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What are the Types of Modifier in Bitumen?

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By Nurul Hidayah

INTRODUCTION
Bitumen is a black or dark brown non-crystalline solid or viscous material, composed principally of high molecular weight hydrocarbons, having adhesive properties, derived from petroleum either by natural or refinery processes and substantially soluble in carbon disulphide. Refer to Ali Akhber Yousefi (2002), bitumen in pure form is not suitable for modern roads and present traffic, therefore forced engineers to modify bitumen to improve its performance during service life.

The modified binder are more stable under heavy loads, braking and accelerating forces and shows increased resistance to permanent deformation in hot weather. It resists fatigue loads and having better adhesion between aggregates and binders.

TYPE OF BITUMEN MODIFIER AND ADDITIVE

There are 3 type of bitumen modifier, namely :
(1) physical modification
(2) chemical modification
(3) other type modification

The table 1 below showed the type of modifier and example of additive that being used to modify the bitumen.

Table 1: The type of physical modifier and additive used in the material (Read and Whiteoak, 2003)

TYPE OF MODIFIER

TYPE OF ADDITIVE

(1) Thermoplastic Elastomers

  • Styrene – butadiene – styrene (SBS)
  • Styrene – butadiene – rubber (SBR)
  • Styrene – isoprene – styrene (SIS)
  • Styrene – ethylene – butadiene – styrene (SEBS)
  • Ethylene – propylene – diene terpolymer (EPDM)
  • Isobutene – isoprene copolymer (IIR)
  • Natural rubber
  • Crumb tyre rubber
  • Polybutadine (PBD)
  • Polyisoprene

(2) Thermoplastic Polymer

  • Ethylene vinyl acetate (EVA)
  • Ethylene methyl acrylate (EMA)
  • Ethylene butyl acrylate (EBA)
  • Atactic polypropylene (APP)
  • Polyethylene (PE)
  • Polypropylene (PP)
  • Polyvinyl Chloride (PVC)
  • Polystyrene (PS)

(3) Thermosetting Polymers

  • Epoxy Resin
  • Polyurethane Resin
  • Acrylic Resin
  • Phenolic resin

Among many different polymers used in bitumen modification such as thermoplastics, thermosets, thermoplastic elastomers, the rubbers seems to be more attractive. Although thermoplastic elastomers such as styrene-butadiene-styrene triblock copolymer (SBS) or its hydrogenated forms and plastomers such as ethylene-vinylacetate copolymer (EVA) are good bitumen modifiers, rubbers are preferred due to their lower prices. In fact, bitumen is supposed to keep its physical and rheological properties constant at different service temperatures and loading conditions and transforms itself to a low viscosity Newtonian fluid at mixing temperature (165ºC). This type of bitumen is called “ideal bitumen”. Constant rheological properties in a wide range of temperatures correspond to rubbery behaviour. It is concluded that the rubbers should be able to modify bitumen properties very well. Therefore, many types of rubbers were introduced in bitumen (PBR, SBR and its latex, ground tire rubber etc.)

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Chemical modification used the additive such as organo- metallic compounds, sulphur and lignin. It used the chemical agent as additive to modify the characteristic of pure bitumen. Due to vary complex structure of bitumen, chemical modification of bitumen have not been commercialized as physical modification. The types of additive used with different types of modifier clearly shown in Table 2.

Table 2: Type of additive adding to chemical modifier (Read and Whiteoak, 2003; Asphalt Academy, 2007)

TYPE OF MODIFIER

TYPE OF ADDITIVE

Chemical Modifiers
  • Organo-metallic compounds
  • Sulphur
  • Lignin
Fiber
  • Cellulose
  • Alumino-magnesium silicate
  • Glass fiber
  • Asbestos
  • Polyester
  • Polypropylene
Adhesion improvers
  • Organic amines
  • Amides

Antioxidants

  • Amines
  • Phenols
  • Organo-zinc/organo-lead compounds

Natural asphalts

  • Trinidad Lake Asphalt (TLA)
  • Gilsonite
  • Rock asphalt

Fillers

  • Carbon black
  • Hydrated lime
  • Lime
  • Fly ash
Extender
  • Sulphur

CONCLUSION
As conclusion, each modifier has their own additives as modifier agent. There are many modifier materials that can be used to mix with bitumen to improve their performance as paving material. Rubbers are preferred as bitumen modifier due to their lower prices and the availability. Nevertheless, the selection of modifier is depending on the user or company.

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REFERENCES
[1] Ali Akhber Yousefi (2002) “Rubber Modified Bitumens.” Iranian Polymer Journal, 11 (5).
[2] Read, J and Whiteoak, D (2003). “Shell Bitumen Handbook.” 5th. Ed. London.
[3] Asphalt Academy (2007) “Technical Guideline: The Use of Modified Binders in Road Construction.” Pretoria. Asphalt Academy.

We at engineeringcivil.com are thankful to Nurul Hidayah for submitting this very useful information on types of modifiers in bitumen.

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Comments
  • sanjay September 12, 2014 at 7:53 am

    we are into petroleum trading bussines in india and having 6 units of tyre pyrolysis oil our units are generating 30 mt of black carbon every day, wanted to know that carbon black can be mixed in hot bitumen kindly help .

  • Ronald Mukombe October 21, 2016 at 4:52 am

    I need information on the chemistry of Polymer modifiers

  • Sujith kumar January 25, 2017 at 12:37 am

    I do project in asphalt withalter material what is the material i have to use

  • Amina M December 23, 2018 at 10:21 am

    Good morning,
    I am looking to find the best bitumen modifier to increase the sofetning point to more than 100 degrees. We used SBS but the softening point is around 80 degrees, and we have access to the fellowing bitumen
    Bitumen 80-100
    Bitumen 90-100
    Bitumen 60-70
    Bitumen 40-50
    if you can help me out with the best polymer to use to get a higher softening point that will be great.
    Thank you.

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