Sulfur extended heavy oil fly ash and cement waste asphalt mastic for roofing and waterproofing

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

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

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

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

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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

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uniformstress

Fig. 1 Tensile bondstrength test setup


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)


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


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)


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)


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)


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


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


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


LMD 3.2592 1.01 0.440 Insignificant

Ductility (cm)

Sulfur 3.4903 0.33 0.803 Insignificant



CKD 3.2592 15.63 0.000 Significant


LMD 3.2592 4.76 0.016 Significant

Penetration (dmm)

Sulfur 3.4903 3.47 0.051 Insignificant





LMD 3.2592 0.62 0.659 Insignificant

Viscosity (cP)






LMD 3.2592 1.91 0.173 Insignificanta


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

Sulfur extended heavy oil fly ash and cement waste asphalt mastic for roofing and waterproofing

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