J Mater Cycles Waste Manag

DOI 10.1007/s10163-014-0289-z

ORIGINAL ARTICLE

Modification of bitumen-based roof covering material by glass

reinforced polyester recyclate
Gökdeniz Neşer • Vural Aytekin

Received: 30 July 2013 / Accepted: 23 June 2014

 Springer Japan 2014

Abstract In boat building industry, environmental leg- Keywords Glass-reinforced polyester waste 
islations promoting recycling of thermoset composites Bitumen-based roof covering material  Boat building 
have been the main driver globally. Recycling of glass- Aging
reinforced plastics (GRP), which is widely used in the
industry, has been very problematic due to its inherent
heterogeneous structure. Considering the urgent need of Introduction
the industry, several investigations have been carried out
to find the beneficial uses of GRP recyclate after Polymer-based thermoset composites have been used since
mechanical recycling which is the most cost-effective the 1950s in boat building industry and they dominate the
technique. In this study that can be considered an effort to related global market at present. Glass-reinforced polyester
find proper way to recycle GRP containing polyester as (GRP) composite, in particular, remains a major focus,
the matrix, the recyclate of waste GRP boat material was with many crafts still being laid up in open moulds by
adopted as modifier for bitumen-based roof covering traditional manual wet lay-up technique. Requiring only
materials. Fine grounded GRP recyclates were added to modest start-up investment, this accessible, entry-level
the hot bitumen mix with the dosages of 1, 3, 5, 10, 20 technology is used for thousands of working and leisure
and 30 % as a part of roof covering material production crafts annually. GRP craft range from 3 m dinghy or tender
process. Performances of the modified end product have boat to ‘plastic’ mine hunters in service with leading navies
been tested conventionally. The tests were also repeated [1]. Boat building industry consumes 6 % of thermoset
for environmentally aged blends that contain 30 % of plastic composites worldwide [2].
GRP recyclate. Results indicate that use of GRP recyclate Although GRP provides design engineers and producers
in the modification of bitumen-based materials is an with moderate quality and long life span, recycling which
effective way to improve roof covering materials’ per- contributes to the sustainability and sustainable develop-
formance in terms of temperature susceptibility in par- ment of industrial processes by leading resource and
ticular and has the potential to solve the recycling energy saving for the production of reinforcement and
problems of the industry. matrix materials has been always a problematic area for
this material. Poor recyclability of GRP as a thermoset
composite is mainly due to the inherent heterogeneous
structure.
Because of technological and economic difficulties,
G. Neşer (&)
Boat Building Research Center, Dokuz Eylül University, GRP recycling is almost limited to the incineration for
Baku Blv. 100 Inciralti, 35340 Izmir, Turkey energy recovery with no or little fibre recovery. After
e-mail: gokdeniz.neser@deu.edu.tr extensive researches on this subject, GRP recycling tech-
nologies yet to be commercialized have been developed in
V. Aytekin
The Graduate School of Natural and Applied Science, Dokuz three categories: mechanical, chemical and thermal [3].
Eylul University, Tinaztepe Campus, Buca, 35160 Izmir, Turkey Among them mechanical recycling involving shredding

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and grinding followed by screening to separate fibre-rich Table 1 Particle size distribu- Particle size wt%
and resin-rich fraction for re-use is the easier way of tion of the grounded E-glassfi-
ber reinforced polyester [0.5 mm 2.25
recycling a thermoset plastic in terms of technological level
recyclate
and initial cost. Being very energy intensive and the re- 0.5–0.355 mm 78.9
cyclates having low quality are the main drawbacks of this \0.355 mm 18.85
technology.
The current and future waste management and Experimental
environmental legislations require all engineering
materials to be properly recovered and recycled, from Materials
end-of-life (EOL) products such as end-of-life vehicles
(ELVs) [4]. Relatively recent environmental legisla- GRP recyclate
tions such as the EU directives for end-of-life vehicles
[4] and for waste electric and electronic equipments [5] To modify roof covering bitumen-based material, fine
as well as latest governmental UK strategy for com- grounded E-glass fiber reinforced polyester recyclate pro-
posites [6] identifying ‘‘Increasing sustainability and vided during the cutting of a boat dismantling process has
recycling’’ cause increasing demand for recycling GRP. been used. The fibres in the form of layers known as stitched
Although both national and global environmental leg- multilayer reinforcements were supplied by Cotech indus-
islations help to promote recycling of thermoset com- tries. Matrix material was an orthophthalic polyester pro-
posites, handling today’s end-of-life products is a duced by Dewilux Inc, in the brand of Dewester 196 as a
considerably important problem whose solutions should general purpose resin which is widely used in small craft
be put into practice. building industry. GRP parts of boat used in this study were
To survive in the boat building industry mainly driven built by hand lay-up method in the workshop of a boat
by environmental legislations, thermoset composites pro- builder in Izmir. Glass fiber content of the product was
ducers and suppliers have to ensure a proper waste man- almost 35 % in weight and bulk density was 670 kg/m3
agement system in time. Considering the urgent need of the while fiber length was shorter than 0.25 mm. Hand lay-up
industry, several investigations have been carried out to was the preferred method since both are used widely in the
find beneficial uses of GRP recyclates obtained from boat building industry due to lower cost and the ease of
mechanical recycling such as using it in manufacturing obtaining uniform thickness throughout the lamination.
artificial woods [7–9], in bitumen-based road asphalt, and Production with this method has been found sufficient where
in cementitious materials to improve their thermal and medium-strength characteristics are satisfactory. Before the
insulation properties [10]. tests, GRP parts are sieved with mesh sizes of 0.71, 0.5 and
As for bitumen, it is a widely used material in con- 0.212 mm according to the ASTM D451-91 [16]. Particle
struction industry due to its good cohesiveness, water size distribution of the material is shown in Table 1.
resistance, and corrosion resistance [11, 12] and avail-
ability. To improve bitumen and bitumen-based materials’ Bitumen
mechanical properties and operational qualities, modifying
them with polymers has been found to be an effective way Bitumens used in this study have been provided from
by the researchers. By this method, decreased high-tem- Aliaga/Izmir Oil Terminal of the Turkish Petroleum
perature susceptibility, improved deformation resistance, Refinery Corporation. Roof covering materials have been
and increased resistance to low-temperature cracking can produced using the pure petroleum-based bitumens that can
be obtained [13–15]. be classified using their penetration values ranging between
In this study, fine grounded recyclate of waste GRP 10 and 300. The much more preferred bitumens in the roof
boat material was adopted as a modifier for bitumen- covering production are identified by B50/70, B70/100, and
based roof covering materials and was added into the hot B160/220 according to the related standard code TS 1081
bitumen mix. Performances of the modified materials EN 12591 [17]. The characteristics of bitumens used in this
have been measured by conventional methods and these study have been given in the Table 2.
tests have also been performed for environmental aged
blends which contain GRP recyclate. Results indicate that Test methods
using GRP recyclate in the modification of bitumen-based
materials is an effective way to improve bitumen-based Conventional bitumen tests
roof covering material’s lifelong performance and has a
potential to solve the recycling problems of boat building Before adding the GRP recyclates, bitumens have been
industry. heated up to 180–200 C. During the preparation of the

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Table 2 Characteristics of bitumens used in this study Specimens have been prepared in sample containers and
Bitumen no. 1 2 3
placed in a water bath at 25 C for 1.5 h before the test.
Grade B50/ B70/ B160/ The precisely dimensioned needle, loaded to 100 ± 0.05 g,
70 100 220 has been brought to the surface of the specimen at right
angles, allowed to penetrate the bitumen for 5 ± 0.1 s,
Penetration (at 25 C) 0.1 mm, dmm 50/70 70/100 160/220
while the temperature of the specimen has been maintained
Softening point (C) 46–54 43–51 35–43
at 25 ± 0.1 C. The penetration is measured in tenths of a
Loss of weight by heating (max. %) 0.5 0.8 1.0
millimetre (deci-millimetre, d-mm). Five determinations
Retained penetration (min %) 50 46 37
have been made on a specimen.
Softening point after TFOT (min C) 48 48 37
Brookfield rotational viscometer has been utilized for
Flash point (min C) 230 230 220
measuring viscosity, or resistance to flow according to the
Solubility (min wt%) 99 99 99
related standard. The appropriate spindle has been attached
Raise of softening point (max C) 9 9 11
to the viscometer, immersed into the sample and allowed it
to rotate with 20 rpm. The viscosity has been calculated
using the appropriate spindle factor. Five calculations have
Table 3 Conventional tests performed for properties of bitumens and
been made on a specimen and averaged.
related standards
Softening point test is to determine the softening point
Test Standard of virgin and modified bitumens within the range
Penetration (at 25 C) 0.1 mm, TS EN 1426 [18] /TS 11758 [19] 30–157 C by means of the Ring-and-Ball apparatus. A
dmm high softening point ensures that they will not flow in
Viscosity (at 135 C), Pa s ASTM D2196-10 [20] service. For a bitumen of a given penetration, the higher the
Softening point ( C) TS EN 1427 [21] /TS 11758 [19] softening point the lower the temperature sensitivity.
Fraass breaking point ( C) TS EN 1109 [22] /TS EN 13164 During the test, specimens have been prepared exactly as
[23] specified in the related standard in precisely dimensioned
Aging TS 7202 EN 60811 [24] brass rings and maintained at a temperature of not less than
TS Turkish standard 10 C below the expected softening point for 30 min
before the test. The rings and assembly, and two ball
bearings, have been placed in a water bath filled to a depth
specimens, the mixtures have been mixed in 600 rpm for of 105 ± 3 mm and the whole maintained at a temperature
120 min. For each bitumen product, six mixtures in dif- of 5 ± 1 C for 15 min. Then a 9.5 mm steel ball bearing
ferent GRP recyclate/bitumen weight ratio (1, 3, 5, 10, 20 (weighing 3.50 ± 0.05 g) has been centered on each
and 30 %) have been prepared and three calculations/ specimen and heat has been then applied to the beaker so as
determinations on samples have been made and averaged to raise the temperature by 5 ± 0.5 C per minute. The
for each type of tests to eliminate possible preparation and temperature at which each bitumen specimen touches the
testing errors. base plate has been recorded as its softening point.
In this study, since the tests have been aimed to inves- Based on penetration and softening point, the penetra-
tigate the possible effects of GRP modifications on the tion index (PI) determined as a measure of the temperature
rheological properties of bitumens, thermal characteristics susceptibility of bitumen has been calculated for all blends.
and workability in particular, penetration, viscosity, soft- The consistency of changes in bitumen depends on the sign
ening point, Fraass breaking point and aging tests accord- and magnitude of PI. For paving-grade asphalt, PI between
ing to related standards have been performed (Table 3). 2 and -2 is suitable for the temperature susceptibility of
Penetration test is to examine the consistency of a bitumen (value of approximately 1 is ideal). A classical
sample of bitumen by determining the distance in tenths of approach related to PI calculation has been given in the
a millimetre that a standard needle vertically penetrates the Shell Bitumen Handbook [25] as shown in Eq. 1:
bitumen specimen under known conditions of loading, time 1952  500  logðPen25 Þ  20  SP
and temperature. The consistency is a function of the PI ¼ ð1Þ
50: logðPen25 Þ  SP  120
chemical constituents of a bitumen: the relative proportions
of asphaltenes (high molecular weight, responsible for where Pen25 is the penetration at 25 C and SP is the
strength and stiffness), resins (responsible for adhesion and softening point temperature of the blends.
ductility) and oils (low molecular weight, responsible for The scope of Fraass breaking point test is to determine
viscosity and fluidity). the temperature at which a bitumen tends to break rather
Penetration test in this study has been performed using a than to flow when stressed. It can be applied for any
penetration apparatus specified in the related standard. homogeneous road or industrial bitumen. A thin flat steel

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plaque, coated with the sample, is flexed under specified Aging

conditions at a descending series of temperatures.
In addition to the below-mentioned tests, the specimens
Fluorescence microscopy modified by GRP recyclate with 30 % weight ratio have
been tested again after accelerated aging. Aging conditions
A fluorescence microscopy has been used to investigate the were both under UV and humidity simulating working
morphology of the SBS and EVA PMBs by determining condition of a roof covering. The aging duration was 672 h
the state of dispersion of the polymer within the base (4 weeks) while the environmental temperature was 80 C.
bitumen. Fluorescent microscopy is based on the principle
that polymers swell due to the absorption of some of the
constituents of the base bitumen and due to the fluores- Results
cence effect in ultraviolet light [26]. The bitumen-rich
phase appears dark or black, whereas the polymer-rich The conventional tests’ results of the bitumens modified by
phase appears light. GRP recyclate with the ratios of 1, 3 and 5 % on weight basis
Samples of each PMB were prepared using a standard are quite same with the virgin bitumens. In order to appreciate
sample preparation method that involves a heating and the effects of modification, the ratios have been increased to
homogenizing procedure and a sample cooling regime as 10, 20 and 30 % and the tests have been performed using
well as a surface preparation procedure over thin films of these new blends. The results obtained from second-stage
the samples [27]. conventional tests have been summarized in Fig. 1.
PMB samples were examined at room temperature As can be seen, modification by GRP recyclate causes a
under a Leica DM EP microscope with ultraviolet light reduction in Fraass breaking point and softening point and
(generated from a high-pressure Xenon lamp) at magnifi- an increase in penetration and viscosity. Penetration and
cation levels of 1009. Images were then taken by a 7.2 Mp viscosity values have been increased with a significant
Leica DFC 320 color camera. amount of 42–82 % that shows an improvement of the pure

Fig. 1 Conventional tests results of the blends with different ratios of GRP recyclate on weight basis

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Fig. 2 Penetration indexes for

the blends with different ratios
of GRP recyclate on weight
basis

bitumens for the aimed applications. Fraass breaking point points. These indicate the degradation of polymer struc-
generally decreases with increasing polymer content. The tures in the blends. However, the results after 4 weeks’
relative improvement seems to be somewhat greater using aging are acceptable for roof covering purposes. Aged
softer bitumens and is likely not influenced by GRP recyc- blends’ results obtained from each tests were very close to
late’s structure. In all cases, reductions in Fraass breaking those before aging. From these results, one can appreciate
point are comparably small (a few C). Regarding the effect that modifying with GRP recyclate provides a better
of GRP recyclate on penetration of binders, penetration workability.
decreases with polymer content; however, in case of Bitu-
men-3 above a certain content (20 % GRP), penetration Morphology
begins to increase with increasing polymer content. For all
blends, penetration (at 25 C) was found to be linearly The morphology of modified bitumen samples has been
correlated with Fraass breaking point. Softening point and investigated using a fluorescent microscope at room tem-
viscosity values increase with increasing GRP recyclate perature by characterizing the nature of the continuous
content for all type of blends. Softening point temperature phase, fineness of the dispersion of the discontinuous phase
has been increased and improved in a range of 12–20 C as well as the description of the phases and shapes.
according to the related bitumen. As for the improvement in A distinction can be made between the samples whose
Fraass, breaking points remained between 2 and 4 C. continuous phase is a bitumen matrix with dispersed
Penetration indexes of the samples have been shown in polymer particles and samples whose continuous phase is a
Fig. 2. Since for all blends the PI values are between -2 polymer matrix with dispersed bitumen globules. The
and 2, they all are suitable for temperature susceptibility. images showing modified bitumen morphology including
Bitumens modified by 20 % GRP show an ideal suscepti- base bitumen through the aging are presented in Fig. 3. In
bility (PI index & 1). the images, the swollen polymer phase appears light while
the bitumen phase appears dark.
Results after aging From the images after aging, GRP waste has been dis-
tributed uniformly in the bitumen and it became a domi-
Conventional bitumen tests were performed after each nant phase after some stages.
week throughout the aging duration for all bitumens
modified by 30 % GRP content. The result obtained is
summarized in Table 4 with an aging index, AI (Eq. 2): Conclusions
Value of the modified bitumen after aging
AI ¼ ð2Þ The objectives of this study were to first evaluate the uti-
Value of the virgin bitumen before aging
lization of GRP recyclate addition on the performance of
For all bitumens, aging causes increase in penetration bitumen-based roof covering materials and second to
and viscosity and decrease in softening and Fraass breaking determine the aging on the reduction of material

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Table 4 Effects of aging on the bitumens modified by 30 % GRP recyclate on weight basis
Bitumen Test Virgin bitumen After 1 week After 2 weeks After 3 weeks After 4 weeks Aging
before aging aging aging aging aging index (AI)

1 Penetration (at 25 C), dmm 34 32 35 38 41 1.24

Viscosity (at 135 C), Pa s 8500 9000 9250 9250 9500 1.12
Softening point, C 66 66 65 63 60 0.91
Fraass breaking point, C -6 -6 -6 -5 -5 0.83
2 Penetration (at 25 C), dmm 22 24 26 28 30 1.36
Viscosity (at 135 C), Pa s 6000 6000 6000 6250 6250 1.04
Softening point, C 66 66 64 63 61 0.92
Fraass breaking point C -6 -6 -6 -5 -5 0.83
3 Penetration (at 25 C) dmm 90 92 96 95 98 1.09
Viscosity (at 135 C) Pa s 3500 3750 3750 4000 4000 1.14
Softening point (C) 55 54 52 52 50 0.91
Fraass breaking point (C) -7 -7 -6 -6 -5 0.71

Fig. 3 Fluorescent images of bitumens’ samples with 9100 magnification

performance. Based on the data presented in this paper, the bitumens by decreasing its penetration and Fraass
following conclusions can be drawn: breaking point and increasing its viscosity and soften-
ing point. These properties of end product obtained by
1. GRP boat recyclate can be incorporated into the
performing conventional tests have demonstrated the
bitumen-based roof covering materials and the addition
increased stiffness (hardness).
of this recyclate can produce improved properties
4. Penetration indexes of modified materials stand in
comparable to conventional (unmodified) roof cover-
acceptable range (between 2 and -2) in terms of
ing materials.
temperature susceptibility. This may conclude that
2. The effect of recyclate addition on the properties of
GRP recyclate modified roof covering materials
roof covering materials containing 1–30 % recyclate
display reduced temperature susceptibility than
was evaluated that all the values increase up to 30 %
base materials.
GRP recyclate.
5. In the light of findings from aging investigatons, it is
3. GRP boat recyclate addition improves the performance
possible to consider that recyclate addition minimizes
of roof covering materials which are made of different

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