Review On The Potentials of Natural Rubb
Review On The Potentials of Natural Rubb
Review On The Potentials of Natural Rubb
IOP Conf. Series: Earth and Environmental Science 476 (2020) 012067 doi:10.1088/1755-1315/476/1/012067
Email: mrosli@utm.my
Abstract. In recent times both natural and synthetic rubber were blended with bitumen with
the hope of producing a more durable hot mix asphalt. Although the application of natural
rubber (NR) in bitumen modification have started long time ago prior to crumb rubber; only
few literatures that completely characterised its performance are found today. This review aims
to remind researchers and paving agencies on the benefits of NR rubberised asphalt. The study
draw attention to NR production process and its unique properties, how NR was used to solve
four major asphalt pavement failures namely rutting, fatigue, thermal cracking, and moisture
susceptibility. It also presents barriers limiting the application of NR in bitumen modification
with possible solution. Lastly, the concept of applying NR in warm mix asphalt was
introduced.
1. Introduction
Hot mix asphalt (HMA) is a combined mix of aggregate (about 94 - 96%) and asphalt binder (4 – 6%)
by weight of the total mix. Although the percentage of bitumen is comparatively small; it significantly
determines the performance and durability of the pavement more than the aggregate. This is because
climatic factors such as heat, rain and sun radiation have more effect on the asphalt binder than on
aggregate [1,2]. In the past, the use of unmodified bitumen in road construction was enough in
supporting load from traffic flow. However, high traffic load placed on the road network nowadays
has reached a critical stage. This is due to rapid increase in volume of heavy vehicles coupled with
significant increase in allowable axle weight which leads to premature failure of flexible pavement [3].
In addition, HMA roads show susceptibility to temperature through softening at high temperature and
cracking at low temperature. Therefore, it is essential to improve the quality of asphalt binder with a
material that can lessen its temperature susceptibility, enrich cohesion, increase its viscosity and
elasticity [4].
Through research the idea of modifying bitumen with polymer to increase the pavement design life
and reduce frequent maintenance was developed. Polymer improves the rheological property of
bitumen by dissolving and distribution its long chain molecules to create a network of inter-connecting
polymers. This inter-connecting matrix of long chain polymer molecules is what improves the physical
properties of bitumen. It is worthy to mention that the addition of polymer does not chemically alter
the nature of the modified binder; but rather they only improve its physical properties [5,6]. The
advantage of using polymer modified bitumen (PMB) include higher elastic recovery, higher softening
point, greater viscosity, greater cohesive strength and ductility [7]. Thus, PMB has proven to be an
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution
of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Published under licence by IOP Publishing Ltd 1
2nd International Conference on Civil & Environmental Engineering IOP Publishing
IOP Conf. Series: Earth and Environmental Science 476 (2020) 012067 doi:10.1088/1755-1315/476/1/012067
2. Natural rubber
NR occurs in almost 2000 plant species but only a few are industrially important. The first place being
occupied by Hevea brasiliensis, a tree growing up to 30 m high with a 50 cm diameter of the main
trunk. NR is an elastomer that was originally derived from milky latex found in the sap of some plants
[24]. It is not advised to directly add the raw latex to bitumen because of its high-water content and
defencelessness to bacteria attack. Methods commonly used in achieving high concentration of the
solid rubber includes centrifugation, creaming and evaporation [25,26]. The current global production
of NR is about 12.31 M tons amounting to 46% of the world’s total rubber production. With Thailand
as the world’s biggest producer and exporter (37%) while China is the major consumer of the
commodity [27–29].
2
2nd International Conference on Civil & Environmental Engineering IOP Publishing
IOP Conf. Series: Earth and Environmental Science 476 (2020) 012067 doi:10.1088/1755-1315/476/1/012067
Tapping Cut
Hevea brasiliensis
tree
NR Latex
Tapping Cup
To preserve the NR latex in its liquid form; alkaline solution (usually ammonia) is added to prevent
its coagulation [32]. However, when the latex is allowed to remain in the tapping cup for a day or
more, bacteria is produced which kickstart the coagulation process by removing excess water from the
latex. The produced bacteria release positively charged ions which react with the negatively charged
ions at the surface of the NR latex to initiate the coagulation process, this coagulated rubber is often
referred to as “cuplump rubber”. Tuntiworawit et al. (2005) defines cuplump rubber as a freshly
coagulated rubber where the coagulation takes place in the cup at the tree [33]. To speed up the
coagulation process, formic acid is usually added to the NR latex and the whole process is completed
within 2 – 5 hours. NR latex particles was hypothesized to have a micellar structure (Figure 2) with
hydrophobic rubber core surrounded by mix of lipids and protein at the surface [30].
2.2. Constituents of NR
NR latex contains two phases namely the disperse phase and dispersion medium, the disperse phase
consists of large number of small polymeric particles. The solid content of the latex is between 30 to
40% although it may rise to 45−50% after a long period of non-tapping. The rubber produced from
latex contains hydrocarbon and relatively small quantities of protein, carbohydrates, resin-like
materials, mineral salts and fatty acids [10,30]. The empirical formula of NR is (C5H8)n while the
chemical structure composition is shown in Figure 3 [34,35]. It is imperative to note that the presence
of C=C double bond made it feasible to chemically modify the properties of NR for certain
applications [36].
3
2nd International Conference on Civil & Environmental Engineering IOP Publishing
IOP Conf. Series: Earth and Environmental Science 476 (2020) 012067 doi:10.1088/1755-1315/476/1/012067
4
2nd International Conference on Civil & Environmental Engineering IOP Publishing
IOP Conf. Series: Earth and Environmental Science 476 (2020) 012067 doi:10.1088/1755-1315/476/1/012067
temperatures and tend to crack under stress. For NR modified bitumen; the rubber acts like an elastic
band in holding the bitumen together and dissipate the applied stress as it develops. Upon increase in
temperature the bitumen deforms into a viscous liquid and begins to flow. But the presence of NR
helps in resisting the flow by acting like a membrane [20].
3.1. Rutting
Rutting is a common form of distress on flexible pavement caused by increase in traffic volumes,
truck loadings and higher tire pressures. This distress often leads to hydroplaning which endangers the
road user’ life. It also significantly increase the cost of roads maintenance, fuel consumption as well as
reduce the service life of the pavement [7,48,49]. A study by Sai & Gottala [50] found that addition of
NR decreases the penetration value and increases the softening point of 80/100 PEN bitumen and
conclude that the resistance to flow of the bitumen increases with increase in the percentage of NR.
Similarly, NR in the form of ribbed smoked sheet was added to a 60/70 grade bitumen. It was mixed
using high shear mixer at 150 - 170 ℃ for 2 hours, then incubated at 120 ℃ for 1 day. The study
found that the addition of NR results in the asphalt binder to have lower penetration value with high
softening point, penetration index, torsional recovery and tenacity [4]. This indicates that NR-modified
asphalt paved roads shall have more strength and durability than the unmodified binder.
Furthermore, the rutting performance of incorporating NR Latex modified binder on the
engineering properties of SMA and dense graded mixtures was carried out by Shaffie et al., [7]. The
result show that the modified mix have better resistance to rutting than the conventional HMA mix and
conclude that SMA14 mixture exhibits better rutting resistance than the dense graded AC14 by 41%.
Also a recent research by Siswanto [51] on addition of 6% NR latex to a 60/70 Pen bitumen
significantly reduced the permanent deformation of the asphalt mix from 9.73 mm to 6.20 mm (36%).
And the following conclusions were made, NR reduced the rate of deformation by increasing the
dynamic stability of asphalt mixes. Also, the rate of deformation resistance is directly proportional to
the amount of NR added. Lastly, Krishnapriya [6] also found that NR modified bituminous mixes
exhibits excellent rut resistance.
5
2nd International Conference on Civil & Environmental Engineering IOP Publishing
IOP Conf. Series: Earth and Environmental Science 476 (2020) 012067 doi:10.1088/1755-1315/476/1/012067
The improved adhesion bonding of the aggregate particles is attributed to the increase in viscosity of
the NR modified asphalt [56,57].
Figure 4. Fluorescent micrographs of NR-modified asphalt (a) unmodified AC 60/70 asphalt, (b)
3.2% NR [12].
The micrograph above relatively depicts fine NR domains to uniformly disperse medium in the
asphalt matrix, indicating a good homogeneity with the domain size of NR of approximately 10 μm. A
similar study on the dispersion of NR particles in bitumen using atomic force microscopy (AFM)
identified a network of extensive microstructures mixed with bubbles under heat. The AFM images
show that the rubber particles size was less than 50 nm and well dispersed in the modified binder [40].
When compared with crumb rubber-modified bitumen the latex particle is considerably smaller in size,
smaller size particles improve the stability of asphalt binders considering the balance between
Brownian and gravity forces.
6
2nd International Conference on Civil & Environmental Engineering IOP Publishing
IOP Conf. Series: Earth and Environmental Science 476 (2020) 012067 doi:10.1088/1755-1315/476/1/012067
asphalt binder requires high temperature and high shear rate before a homogenous mix of the blend is
achieved [58,59]. This consumes a lot energy and sometimes results in degradation of the polymer.
Furthermore, the blending process requires special plant mixing or modification of the existing
equipment to carry out the task [60,61]. Likewise, the heating effect causes short term ageing of the
asphalt binder and generates a lot of greenhouse gases to the environment. However, it should be
noted that the cost of periodic maintenance of unmodified HMA pavement will counterbalance the
initial high production cost of the NR modified pavement.
Another challenge of modifying bitumen NR is segregation of the polymers in bitumen. Read &
Whiteoak [62] pointed out the difficulty of crumb rubber dispersion in bitumen, the ineffective
dispersion often results in having a heterogenous blend with the rubber purely acting as an elastic
filler. Although NR (in dry form) faced similar homogeneity issue, it shows better reactivity than
crumb rubber [63]. Theoretically, NR modified asphalt pavement should have a longer life span than
crumb rubber modified asphalt. Though the actual effect needs to be determined through studies and
field trials [64]. Generally, pure polymers are thermodynamically incompatible with bitumen, the
incompatibility is as a result of the differences in molecular weight, density, polarity, and solubility of
the polymer in bitumen [65]. This often results in delamination of the PMB during thermal storage and
adversely affect the material during construction [66]. Therefore, it is critical to overcome this
drawback if NR is to be used in asphalt modification [36].
Nowadays, solvents like toluene or nano-alumina are used to aid in dispersing the NR in bitumen.
Toluene is an aromatic solvent that is widely used in the laboratory for extraction of tar sands and
separation of water from bitumen, it also has the ability of dissolving the asphaltene fraction in
bitumen [67,68]. Ismail et al., [69] examined the effect of using toluene to increase the dispersion of
NR in bitumen. The study immersed 5% NR (by weight of bitumen) in toluene at room temperature
for 24 hours, the treated rubber was then blended to 80/100 penetration grade bitumen at 160 ℃ for
one hour at 2000 rpm. Results from rheological tests shows that toluene does not affect the rheological
properties of the blend when compared with the conventional high shear blending process.
Furthermore, the smaller rubber particle size (Figure 5a) confirms that toluene effectively aids in
dispersing the rubber particles more than the conventional high shear mixing process (Figure 5b). The
study conclude that toluene improved the compatibility of NR modified binder and does not have any
negative effect on the performance of bitumen.
Rubber particles
(a) (b)
Figure 5. Fluorescent images of NR modified Bitumen (a) low shear rate with toluene. (b) high shear
rate without toluene [69].
7
2nd International Conference on Civil & Environmental Engineering IOP Publishing
IOP Conf. Series: Earth and Environmental Science 476 (2020) 012067 doi:10.1088/1755-1315/476/1/012067
4. Conclusion
Sustainable roadway construction of today is enhanced through green technology and the best
approach is by considering renewable natural resources in binder modification or replacement. From
inception; NR modified bitumen was found to enhance the fatigue resistance, temperature and
8
2nd International Conference on Civil & Environmental Engineering IOP Publishing
IOP Conf. Series: Earth and Environmental Science 476 (2020) 012067 doi:10.1088/1755-1315/476/1/012067
moisture stability of flexible pavement by thickening the bitumen thus increasing its rutting resistance.
It also reduces the associated low temperature cracking of the binder through stress absorption.
Furthermore, NR provides better cohesion and adhesion of bitumen with aggregate and improve the
elastic recovery of asphalt binder. As a result, the road surface becomes more durable and distress
free. NR possesses high wet gel strength; it has low cost and has excellent physical properties. Despite
the several advantages of NR modified bitumen there are concerns about its higher energy
consumption, generation of unwanted pollution and short-term ageing during HMA manufacturing
process. In view of that clean asphalt production should involve lowering the manufacturing
temperature without compromising the level of mechanical performance through WMA. Some of the
advantages of applying NR in WMA include lower mixing and compaction temperatures, 30 - 50%
reduction in fuel consumption and significant reduction in the amount of CO2, CO, NOx and SO2
released to the environment. The energy savings translates to lower construction cost and a more
environmentally-friendly road construction setting for the workers.
Acknowledgement
The support provided by Universiti Teknologi Malaysia in the form of research grant
(Q.J130000.2651.16J15), and that of NEEDS assessment from Kebbi State University of Science and
Technology Aliero, Nigeria for this study is highly appreciated.
References
[1] Arabani M and Esmaaeli N 2018 Road Mater. Pavement Des. 0 pp 1–23
[2] Al-maamori M H and Hussen M M 2014 Acad. Res. Int. 5 pp 66–78
[3] Shafii M A, Lai Yew Veng C, Mohamad Rais N and Ab Latif A 2017 Int. J. Appl. Eng. Res. 12
pp 3844–9
[4] Vichitcholchai N, Panmai J and Na-Ranong N 2012 Rubber Thai J. 39 pp 32–9
[5] Al-Mansob R A, Ismail A, Yusoff N I M, Azhari C H, Karim M R, Alduri A and Baghini M S
2014 Appl. Mech. Mater. 505 pp 174–9
[6] Krishnapriya 2015 Int. J. Civil, Struct. Environ. Infrastruct. Eng. Res. Dev. 5 pp 121–34
[7] Shaffie E, Ahmad J, Arshad A K, Kamarun D and Awang H 2016 J. Teknol. 78 pp 11–5
[8] Cooley L A, Prowell B D and Hainin M R 2003 Journal of the Association of Asphalt Paving
Technologists 72
[9] Amirkhanian S, Xiao F and Herndon D 2014 The Evaluation and Specification Development of
Alternate Modified Asphalt Binders in South Carolina
[10] Arayapranee W 2012 Rubber Abrasion Resistance Abrasion Resist. Mater. pp 147–66
[11] Tang N, Huang W, Hu J and Xiao F 2018 Road Mater. Pavement Des. 19 pp 1288–300
[12] Saowapark W, Jubsilp C and Rimdusit S 2017 Road Mater. Pavement Des. pp 1–14
[13] Zhai R, Ge L and Li Y 2018 Road Mater. Pavement Des. 0629
[14] Ling T C, Nor H M, Hainin M R and Lim S K 2010 Proc. Inst. Civ. Eng. - Constr. Mater. 163 pp
19–26
[15] Billiter T C, Davison R R, Glover C J and Bullin J A 1997 Physical Properties of Asphalt-
Rubber Binder 15
[16] Akisetty C K, Lee S J and Amirkhanian S N 2010 Int. J. Pavement Eng. 11 pp 153–60
[17] Keymanesh M R, Ziari H, Damyar B and Shahriari N 2017 Pet. Sci. Technol. 35 pp 1–6
[18] Lo Presti D 2013 Constr. Build. Mater. 49 pp 863–81
[19] Wang H, Dang Z, You Z and Cao D 2012 Constr. Build. Mater. 35 pp 281–8
[20] Ruggles C S 2004 Seminar "Rubber in Transport" pp 9–12
[21] Fernandes S R M, Silva H M R D and Oliveira J R M 2018 Constr. Build. Mater. 160 pp 714–24
[22] Jeffry S N A, Jaya R P, Hassan N A, Yaacob H, Mirza J and Drahman S H 2018 Constr. Build.
Mater. 158 pp 1–10
[23] Rahman M T, Hainin M R and Bakar W A W A 2017 Constr. Build. Mater. 150 pp 95–104
[24] Franta I and Ducháček V 1989 Stud. Polym. Sci. 1 pp 31–64
[25] Greve H-H 2000 Ullmann’s Encyclopedia of Industrial Chemistry (Weinheim, Germany: Wiley-
VCH Verlag GmbH & Co. KGaA)
9
2nd International Conference on Civil & Environmental Engineering IOP Publishing
IOP Conf. Series: Earth and Environmental Science 476 (2020) 012067 doi:10.1088/1755-1315/476/1/012067
[26] Tantatherdtam R 2003 Reinforcement of natural rubber latex by nanosize montmorillonite clay
(Pennsylvania State University)
[27] Azahar N B M, Hassan N B A, Jaya R P, Kadir M A B A, Yunus N Z B M and Mahmud M Z H
2016 Int. J. Agric. For. Plant. 2 pp 212–8
[28] Bangkok Post 2018 Thailand battles for rubber price rebound Bangkok Post Thail.
[29] Medina N F, Garcia R, Hajirasouliha I, Pilakoutas K, Guadagnini M and Raffoul S 2018 Constr.
Build. Mater. 188 pp 884–97
[30] Lim H M and Misni M 2016 Latex Appl. Rheol. 26 pp 1–10
[31] Taira 2017 Freepik
[32] Sridee J 2006 Concise encyclopedia of polymer science and engineering
[33] Tuntiworawit N, Lavansiri D and Phromsorn C 2005 Proc. East. Asia Soc. Transp. Stud. 5 pp
679–94
[34] Stephen R, Alex R, Cherian T, Varghese S, Joseph K and Thomas S 2006 J. Appl. Polym. Sci.
101 pp 2355–62
[35] Varkey J T, Thomas S and Rao S S 1995 J. Appl. Polym. Sci. 56 pp 451–60
[36] Kandil U F, M E S, AMM S, AA R, Kafrawy A F El and Farag R K 2017 J. Civ. Environ. Eng.
07 pp 1–7
[37] Yoksan R 2008 Kasetsart J. (Nat. Sci.) 42 pp 325–32
[38] Muhammad B and Ismail M 2012 Constr. Build. Mater. 31 pp 129–34
[39] Stephen R, Raju K V S N, Nair S V., Varghese S, Oommen Z and Thomas S 2003 J. Appl.
Polym. Sci. 88 pp 2639–48
[40] Wen Y, Wang Y, Zhao K and Sumalee A 2017 Int. J. Pavement Eng. 18 pp 547–59
[41] Airey G D 2002 Constr. Build. Mater. 16 pp 473–87
[42] Bauer G, Friedrich C, Gillig C, Vollrath F, Speck T and Holland C 2013 J. R. Soc. Interface 11
20130847–20130847
[43] Varkey Jy T, Rao S S and Thomas S 1996 Polym. Plast. Technol. Eng. 35 pp 1–11
[44] Lim H M and Misni M 2016 Appl. Rheol. 26 pp 1–10
[45] Varkey J T, Augustine S and Thomas S 2000 Polym. Plast. Technol. Eng. 39 pp 415–35
[46] Tinavallie A 2013 Improving The Ductility And Elastic Recovery Of Bitumen-Natural Rubber
Latex Blend Master dissertation/thesis, UTAR
[47] Häuser I 2016 Impact of rubber tree dominated land-use on biodiversity and ecosystem services
in the Greater Mekong Subregion (University of Hohenheim)
[48] Azahar W N A W, Jaya R P, Hainin M R, Bujang M and Ngadi N 2016 Constr. Build. Mater.
126 pp 218–26
[49] Radhakrishnan V, Dudipala R R, Maity A and Sudhakar Reddy K 2019 Road Mater. Pavement
Des. 20 pp 20–35
[50] Sai K and Gottala A 2015 IJSTE-International J. Sci. Technol. Eng. 2 pp 206–12
[51] Siswanto H 2017 Course Procedia Eng. 171 pp 1390–4
[52] Idham M K, Hainin M R, Yaacob H, Warid M N M and Abdullah M E 2013 723 pp 291–7
[53] Kim S and Coree B J 2005 InTrans Project Reports 15
[54] Roberts F L, Kandahal P S, Brown R E, Lee D-Y and Kennedy T W 1996 Hot Mix Asphalt:
Materials, Mixtures, Design, and Construction (United State: NAPA Research and Education
Foundation)
[55] Shaffie E, Ahmad J, Arshad A K, Kamarun D and Kamaruddin F 2015 InCIEC 2014 (Singapore:
Springer Singapore) pp 873–84
[56] Ahmad J, Yusoff N I M, Hainin M R, Rahman M Y A and Hossain M 2014 Constr. Build.
Mater. 50 pp 567–76
[57] Shafii, Abdul Rahman M Y and Ahmad J 2011 Int. J. Civ. Environ. Eng. 11 06 pp 43–9
[58] Wang H, Liu X, Apostolidis P and Scarpas T 2018 J. Clean. Prod. 177 pp 302–14
[59] Wang H, Liu X, Zhang H, Apostolidis P, Scarpas T and Scarpas T 2018 Road Mater. Pavement
Des. pp 1–22
[60] Larsen D O, Alessandrini J L, Bosch A and Cortizo M S 2009 Constr. Build. Mater. 23 2769–74
[61] Zhang F and Hu C 2015 The research for high-elastic modified asphalt J. Appl. Polym. Sci. 132
10
2nd International Conference on Civil & Environmental Engineering IOP Publishing
IOP Conf. Series: Earth and Environmental Science 476 (2020) 012067 doi:10.1088/1755-1315/476/1/012067
[62] Read J and Whiteoak D 2003 The Shell Bitumen Handbook (Westminster, London: ICE
Publishing)
[63] Heitzman M A 1992 State of the practice: Design and construction of asphalt paving materials
with crumb-rubber modifier. Final Report (United States)
[64] Wang H, Lin E and Xu G 2017 Int. J. Pavement Eng. 18 pp 414–23
[65] Read J and Whiteoak D 2015 The Shell Bitumen Handbook, 6th edition (Thomas Telford Ltd)
[66] Al-Mansob R A, Ismail A, Rahmat R A O K, Borhan M N, Alsharef J M A, Albrka S I and
Karim M R 2017 Constr. Build. Mater. 155 pp 680–7
[67] Backx B P, Simão R A, Dourado E R and Leite L F M 2014 Mater. Res. 17 pp 1157–61
[68] Nourozieh H, Kariznovi M and Abedi J 2016 Measurement and Evaluation of Bitumen /
Toluene-Mixture Properties at Temperatures Up to 190 o C and Pressures Up to 10 MPa
(Society of Petroleum Engineers) pp 1705–20
[69] Ismail A, Al-Mansob R A, Yusoff N I B M and Karim M R 2012 Aust. J. Basic Appl. Sci. 6 pp
97–101
[70] Bernama 2017 Malaysia’s new rubberised road technique a world-first Sun Dly.
[71] Golchin B, Hamzah M O and Hasan M R M 2017 Constr. Build. Mater. 141 pp 578–88
[72] Oner J, Sengoz B, Rija S F and Topal A 2017 Road Mater. Pavement Des. 18 pp 1049–66
[73] Abdulrahman S, Hainin M R, Khairul M, Mohd I, Hassan A and Usman A 2019 Int. J. Eng. Adv.
Technol. 9 pp 90–8
[74] Abdullah M E, Zamhari K A, Hainin M R, Oluwasola E A, Hassan N A and Yusoff N I M 2016
Constr. Build. Mater. 112 pp 232–40
[75] Abdullah M E, Zamhari K A, Shamshudin M K, Hainin M R, Khairul M and Mohd I 2013 Trans
Tech Publications, Ltd., Mar. pp. 1692–1699
[76] Kim H 2010 Performance evaluation of SBS modified asphalt mixtures using warm mix
technologies (Doctor of Philosophy dissertation, Clemson University)
[77] Chowdhury A and Button J 2008 A review of warm mix asphalt (Texas Transportation Institute)
7 pp 75
[78] Xie Z, Shen J, Fan W and Wang L 2014 J. Test. Eval. 42 20130255
[79] Abdulrahman S, Hainin M R, Idham Mohd Satar M K, Abdul Hassan N, Mohd Warid M N,
Yaacob H, Mohd A and Che Puan O 2019 IOP Conf. Ser. Mater. Sci. Eng. 527
[80] Kamal M M, Hadithon K A and Bakar R A 2019 MATEC Web Conf. 4005 pp 1–4
11