sulfur extended heavy oil fly ash and cement waste asphalt mastic for roofing and waterproofing
DESCRIPTION
In this paper, the effect of differentwaste material fillers, namely heavy oil fly ash(HOFA), coal fly ash, limestone dust, and cement kilndust, and sulfur on the physical properties andperformance of roofing and waterproofing asphalthas been examined. Conventional asphalt consistencytests in addition to a new bond strength test wereconducted on the modified asphalt mastic.TRANSCRIPT
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ORIGINAL ARTICLE
Sulfur extended heavy oil fly ash and cement waste asphaltmastic for roofing and waterproofing
M. A. Dalhat H. I. Al-Abdul Wahhab
Received: 20 October 2012 / Accepted: 31 August 2013 / Published online: 7 September 2013
RILEM 2013
Abstract Waste materials recycling has been the
logical and widely accepted means of conserving the
diminishing global natural resources. This comes as a
result of increased scarcity of raw industrial materials,
coupled with environmental hazard of most of the
waste products. In this paper, the effect of different
waste material fillers, namely heavy oil fly ash
(HOFA), coal fly ash, limestone dust, and cement kiln
dust, and sulfur on the physical properties and
performance of roofing and waterproofing asphalt
has been examined. Conventional asphalt consistency
tests in addition to a new bond strength test were
conducted on the modified asphalt mastic. The results
were analyzed statistically and assessed in accordance
with ASTM D 332 and ASTM D 449 specifications.
HOFA proved to be a superior filler additive compared
to the other three additives. The sulfur mixes were
found to be short on flash point values, but in spite of
this, results show a promising potential alternative and
cost effective material composite having the least
amount of asphalt content.
Keywords Roofing asphalt Mastic asphalt Heavy oil fly ash Coal fly ash Bond strength
1 Introduction
Eighty-five percent of the global demand for asphalt
(over 100 million metric tons per year and growing) is
generated from road construction [1]. Due to the
limited asphalt supply, the remaining 15 % of asphalt
demand which comes mainly from waterproofing
applications is facing a fierce competition that can
only be lessened through an alternative material
supplement, a move that will provide means of waste
recycling, which in turn will help conserve our scarce
natural material resources and promote green con-
struction. In Saudi Arabia, about 10,000 tons of sulfur
is produced from crude refining on daily basis [2].
More than 12 mega tons of cement kiln dust (CKD)
and limestone dust (LMD) combined is yielded yearly,
while 340,000 m3 of heavy oil fly ash (HOFA) waste is
generated annually.
Traditionally, asphalt-based roofing and water-
proofing products were made from air blown asphalt,
but as roofing chemistry became more sophisticated,
various formulations with different viscosity ranges,
physical and mechanical properties (for horizontal and
vertical applications) were developed for specific uses
from a regular asphalt/bitumen by chemical and
mineralogical contents modification, such as pourable
sealers (pitch pocket mastics), elastomeric sealants
(mastics for high movement joints and terminations),
etc. This is due to the fact that the improvements
achieved on the bituminous materials durability and
extensibility (especially at lower temperatures) by
M. A. Dalhat (&) H. I. Al-Abdul WahhabCivil & Environmental Engineering Department,
KFUPM, Dhahran 31261, Saudi Arabia
e-mail: [email protected]
Materials and Structures (2015) 48:205216
DOI 10.1617/s11527-013-0177-3
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adding polymers, result in modified material with
superior physical properties that surpass any other
alternative material for the same cost.
The roofing asphalt polymer modification is well
explored, understood and lots of works were published
on the subject [38]. Apart from polymer, another
major additive which also dictates the final perfor-
mance of this waterproofing mastic asphalt, is the
mineral filler. Studies have been conducted to inves-
tigate the effect of different mineral fillers on certain
properties of the asphalt binder [911], but nearly all
of these works were directed towards the behavior and
durability of asphalt concrete pavement (AC), and not
on roofing or waterproofing applications, besides the
monopoly in the selection of mineral filler type for
roofing purposes [12], which is LMD. The possibility
of an alternative filler additive which is better or
equivalent to limestone in terms of serviceability
performance of waterproofing asphalt has not been
explored so far.
Sulfur extended asphalt (SEA) has been used in
asphalt concrete (AC) due to its improved rutting
resistance and storage stability [13, 14, 15]. Numerous
researches proved that up to 50 % of the asphalt mastic
constituent in AC can be substituted by sulfur without
much affecting the AC engineering properties in terms
of performance and durability [16]. However, these
results cannot be relied upon when it comes to roofing/
waterproofing applications. SEA was also used for
roofing applications [17], but with sulfur just as a mere
extender without fire safety hazard assessment such as
the specification test for flash and fire point (ASTM D
92) or for asphalt roof cement (ASTM D 2822). The
reactions between sulfur and asphalt have been
investigated [18], it was shown that sulfur reacted in
two different ways. At higher temperatures (240 C),it dehydrogenated asphalt; at lower temperatures
(140 C), it combined with asphalt with the inclusionof sulfur, giving a more ductile material. The duration
of asphalt/sulfur mixing was not reported; only up to
15 % of sulfur was used in the study and ductility test
was not conducted at the ASTM specified room
temperature (25 C).There seem to be an environmental concern when it
comes to the use of SEA, due to its emission of
harmful gases like hydrogen sulfide (H2S) and sulfur
oxides (SO2) at high temperature. The emission of
these gases is governed primarily not by the amount of
sulfur in the asphalt, but mainly by the temperature of
handling and amount of reacted sulfur [19, 18].
General safety precaution is to minimize the operation
temperature, so as to contain the concentrations of the
emitted fumes within standard allowable limit [16].
And to restrict workers time exposure through hourly
shift. The use of degassed sulfur has also been
reported [16]. Prolong storage time (beyond mostly
4 h) in hot state, is strongly discouraged. These
conclusions were drawn from researches conducted
on asphalt concrete containing binder modified by up
to 50 % sulfur. Results also shows sulfur asphalt to
have minimal spills contamination and little impact on
surface runoff water [20]. In a similar study, the air
quality around sulfur asphalt plant and in situ were
monitored in terms of H2S and SO2-concentration
[21]. The H2S and SO2-level were found to averagely
range below the standard limit value (5 ppm).
The famous asphalt physical tests such as ductility
test (ASTM D 113), penetration test (ASTM D 5),
softening point (SP) test (ASTM D 36), and flash and
fire point test (ASTM D 92) formed the basis for
general specifications in roofing asphalt cements,
asphalt for waterproofing and damp proofing applica-
tions and so on [22, 23]. There is lack of adequate
standard test to appropriately assess and characterize
the asphalt mastic on its own at semi-finished product
level for this application [24]. In this study, a new
mastic bond strength test has been devised for
assessing its performance.
The influence of sulfur, HOFA, CKD, LMD and
coal fly ash (CFA) on the physical properties of
asphalt, namely SP, ductility, penetration, flash point
and viscosity have been studied. Further, their effect
on its bond strength was also examined.
2 Materials and methodology
2.1 Materials
The asphalt used in this study is the only local
available grade, and it was obtained from Riyadh
refinery. It has the physical properties as shown in
Table 1.
Cement kiln dust and LMD, which are byproducts
of limestone quarrying and cement manufacturing,
were obtained from a local road construction com-
pany. Sulfur was obtained locally from Saudi Aramco
Oil Company. HOFA was collected from Rabiq
206 Materials and Structures (2015) 48:205216
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thermal power station located in the western coast of
the Kingdom of Saudi Arabia, which is the Red Sea
coast. CFA which is not popular in this part of the
globe due to the absence of its material source (coal),
was obtained from Saudi Ready Mix Concrete
Company.
Heavy oil fly ash (HOFA), a by-product of fuel
combustion process, includes diesel and cracked fuel.
It is typically a black powder type of waste material
containing mainly carbon, generated from thermal
electric power plants. Typical chemical constituent
analysis of HOFA is shown in Table 2. The amount of
each element can vary depending on the source of
HOFA [25].
The reuse of HOFA for a wide variety of
purposes can be seen from the recent and old
literature. It has been studied as an adsorption
medium for CO2, the so called carbon capture. Its
potential as a filler reinforcement in light density
polyethylene (LDPE) polymer composite has also
been reported [26]. Results show an improvement in
rheological properties of the modified LDPE. Fur-
thermore, the patented means of improving the
performance of an asphalt binder and concrete with
the use of HOFA has been disclosed [25]. HOFA-
asphalt mixes proved to be within the asphalt
performance grade limits with potential improve-
ment in durability and strength.
2.2 Sample preparation
2.2.1 Sulfur-filler blends
Fillers were placed in the oven for 24 h at 100105 Cprior to mixing in order to eliminate moisture. 800 g of
neat asphalt was poured into a 1,000 ml mixing can;
the can was then placed in an oil bathe at 140145 C[18]. The asphalt is continuously stirred with the aid of
a high speed shear mixer (2500 rpm) until the
temperature equilibrium between the bathe and the
container has been established. Appropriate amount of
sulfur (10, 20 and 30 %) by weight of the 800 g
asphalt was introduced into the mix, and the stirring
will continue for 10 min. Afterwards, the final mix
was poured into four new mixing cans and stored
temporarily for not more than 30 min inside the oven
at 145 C. The four blends were then mixed in thesame manner as previously mentioned with an appro-
priate filler content (10, 15, 20 and 25 %) for 5 min,
the test samples were cast immediately for each blend
to avoid a prolonged storage additive settlement or
separation. The generalized sulfur-filler mastic for-
mulation is given in Table 3.
2.2.2 SBS-sulfur-filler blends
Finely grounded SBS (styrenebutadienestyrene)
powder having high specific surface area was used.
420 g of liquid asphalt was mixed with 5 or 10 % of
the SBS manually with a spatula spoon to ensure
uniform distribution of the polymer particles. The can
was then sealed with the aid of aluminum foil and
paper tape, and placed inside the oven for approxi-
mately 2 h at 160 C for the SBS particulate to swelland soften. This blend was then placed in an oil bathe
at 190200 C and blended with high shear mixer at2,500 rpm for 20 min. The resulting blend was further
divided into two new containers for final mixing with
the mineral fillers. The mineral addition was also done
at the same temperature and speed for 5 min. The
sealed storing helps eliminate the effect of asphalt
oxidation. If the blend design contains sulfur, the
appropriate amount of sulfur was added and the
mixing was carried out for 2 min maximum. The blend
was then put into an oven for at least 20 min at a
temperature above 170 C for the vulcanization pro-cess to complete before the test samples were casted.
Table 1 Asphalt physical properties
Property Magnitude
Ductility (cm) 150?
Penetration (dmm) 67.2
Softening point (C) 52Flash point (C) 342Viscosity (cP) 575
Table 2 Elemental composition of HOFA
Element Weight (%)
Carbon 92.5
Magnesium 0.79
Silicon 0.09
Sulfur 5.80
Vanadium 0.61
Materials and Structures (2015) 48:205216 207
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2.3 Properties measurement
Conventional asphalt physical tests such as ductility
test (ASTM D 113), penetration test (ASTM D 5), SP
test (ASTM D 36), flash and fire point test (ASTM D
92) were first carried out. And an additional viscosity
test (ASTM D 4402), using Brookfield DV II?
rotational viscometer with RV4 cylindrical spindle
of multiplying constant SMC 20, was conducted on
the samples. Then, selective blends were assessed by a
bond strength test, which was developed in this study
to assess the bond strength of asphalt mastics to
smooth aluminum surfaces.
2.4 Tensile bond strength test
The bond strength test was devised to measure the
asphalt mastic ability to resist tensile force and to
transfer a sizable amount of force between two bonded
surfaces. It is also an indicator of the maximum bond
strength the mastic can surmount when subjected to
tension. The test involves loading a 30 mm by 20 mm
by 6 mm prepared sample of the asphalt mastic in
tension at a rate of 1.3 mm/min at 25 C [27]. The loadmagnitude and its corresponding deformation are
measured in the process. The tensile strength is
reported as the maximum stress recorded, which is
obtained by dividing the highest load carried by the
sample before it fails, by the plate area.
The current active specification test method for
asphalt base expansion joint filler (ASTM D 545-08:
standard test methods for preformed expansion joint
filler for concrete construction) has prescribed the
means to check and measure the suitability of joint
sealant performance and durability through various
tests which include failure due to compression test.
However, it failed to include tensile failure test despite
the fact that joint openings are bound to widen during
winter as they are likely to narrow in summer season,
since the concrete does not only expand but also
contract. Another major common defect exhibited by
asphalt waterproofing membrane on flat roofing sys-
tem is the formation of blisters [28]. Blisters propagate
more easily after the initial bond loss between the
membrane and the roofing deck if the membrane is
lacking in tensile strength. A delaminated membrane
having a low tensile bond strength (TBS) will certainly
swell and bulge at the slightest given opportunity, and
as a result facilitates the whole failure process.Ta
ble
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208 Materials and Structures (2015) 48:205216
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2.4.1 Apparatus
The apparatus consists of two 30 mm by 20 mm by
6 mm plates, a mechanism which holds and stretches
the sample while the load is applied as shown in Fig. 1,
and a hydraulic or screwed-up device.
A sample grip having a wedged-like edge slot
matching the size and shape of the plate is fixed to the
load mechanism main frame upper block with the aid
of a short steel rod that is supplemented with spring
bearing to help eliminate any unnecessary compres-
sive force while the sample is being inserted. The
upper part of the mechanism rests on a bearing or
spring suspension system which eliminates any addi-
tional load on the tested sample due to the self-weight
of the upper frame.
2.4.2 Sample casting
The two plates were spaced 6 mm apart and fixed in
position with the aid of a holder; three sides of the
arrangement were wrapped with a non-sticking paper.
The plates and mastic were heated to a workable state
capable of filling the 6 mm 9 20 mm 9 30 mm
space without voids and also to promote sticking to
the plate wall with full strength. The material was
allowed to cool sufficiently before unwrapping it, for
at least 15 min. When necessary, the sample was put in
the freezer after 30 min for 5 min to enable the smooth
removal of the non-stick paper without sample
disturbance. Then, the sample was put in a 25 Cwater bathe for at least 90 min before testing.
2.5 Statistical analysis of results
A two-way analysis of variance (ANOVA) was
conducted on the physical test results obtained with
the additives used as effects/factors, using Minitab 16
statistical software. This is to ascertain the relative
effectiveness of the fillers within the extenders (sulfur)
and also the extenders level of influence on the asphalt
properties. But before ANOVA was selected for the
analysis, model adequacy check was performed on the
data. Tests such as equality of variance test and
normality check test were carried out to ensure the
relevance and appropriateness of the selected test
method.
3 Results and discussion
3.1 Softening point (SP)
The SP is defined as the temperature at which a
bitumen sample can no longer support the weight of a
3.5-g steel ball. It is a measure of the temperature at
which the material will begin to flow (or soften).
Generally, the SP is negatively affected with more
sulfur additive and increases with increment in HOFA
content as shown in Fig. 2. In pure HOFA-asphalt
20mm
top and bottom plates
asp
halt
mast
icfilm
uniformstress
Fig. 1 Tensile bondstrength test setup
Materials and Structures (2015) 48:205216 209
-
blends, an insignificant change can be observed within
1020 % HOFA content, but a drastic additional rise
by about 7 C in SP was recorded for the mixcontaining 25 % HOFA. The initial 10 % HOFA
resulted to almost 18 % rise. On the other hand,
addition of sulfur to the neat bitumen does not seem to
change the SP within 010 % range, but at higher
doses (2030 %) the SP seems to diminish by
approximately 13 %. Combining both sulfur and
HOFA seems to have an overall destructive resultant,
sulfur will lower the SP while HOFA will tend to push
it up. An equilibrium value that is in-between pure
Sulfur/HOFA blend will always be the resulting SP
depending on the relative proportion of these addi-
tives, but will be closer to the HOFA-asphalt blend
value for equal weight combination.
An increase in SP was also observed with higher
LMD content, as shown in Fig. 2, but unlike HOFA,
LMD has little influence on this parameter. A 7 % rise
was recorded for the initial 10 % composition, and
25 % was able to annul the dwindling effect of 30 %
sulfur on the SP. In contrast to HOFA and LMD, the
effect of CKD on SP can be observed to be uniform for
CKD-only blends, as shown in Fig. 2. An average
increment of 1 C can be seen for every 5 % additionalCKD contents. 15 % was enough to nullify the
lessening effect of sulfur on the SP. However, 10 %
sulfur curve proved to be the softest combination,
which might be due to the relatively lesser amount of
filler grains (sulfur and CKD combined). The CFA has
certain positive effect on the SP compared to LMD and
CKD but far below the HOFA level, as can be seen
from the CFA-0 % sulfur in Fig. 2.
3.2 Penetration
This test measures the penetration of a standard needle
into the asphalt binder sample under 100 g weight in
5 s at 25 C. It is a measure of the material hardness atroom temperature.
The manner in which the asphalt penetration is
affected by sulfur additive depends on the amount of
sulfur used to replace the asphalt component. As
reported from previous work [29], at ranges between 0
and 10 % sulfur the penetration seems to be declining
with more sulfur, while beyond this interval it can be
seen to be rising until it is higher than that of neat
asphalt at 30 % sulfur, as shown in Fig. 3. As opposed
to the other fillers, a continuous decline in penetration
with more HOFA is evident for all HOFA mixes,
which can be related to the relative larger surface area
and absorption capacity. The effectiveness of HOFA
in cutting the penetration value of the asphalt has been
attenuated by sulfur additive in the Sulfur-HOFA
blends; the 20 and 30 % sulfur curves exhibited almost
similar penetration.
Fillers (HOFA, CKD, LMD & CFA)0% 10% 15% 20% 25%
Softe
ning
Poi
nt, o
C
40
45
50
55
60
65
70
CKD - 0% Sulfur CKD - 10% sulfur CKD - 20% sulfur CKD - 30% sulfur LMD - 0% Sulfur LMD - 10% Sulfur LMD - 20% Sulfur LMD - 30% Sulfur HOFA - 0% Sulfur HOFA - 10% Sulfur HOFA - 20% Sulfur HOFA - 30% Sulfur CFA - 0% Sulfur
Fig. 2 Softening point versus fillers (HOFA, CKD, LMD and CFA)
210 Materials and Structures (2015) 48:205216
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An abnormal rise in penetration value with increas-
ing CKD/LMD content can be observed for 20 and
30 % sulfur curves, as shown in Fig. 3. Instead of
declining with more filler content as usual, the
penetration keeps rising up to certain filler content
before it begins to drop. The possible explanation to
this different characteristic could be due to the
relatively higher particle size of CKD and LMD
compared to HOFA. This will result to uneven and
sparsely distributed filler-grains which produce less
strong CKD-asphalt-sulfur monolith having weaker
asphalt-sulfur three dimensional spots at lower CKD/
LMD content. When the penetration needle is
released, it passes through these weak spots and easily
pushes downward any CKD/LMD particle blocking its
path. So, even when the CKD/LMD quantity
increases, the result is a more weaker adhesion of
the asphalt-sulfur fluid to the more numerous CKD/
LMD grains. As these fines are increased further, their
downward displacement by the needle tends to slow
down, thus resulting in relatively lesser penetration
value (25 % CKD). At higher sulfur content (30 %
sulfur), the 3-dimensional matrix is more stably
compact due to the presence of surplus unreacted
sulfur crystals [18]. This results in a continuous
decrease in downward and lateral displacement of the
CKD grains as they are now situated in a highly filled
asphalt matrix. The 0 % sulfur-CFA blends exhibited
penetration value similar to those of LMD and CKD,
but higher than that of the HOFA mastic, as can be
seen from Fig. 3.
3.3 Ductility
Ductility is a measure of the ease with which the
material can be deformed plastically at room temper-
ature. Ductility test measures asphalt mastic ductility
by stretching a standard-sized briquette of asphalt
sample to its breaking point at 25 C.Addition of sulfur to the asphalt resulted in low
ductile composite. A loss of more than 50 % in
ductility can be observed from Fig. 4 at 20 % sulfur
content. More significant reduction is evident with the
addition of HOFA to the neat asphalt; initial 10 %
eliminated more than 85 % of the fresh asphalt ductile
property. Even though both sulfur and HOFA nega-
tively affect the ductility individually, a material with
relatively higher ductility than purely HOFA-blend is
obtained when they are combined.
Ductility also decreased with more LMD, but not as
considerably as in the case of HOFA. A drop of about
35 % can be seen at 10 % LMD content, as shown in
Fig. 4. When combined together with sulfur, the
resultant ductility always seems to be lower than both
results obtained with LMD and sulfur when used
individually alone. CKD-asphalt blend shows lower
Fillers (HOFA, CKD, LMD & CFA)0% 10% 15% 20% 25%
Pene
tratio
n, d
mm
@25
oC
0
20
40
60
80
100
CKD - 0% Sulfur CKD - 10% Sulfur CKD - 20% Sulfur CKD - 30% Sulfur LMD - 0% Sulfur LMD - 10% Sulfur LMD - 20% Sulfur LMD - 30% Sulfur HOFA - 0% Sulfur HOFA - 10% Sulfur HOFA - 20% Sulfur HOFA - 30% Sulfur CFA - 0% Sulfur
Fig. 3 Penetration versus fillers (HOFA, CKD, LMD and CFA)
Materials and Structures (2015) 48:205216 211
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ductile behavior compared to their LMD blend
counterparts. A 67 % loss in ductility was recorded
as compared to 35 % for LMD-asphalt mix. But as in
sulfur-limestone blend, the resulting ductility of
combined sulfur-CKD is lower than that of either
CKD-alone or sulfur-only blend. Pure CFA mastics
possess ductility that is even higher than the HOFA-
Sulfur mastics, but lower than all LMD blends, as can
be seen from Fig. 4.
3.4 Viscosity
The addition of sulfur to neat asphalt caused a gradual
drop in its viscosity. Initially (at 10 %), the effect was
minimal with just a decrease of about 2 % since most
of the sulfur elements have reacted with the naph-
thenic component of the asphalt to form polysulfu-
rized aromatics [18], followed by a significant drop of
more than 40 % at 20 % sulfur (Fig. 5) due to the
presence of extra unreacted sulfur colloid. On the
other hand, HOFA shows a tremendous thickening
ability, which could be attributed to its ability to
absorb the oily constituent of the asphalt, and in turn
resulted to a higher interlayer friction. 10 % HOFA led
to about 200 % rise in viscosity. Mixing sulfur with
the HOFA-blend brought the viscosity close to the
original value, especially within 2030 % sulfur and
1015 % HOFA range combinations.
The LMD does not seem to change the viscosity
significantly but an increase of 300 cP could be
noticed for the first 10 % LMD, as can be seen from
Fig. 5. Afterwards, there seems to be no change up to
20 % LMD content. Adding sulfur caused the viscos-
ity to go down below the normal asphalt viscosity; this
was observed for all sulfur containing LMD-asphalt
blend. The CKD blends more or less behaved in a
similar manner as the LMD mixes. The CKD mastics
containing sulfur possess lower viscosity than the neat
bitumen; the viscosity appreciates for CKD-only
blends but not considerably as in HOFA. The CFA-
only mastics show viscosity equal or just a little above
Filler (HOFA, CKD, LMD & CFA)0% 10% 15% 20% 25%
Duc
tility
, cm
@ 2
5oC
0
20
40
60
80
100
120
140
160
CKD - 0% Sulfur CKD - 10% Sulfur CKD - 20% Sulfur CKD - 30% Sulfur LMD - 0% Sulfur LMD - 10% Sulfur LMD - 20% Sulfur LMD - 30% Sulfur HOFA 0% Sulfur HOFA 10% Sulfur HOFA 20% Sulfur HOFA 30% Sulfur CFA - 0% Sulfur
Fig. 4 Ductility versus fillers (HOFA, CKD, LMD and CFA)
Fillers (HOFA, CKD, LMD & CFA)0% 10% 15% 20% 25%
Visc
osity
, (cP)
@ 13
5 oC,
20
rpm
0
1000
2000
3000
4000
5000 CKD - 0% Sulfur CKD - 10% Sulfur CKD - 20% Sulfur CKD - 30% Sulfur LMD - 0% Sulfur LMD - 10% Sulfur LMD - 20% Sulfur LMD - 30% Sulfur HOFA - 0% Sulfur HOFA - 10% Sulfur HOFA - 20% Sulfur HOFA - 30% Sulfur CFA - 0% Sulfur
Fig. 5 Viscosity versus fillers (HOFA, CKD, LMD and CFA)
212 Materials and Structures (2015) 48:205216
-
the CKD and LMD-only mastics, which are all far
below that of the HOFA-only blends, as shown in
Fig. 5.
3.5 Flash point (FP)
Flash point (FP) is a measure of the minimum
temperature at which the material will ignite. It serves
as an indicator for fire risk assessment (safety when
handling and in service).
The mineral fillers and HOFA have little or no
effect on the flash point. The maximum difference
between neat asphalt value and the highest filler
content (25 %) is not more than 15 C, which is verylittle compared to the original 340 C. On the contrary,the sulfur results in more than 100 C decrease for just10 % composition. This is a result of the release of
flammable gases like hydrogen sulfide by the sulfur
modified asphalt at temperature above 149 C [16].Beyond 10 % sulfur content, the rate of decline ceases
to about 5 C for every 10 % more sulfur, which isvirtually insignificant, as can be seen from Fig. 6.
Similar trend was observed for the LMD-Sulfur
mixes as in the HOFA-Sulfur blend. The horizontal
change in flash point due to filler increase tends to be a
little more pronounced with CKD as compared to the
other two additives (HOFA and LMD), especially for
the CKD-only blends, as can be seen from Fig. 6. This
might be due to the diverse additive composition such
as sulphospurite and spurite resulting from the cement
manufacturing. The CFA-only blends show similar FP
result as the HOFA-only mastics.
3.6 Tensile bond strength (TBS)
The bond strength (TBS) slightly increased with more
sulfur initially, and then starts to decline at higher
content as shown in Fig. 7. At lower percent compo-
sition of up to 20 %, most of the sulfur additives got
attached to naphthenic constituent of the asphalt,
forming extra asphaltene in the process [18], which is
Fillers (HOHA, CKD, LMD &CFA)0% 10% 15% 20% 25%
Flas
h Po
int,
oC
160
180
200
220
240
260
280
300
320
340
360
CKD - 0% Sulfur CKD - 10% Sulfur CKD - 20% Sulfur CKD - 30% Sulfur LMD - 0% Sulfur LMD - 10% - Sulfur LMD - 20% Sulfur LMD - 30% Sulfur HOFA - 0% Sulfur HOFA - 10% Sulfur HOFA - 20% Sulfur HOFA - 30% Sulfur CFA - 0% Sulfur
Fig. 6 Flash point versus fillers (HOFA, CKD, LMD and CFA)
SBS/sulfur0% 3% 5% 8% 10% 20% 30%
Bond
stre
ngth
(kN/
m2)
10
100
1000
Bond strength vs. SulfurBond strength vs. SBSBond stregth vs. 5%Sulfur with varying SBS
Fig. 7 Bond strength versus SBS, sulfur and SBS-sulfur mastic
Materials and Structures (2015) 48:205216 213
-
responsible for asphalt hardening. As the percentage
of sulfur increases, the amount of unreacted sulfur
increases in the asphalt medium, creating more sulfur
colloidal network within the mixture. This leads to the
continuous deterioration of the composite TBS.
Conventional roofing and waterproofing asphalt
polymer, styrene butadiene styrene (SBS), caused a
linear increment in the asphalts bond strength. 5 %
SBS resulted to more than three times the maximum
increment in bond strength the sulfur can yield at
20 %, as can be seen from Fig. 8.
The addition of sulfur to the SBS-modified asphalt
resulted in a material with higher bond strength and
elasticity than the SBS-only blend. The sulfur atom
tends to chemically react with the SBS polymer,
forming a cross-link between the polymer chain,
which leads to the evolution of a tough and sticky non-
flowing asphalt composite. At 5 % SBS and 5 %
sulfur, the TBS value raised up to 50 % compared to
5 % SBS-only blend, due to the vulcanizing action of
the sulfur within the SBS polymer chain, as observed
from Fig. 8. The incremental trend continued for
higher content of SBS at 5 % sulfur. At SBS content
below 5 %, the vulcanizing effect is most likely to
form clusters of discrete patches of cross-linked
polymerized asphalt composite, due to insufficient
SBS polymer that will enable the formation of
continuous sulfur-reinforced polymer network. This
might even result in a material with lower strength
than the SBS-only blend.
The vulcanization temperature was a little above
150 C [15]. Once there is a sufficient amount of sulfur
and SBS additive (the average both on equal propor-
tion by weight of asphalt) and the mixing temperature
is within the vulcanizing range with the material stored
within this temperature limit for the reaction to take
full form, the resulting composite will have superior
performance in terms of strength and elasticity than
the SBS-only mix.
The neat asphalts bond strength (TBS) was slightly
above 25 kN/m2. Adding filler to the asphalt generally
results to an increase in TBS, as observed from Fig. 8.
Both CKD and LMD have produced composites with
at least 100 % increase in bond strength compared to
the original asphalt at 25 % content, while the CFA
shows an insignificant increment (below 20 % that of
the neat asphalts). 25 % HOFA yields a material with
12 times BS of the pure asphalt.
Five percent SBS-modified asphalt exhibited
almost twice the bond strength possessed by the
25 % CKD and LMD containing asphalt. Adding
CKD, LMD or CFA to the 5 % SBS blend nearly
tripled its bond strength, but HOFA resulted to more
than just triple the bond strength, as can be seen from
Fig. 8. The 30 % sulfur mix has little additional TBS,
and even the addition of 25 % CKD, LMD or CFA
resulted in a material with lesser TBS than the neat
asphalt. HOFA has little effectiveness in raising the
TBS value in the sulfur blend, with an increase of not
more than 43 kN/m2.
3.7 Results of the analysis of variance
Both HOFA and sulfur significantly affected the SP of
sulfur-filler asphalt blends except the other two fillers,
LMD and CKD. All participating additives in the
sulfur-filler mixes caused a profound influence on the
ductility of the asphalt material. Apart from HOFA
filler, all other additives have a slight influence on the
penetration of the sulfur-filler mixes. Except for CKD
and LMD, all other additives (sulfur and HOFA)
significantly affected the viscosity of sulfur-filler
mastics. The summary of the result ANOVA is
presented in Table 4.
3.8 ASTM specifications
All blends containing sulfur failed to meet the
minimum flash point set-level for ASTM D 449
(Standard specification for asphalt used in damp
proofing and waterproofing), In addition to this, some
Neat Asphalt 30% Sulfur 5% SBS
Bond
Stre
ngth
, kN/
m2
0
100
200
300
400
500
600plain asphalt 25% - LMD 25% CKD 25% CFA 25% HOFA
Fig. 8 Bond strength versus SBS and sulfur-filler asphaltblends
214 Materials and Structures (2015) 48:205216
-
sulfur mastics also dissatisfied the minimum ductility
benchmarks, otherwise they all might have been
classified under Type I material. HOFA-only mixes
are all Type II, and all the CKD- and LMD-only blends
fall under Type I category. Also, according to ASTM
D 312 (Standard specification for asphalt used in
roofing), majority of the sulfur-asphalt blends did not
pass the minimum flash point requirement. Some of
them did not also scale the minimum SP criteria. The
HOFA-only blends fall under Type I, and only 25 %
HOFA composite scrambled to be under Type II.
However, none of the LMD- and CKD-only blends
passed the minimum SP value, except for 20 and 25 %
LMD mixes which barely managed to scale and fall
under Type I. The CFA-only mastics fall under Type I
asphalt in both ASTM D 449 and ASTM D 312
specifications.
4 Conclusions and recommendation
High content of sulfur significantly reduced the bond
strength of filler-asphalt mix, but when used as a
vulcanizing agent along with polymer, it yielded a
superior tensile material than the SBS-alone compos-
ite. The vulcanizing effect of sulfur in polymer
modified asphalt will help minimize the amount of
the not so cheap polymer required for the manufac-
turing of certain asphalt waterproofing materials. All
the fillers affected the asphalt BS positively, with
Table 4 Summary ofstatistical analysis result
a The ANOVA result for
coal fly ash-only mastics is
not shown for table
consistency sake. But it
gives similar result as that
of CKD and LMD
Analysis of variance result obtained at 5 % significance level
Factors/additives Tabular Fvalue Calculated Fvalue P value Inference
Softening point (C)Sulfur 3.4903 8.67 0.002 Significant
HOFA 3.2592 25.64 0.000 Significant
Sulfur 3.4903 4.44 0.026 Significant
CKD 3.2592 1.87 0.181 Insignificant
Sulfur 3.4903 13.33 0.000 Significant
LMD 3.2592 1.01 0.440 Insignificant
Ductility (cm)
Sulfur 3.4903 0.33 0.803 Insignificant
HOFA 3.2592 11.90 0.000 Significant
Sulfur 3.4903 6.20 0.009 Significant
CKD 3.2592 15.63 0.000 Significant
Sulfur 3.4903 4.26 0.029 Significant
LMD 3.2592 4.76 0.016 Significant
Penetration (dmm)
Sulfur 3.4903 3.47 0.051 Insignificant
HOFA 3.2592 7.76 0.003 Significant
Sulfur 3.4903 9.41 0.002 Significant
CKD 3.2592 0.12 0.972 Insignificant
Sulfur 3.4903 10.56 0.001 Significant
LMD 3.2592 0.62 0.659 Insignificant
Viscosity (cP)
Sulfur 3.4903 13.79 0.000 Significant
HOFA 3.2592 72.85 0.000 Significant
Sulfur 3.4903 43.61 0.000 Significant
CKD 3.2592 3.12 0.056 Insignificant
Sulfur 3.4903 55.57 0.000 Significant
LMD 3.2592 1.91 0.173 Insignificanta
Materials and Structures (2015) 48:205216 215
-
HOFA having the greatest impact. Statistical analysis
of the asphalt physical test result shows HOFA to be
more effective than the other three fillers (LMD, CKD
and CFA) in increasing the SP and viscosity or in
reducing the asphalt ductility and penetration. The
significant drop in the flash point of sulfur-asphalt
affected its suitability for use in roofing applications.
Asphalt mastic bond strength test should be
standardized and included in the standard test methods
for preformed expansion joint filler for concrete
construction (ASTM D 545-08) and all other relevant
specifications.
Acknowledgments The authors acknowledge the supportsprovided by King Fahd University of Petroleum and Minerals
and Saudi Arabian Oil Company (Saudi Aramco), Dhahran,
Saudi Arabia in carrying out this research.
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Sulfur extended heavy oil fly ash and cement waste asphalt mastic for roofing and waterproofingAbstractIntroductionMaterials and methodologyMaterialsSample preparationSulfur-filler blendsSBS-sulfur-filler blends
Properties measurementTensile bond strength testApparatusSample casting
Statistical analysis of results
Results and discussionSoftening point (SP)PenetrationDuctilityViscosityFlash point (FP)Tensile bond strength (TBS)Results of the analysis of varianceASTM specifications
Conclusions and recommendationAcknowledgmentsReferences