-8436 print/ISSN 1477-268X online
q 2009 Taylor & Francis
DOI: 10.1080/10298430701771791
http://www.informaworld.com
*Corresponding author. Email: [email protected]
International Journal of Pavement Engineering
Vol. 10, No. 1, February 2009, 1–8
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presence of mica in the coarse aggregate is not considered
in the present work.
The water susceptibility of the asphalt mixtures were
tested by storing the specimen in concentrated NaCl
solution and by exposing the specimens for freeze–thaw
cycles followed by stiffness modulus measurements.
Change in stiffness modulus after conditioning is taken
as indicator for water susceptibility of a mix. Conditioning
of the specimens in principle is described by Hobeda
(2000). Conditioning of the compacted specimens and
testing has been accomplished using the procedure
presented in Appendix 1.
Stiffness modulus, which is a non-destructive test, by
means of Indirect Tensile Test (the Swedish Standard FAS
Method 454-1995 and EN 12697-26:2004 Annex C) was
used as an indicator for water susceptibility in all three
stages. The stiffness modulus measurements were
performed on dry specimens before exposing the speci-
mens to the conditioning procedure. The specimens were
tested after a set number of conditioning cycles to note any
changes in measured properties. All stiffness measure-
ments were performed on specimens at 10 8C.
2.1 First trial – constant filler weight with industrialmica
The purpose of this trial is to quantify the impact of mica
content in fine material according to Swedish practice,
which means mix composition of asphalt mix based on
weight percent without respect for volume of mix
components.
2.1.1 Specimen properties
Four test series of asphalt mixtures were manufactured
with different mica (i.e. commercial muscovite) content
in the filler aggregate. For three of the series parts of the
baghouse filler content were substituted by 1, 2 and 4% of
the total aggregate by weight of mica, beside a fourth
unaltered reference series. Thus the mica content of the
filler for the test series was 0, 18, 36 and 73% by weight,
respectively. Grain size distribution for the commercial
mica and the final grain size distribution of the asphalt
mixtures are presented in Appendix 2. Table 1 shows that
despite the higher theoretical maximum density of mica,
the air void content of dry compacted mica filler is more
than two times that of the baghouse filler according to the
Rigden method (the Swedish Standard FAS Method
252-2002). In the Rigden test, the mineral filler is
compacted in a container and the dry bulk density is
determined. Figure 1 visualises this difference in bulk
volume of 100 g dry mica and baghouse fillers. The platy
grain shape of mica particles was expected to give rise to
high bulk volume. This indicates that mica filler, which
has higher bulk volume, increases the demand for
bitumen in the mixture in comparison to baghouse filler
with equivalent weight. If the bitumen content in a
mixture is not enough to coat the aggregate particles, then
it appears logical that the mix will have a low resistance
to water influence.
Each series consisted of five specimens compacted
with gyratory compactor. The specimens were manufac-
tured at 150mm in diameter and 65mm in thickness. The
gyration angel was set to two degrees with six bar
pressure. The target was to compact all specimens to the
same void content (4.5%) due to the importance of void
content for water sensitivity. Table 2 shows the average
void contents with the number of gyrations for all asphalt
mixture series. The mica substituted mixes with an
increasing amount of mica needed a larger number of
gyrations to produce specimen of the same void content.
It is, the authors believe, that testing at the same void
content is more important than testing at the same
compaction work, hence the impact of water on asphalt
concrete properties were studied. Manufacturing speci-
mens at the same void content should result in the same
amount of sucked water for all series.
2.1.2 Retained stiffness modulus
The mix formula was based on weight percent,
without considering the volume of aggregate, according
Figure 1. Comparison between bulk volumes of baghouse fillerand commercial mica.
Table 1. Physical properties of baghouse filler and commercialmica mineral used in this work.
Filler type
Theoreticalmaximum density,
(g/cm3)FAS method 228
Rigdennumber volume
(%)
Baghouse filler 2.648 32.2Mica filler 2.845 73.7
S.F. Said et al.2
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to the Swedish Roads Norm (2005). A general trend of
decrease in stiffness modulus, after each conditioning
procedure, is illustrated in Figure 2. It is worth mentioning
that two specimens of the reference series were damaged
and three specimens were damaged for series with 2%
(36% mica of total filler content) and 4% (73% mica of
total filler content) mica content after freeze–thaw cycles.
However, no specimens were damaged from the series
with 1% mica (18% mica of total filler). The results of
damaged specimens are not included in the average of the
stiffness modulus illustrated in Figure 2. The asphalt
mixture series with 1% mica substituted has also shown
the largest retained stiffness modulus after water
conditioning and seven freeze–thaw cycles. Figure 3
shows the retained stiffness moduli for the asphalt mixture
specimens. It is noted that the asphalt mixture weakened as
the substituted mica content is more than 1% by weight.
The decrease in retained stiffness can be larger if fractured
specimens are included in the evaluation, as illustrated in
Figure 3. The range of filler content is between 2 and 6%
by weight of aggregate according to the Swedish Road
Norm (2005). Substituting 1% of baghouse filler with 1%
by weight mica could have resulted in optimum value of
filler content in respect to the total filler volume. Further
information including data on swelling properties is
reported by Hakim and Safwat 2003.
It is concluded from the first trial that using more than
1% mica filler instead of baghouse filler based on weight
percent, will give rise to deterioration in the resistance of
an asphalt mixture to water for road base mix, type
AG16/160-220 designed according to the Swedish Road
Norm. This is based on using commercial mica mineral of
type muscovite. It is also concluded that using mica filler
increases the total filler bulk volume substantially, which
in turn has an effect on the total surface area of the fine
aggregate. An increase in the surface area will cause a
raised need of binder content in the mix design to cover all
aggregate particles. If no adjustment of the design mix is
made a deterioration of mechanical properties of an
asphalt mixture, particularly in presence of water and
freeze–thaw cycles, can be expected. It should be pointed
out that there is a limitation in the Swedish Norm for
Roads (2005) in which there is no caution on effect of
volumetric proportioning when using aggregate of
different origin.
2.2 Second trial – constant filler volume withcommercial mica
The purpose of the second trial is to evaluate the impact of
mica content in the mix composition based on volume
proportioning. Furthermore, to justify the impact of mica
content in the fine fraction by comparison with the
conclusions from the first trial.
2.2.1 Specimen properties
In the second trial of this study, four new asphalt
mixture series were manufactured. The asphalt mixture
Figure 2. Average stiffness modulus of asphalt concrete,AG16/160-220, of the first trial at 108C after conditioning withthe number of tested specimens (n).
Table 2. The average of air void contents and compactionenergy (no. of gyration) for the asphalt concrete specimens of thefirst trial.
Percentage ofmica of totalaggregate
Percentageof mica
of total fillerAir void
content (%)No. ofgyration
Reference(baghousefiller, 0% mica) 0 4.5 591% mica 18 4.6 822% mica 36 4.6 1164% mica 73 4.5 400
Figure 3. Retained stiffness modulus of asphalt concrete,AG16/160-220, of the first trail at 108C after seven freeze andthaw cycles with a total filler content of 5.5% by weight of thetotal aggregate.
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was of type AG16/160-220, similar to the mix type used
in the first trial. In the second trial, the bulk volume of
the filler was kept constant in all test series. The filler
material in the reference mixture was from a baghouse
and as in the first trial, the following three series were
substituted by varying amounts of mica (i.e. commercial
mica as used in first trial). The asphalt mixtures were
substituted with 0 (reference), 1, 2 and 2.3% of the total
aggregate by weight of mica. Thus the volume of the
filler content was kept constant at 7.91%, controlled by
using the Rigden method (FAS Method 252-1998). Thus
the mica content of the filler for the test series was 0, 24,
74 and 100% by weight, respectively. The final grain
size distribution of the asphalt mixtures are presented in
Appendix 2. Each series consisted of five specimens
compacted with gyratory compactor as described
previously. The target was to compact all specimens to
the same void content. Table 3 shows the average void
contents with number of gyrations for all asphalt mixture
series. The void ratios for these series are higher than for
the series from the first trial shown in Table 2, hence, it
was impossible to compact the specimens to as low air
void content as in the first trial due to the high content
of mica.
2.2.2 Retained stiffness modulus
Stiffness modulus of asphalt concrete specimens
measurements at 108C and calculated retained stiffness
moduli are illustrated in Figures 4 and 5. Measurements
of the stiffness modulus of the specimens after each
conditioning cycle indicate that there is a slight decrease
in retained stiffness with increasing mica percentage of
the filler content in the mix. The retained stiffness
decreased by about 10%, when 100% (the test series 2.3%
mica by weight of the total aggregate) by weight of the
filler content is substituted by mica particles compared to
the reference mix (Figure 5), under condition of a
constant volume of the filler content. In comparison to the
first trial the retained stiffness modulus decreased
moderately with an increasing percentage of mica of
the filler content. The retained stiffness modulus at the
first trial decreased almost by 50%, when 73% of the filler
content was composed of commercial mica, under
condition of constant weight of the filler content.
Therefore, it is concluded that the volume of the filler
is most important for the durability of asphalt concrete
based on testing commercial mica (muscovite) and
baghouse filler. However, the 10% decrease in retained
stiffness verifies the indication noted by Huang et al.
(2006) that the asphalt mixture performance is influenced
by the physical–mineralogical (chemical) properties of
the fine aggregate materials too. But it should be noted
that an all mica filler is exceptional and is not practically
used in road construction.
2.3 Third trial – micaceous fine aggregates
In the third trial, micaceous fine aggregates from various
quarries and frequently used filler in production of asphalt
mixtures were used in consideration of the conclusions
from the first and second trials. The purpose of the third
trial of the study is to verify the outcome of the first and
Table 3. The average of air void contents and compactionenergy (no. of gyration) for the asphalt concrete specimens of thesecond trial.
Percentage of micaof total aggregate
Percentageof mica
of total fillerAir void
content (%)No. ofgyration
Reference(baghouse filler,0% mica) 0 6.6 511% mica 24 6.4 1082% mica 74 6.4 2382.3% mica 100 6.7 400
Figure 4. Average stiffness modulus of asphalt concrete,AG16/160-220, at 108C at dry condition, after saturation in waterand after three and seven freeze–thaw cycles.
Figure 5. Retained stiffness modulus of asphalt concrete,AG16/160-220, after seven freeze and thaw cycles with a totalfiller content of 7.91% by volume.
S.F. Said et al.4
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second trials and a demonstration of the results for
practical use.
2.3.1 Specimen properties
The third trial complements the study with using fine
aggregates from Swedish crushed rock aggregates
producers with varying content of mica. Table 4 shows
that the differences in the theoretical maximum densities
(FAS Method 228-1995) and Rigden numbers (FAS
Method 252-1998) between fillers are small, hence
implying modest differences in the volume between the
filler materials included in this work. Thus the mix
design was done based on weight percent of components
according to the Swedish Road Norm (2005) and not by
volume percent of components as suggested in the
second trial.
The content (particle %) of free mica grains in the fine
aggregate was obtained by using a polarising microscope
and point counting technique. The collected (dry sieving)
grain size fractions (24–42mm) was analysed according
to the method RILEM AAR-1, Technique 2 (Sims and
Nixon 2003). Thin sections where prepared as grain
mounts (Nesse 2004) from 2 to 4 g of the collected
fraction for each sample. The result of the count is listed
in Table 4 as particle %. The 24–42mm fraction was
chosen due to that optical analysis is still feasible and this
fraction comprise a reasonable amount of the filler
fraction (0–63mm).
To further quantify the content of free mica grains an
additional analysing step was performed by determining
the SSA for the 24–42mm fraction. SSA’s were
determined by the Brunauer–Emmett–Teller method
(BET) of nitrogen adsorption (ISO method 9277) for
grain size fractions 24–42mm (Table 4).
In this trial (third one) of the investigation five new
asphalt mixtures were manufactured with the filler
materials presented in Table 4. The asphalt mixture
type was AG16/160-220 similar to the mixes used in the
first and second trials of this work. The final particle
gradations of the asphalt mixtures are presented in
Appendix 2. The mix proportioning is according to the
Swedish Road Norms (2005), which means mix design by
weight percent. The bitumen content was 4.8% and air
void content 5% according to the recipe. In the third trial,
the filler content in the mixtures is somewhat higher than
in the first and second trails as presented in Appendix 2.
Each series consisted of five specimens compacted with
gyratory compaction as described in the former trials. The
target was to compact all specimens to the same void
content. Table 5 shows the average void contents with the
number of gyrations for all asphalt mixture series. The
void content for the third series is slightly higher than for
the first trial series as shown in Table 2.
2.3.2 Retained stiffness modulus
Stiffness modulus measurements at 108C and calculated
retained stiffness moduli are illustrated in Figures 6 and
7. From the figures, it is obvious that as with the first
and second trials, the stiffness moduli decrease after
each conditioning. However, in the third trial more than
20 freeze–thaw cycles were needed to reach significant
decrease in the stiffness moduli and a significant
difference between mixes in respect to freeze–thaw
sensitivity. The specimens were exposed for 35 freeze–
thaw cycles. The high resistance to conditioning was
unexpected when compared to the first and second trials.
In the first two trials the specimens were placed in a
bowl filled with water (30 l). The set up was time
consuming to freeze and thaw, and probably even more
important the ice formation around the specimen may
have weakened the asphalt specimen. In the third trial,
the specimen was placed in a plastic bag with a
minimum amount of water, just covering the specimen
in order to eliminate the effect of ice formation around
the specimen and also saving time. Nevertheless, in the
present study the purpose has not been to make a
comparison in-between the trials. Hobeda (2000)
reported that usually seven freeze–thaw cycles weakens
most mixes but he manufactured the specimen with 3%
higher air void content than recipe. The high resistance
Table 4. Retained stiffness modulus of asphalt concrete mixes and properties of fine materials from different quarries.
PropertiesQuarry number
No. 1 No. 2 No. 3 No. 4 No. 5
Fraction 24–42mmSSA (m2/g) 0.9261 0.5959 0.7171 1.2082 0.3935Mica (%) 40.8 31.9 9.8 0.6 24.6
Maximum theoreticaldensity (filler; g/cm3) 2.67 2.77 2.82 2.96 2.64Rigden number 36.8 34.0 40.3 36.0 32.2Retained stiffness modulusof asphalt concrete (%) 22.3 34.0 21.7 28.6 42.2
International Journal of Pavement Engineering 5
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of the mixes in this study (third trial?) probably relates
to the changes in freeze and thaw procedures as well as
not manufacturing specimen at high void content. It is an
interesting conclusion that asphalt mixes can be
manufactured with high resistance to water influence
and freeze–thaw actions.
As already indicated in the introduction, the surface
area of fine grain fraction influences the thickness of the
bitumen film and thus the asphalt mixture properties.
Figure 7 illustrates that a decrease in retained stiffness
moduli, indicates an influence of the SSA on the durability
of asphalt mixes related to water and freeze–thaw impact,
implying a connection between durability and the amount
of free mica in the filler. However, some mixes show a
deviant behaviour (e.g. sample Quarry 4 in Figure 7) from
this general trend.
The specific surface of a particle is the ratio of its
surface area to its mass, where the main controlling
factors are particle size and particle geometry. Research
has shown that roughness of the external surface, shape,
porosity and mineralogy may attribute to an increase in
the surface area (Brantly and Mellot 2000). In this context
it should also be noted that the shape of small particles
tends towards platy and rod-like geometries (Santamarina
et al. 2002). The working hypothesis of the third trial is
that there is a basic correlation between the content of
mica, SSA and durability, and that standard BET
technique can be used as a diagnostic tool to asses the
filler fraction.
Comparing sample values in Table 4 confirms the
general trend between durability and the mineralogical
composition of the filler, i.e. a lower SSA of the filler
implies a more durable resistance to conditioning. The
influence of the mineralogical composition is particularly
noticeable with sample 4 (also sample 3). This sample has
the lowest content of mica but the highest SSA of the
studied samples. The reason for the high SSA is that
sample 4 consists mainly of amphiboles and that a
significant part of the amphiboles are altered into
secondary minerals (e.g. clay and chlorite). This kind of
alteration will increase the SSA for any given rock
material, and also affect the technical competence as noted
with sample 4 relative performance in the conditioning
test. Thus mineral composition is a primary parameter that
effect durability.
In an attempt to verify the correlation between the
content of mica, SSA and durability, a multiple regression
analysis was performed despite the limited data. The
relationship between the SSA and the mica content
(independent factors), and the retained stiffness modulus
(dependent factor) is presented in the formula below with a
correlation coefficient (R 2) of 0.82. But keeping in mind
that the correlation coefficient is based on limited data this
correlation should be verified by further tests. Probably
even better correlation may be found by including more
minerals in the statistics analysis. The regression analysis
resulted in the following relationship for the tested mix of
type AG16/160-220:
Rs ¼ 622 27:7 £ SSA2 0:42 £Mica
Table 5. The average of air void contents and compactionenergy (no. of gyrations) for the asphalt concrete specimens ofthe third trial.
Asphalt mixture typeAir void content
(%) No. of gyration
Quarry no. 1 5.0 67Quarry no. 2 5.2 58Quarry no. 3 4.8 57Quarry no. 4 5.0 53Quarry no. 5 4.8 68
Figure 6. Average stiffness modulus for asphalt concrete,AG16/160-220 at 108C at dry condition, after saturation in waterand after a number of freeze–thaw cycles.
Figure 7. SSA of fine (24–42mm) particles and retainedstiffness modulus of asphalt mixes.
S.F. Said et al.6
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where
Rs is retained stiffness modulus in %
SSA is specific area of fine grain fractions, 24–42mm,
in m2/g
Mica is percent of mica particles in grain fraction 24–
42mm.
From the formula it may be concluded that
decreasing the specific area of fine grains from 0.9 to
0.4m2/g will improve the resistance of asphalt mixtures
against frost–thaw action by more than 15% which is an
easy matter to bring about through minor changes in mix
compositions.
Figure 8 demonstrates that the calculated retained
stiffness modulus is quite consistent with the measured
retained stiffness modulus of tested asphalt concrete
mixtures. It will be interesting to validate the relationship
by new measurements.
3. Conclusions
It is illustrated that using commercial mica filler increases
the total filler bulk volume substantially, which in turn has
an effect on the total surface area of the fine aggregate. An
increase in the surface area of aggregate will cause a raised
need of binder content.
Using mica filler (commercial muscovite) instead of
baghouse filler based on weight percent, as practised in
the Swedish Road Norm, will give rise to a significant
deterioration (decrease in retained stiffness) in the
resistance of an asphalt concrete to water and freeze–
thaw cycles. The retained stiffness modulus decreased
almost by 50% when 73% of the filler content com-
posed of commercial mica under condition of constant
weight of the filler content in the asphalt mix. However,
the retained stiffness decreased slightly about 10%,
when 100% by weight of the filler content is consisted
of mica particles compared to the reference mix under
condition of a constant volume of the filler content in
the asphalt mix.
Therefore, it is concluded that the bulk volume of the
filler is most important for the durability of asphalt
concrete and not the type of filler as commonly believed.
This is based on testing pure mica of type muscovite and
baghouse filler. Furthermore, this work supports the
hypothesis that the asphalt mixture performance is
influenced by the physical–mineralogical (chemical)
properties of the fine aggregate materials, hence the
retained stiffness modulus decreased slightly with
increasing content of mica in the filler despite the constant
volume of the filler in the asphalt mixes.
Testing micaceous filler from different quarries
indicated primarily the importance of surface area of
filler materials and secondarily the percentage of mica
content of filler on the durability of asphalt mixes. As
well as the tendency of the mineralogical composition of
the filler material on asphalt properties was obvious.
However, the data is very limited for making an explicit
conclusion.
Testing more micaceous materials and with various
mix compositions is needed for verification of the
conclusion of this work. The influence of the geometrical
and mineralogical aspects of the filler particles could
highlight the durability of asphalt mixes and should help to
better understand the effect of mica content on the water
sensitivity of asphalt mixes.
References
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Figure 8. Relationship between measured and predictedretained stiffness modulus.
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Appendix 1
Water susceptibility
The water susceptibility of the asphalt mixtures was tested by
swelling properties of mixtures and by exposing the specimens to
freeze–thaw cycles followed by stiffness modulusmeasurements.
Change in stiffness modulus after conditioning has been taken as
an indicator for water susceptibility of a mix. Conditioning of the
specimens in principle is described by Hobeda (E&E; 2000).
Conditioning of the compacted specimens and testing in this
work has been accomplished using the following procedure:
Conditioning
(1) Determine the stiffness modulus of the specimens at
108C according to FAS Method 454-98.
(2) Determine the dry specimen volume by dimension
measurements according to FAS Method 448-98.
(3) Immerse the specimens in concentrated NaCl solution
(30%) and vacuum saturate for 10min to a pressure of
6.7 kPa for 3 h and then 30min at atmospheric pressure.
(4) Determine the conditioned specimen’s weight and
volume by dimension measurements and calculate the
water absorption and swelling of each specimen (FAS
Method 448-98).
(5) Store the specimens in NaCl solution in the oven at 408C
for 48 ^ 1 h.
(6) Repeat the immersion procedure with distilled water
(according to point 3).
(7) Measure water absorption and swelling of the specimens
(according to point 4).
(8) Temperate the specimens at 108C and perform the
stiffness modulus measurements.
(9) Store each specimen in a plastic bag with distilled water.
Expose the specimens to three freeze–thaw cycles at a
temperature of 220 ^ 1 to þ20 ^ 18C for 24 h at each
temperature (12 h is supposed to be enough if a
thermocouple is installed in a dummy specimen to
monitor the specimens’ temperatures).
(10) Check the specimens’ condition visually for physical
damage such as cracks etcetera and if no damage repeat
§7 to 8.
(11) Calculate the stiffness modulus ratio by dividing the
stiffness modulus of conditioned specimens to the
stiffness modulus of unconditioned specimens in
percentage.
(12) §9 to 10 can be repeated when no significant decreases
reported after conditioning, usually up to seven freeze–
thaw cycles. In this study up to 35 freeze/thaw cycles
were applied in the third stage until the most of the
specimens were weakened.
Table A1. Particle gradation of industrial mica fine aggregate.
Sieve size mm 0.063 0.125 0.25 0.5 1 2 4Passing weight % 39.5 75.8 92.4 97.7 99.3 99.9 100
Table A2. Particle gradations of the asphalt mixtures studied in this work.
Passing weight %
Sieve size mm 0.063 0.125 0.25 0.5 1 2 4 5.6 8 11.2 16 22.4
First trail 4.4 7.1 12.4 19.2 27.5 38.6 44.6 57.5 70.1 82.3 99.5 100.0Second trail 4.4 7.1 12.4 19.2 27.5 38.6 44.6 57.5 70.1 82.3 99.5 100.0Third trail 5.8 8.5 13.3 19.8 27.9 38.7 44.6 57.5 70.1 82.3 99.5 100.0
S.F. Said et al.8
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