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Introduction:

      Wardlaw and Shuler (1992) says “Some engineers believe that asphalt is not what is used to be”, bitumen refined from crude oil, the properties of refined bitumen vary from source to source, because of different oil fields and different distillation process, for that reason, the performance result of bitumen in pavements may out of expectation results. Researchers think about developing new types of bitumen with better performance. Polymers added to pure bitumen to modify properties such as elastic response, cohesion strength, adhesive properties, and viscosity.
The following modifiers used to create modified bitumen:-

1-Crumb Rubber.
2- SBS Polymer (Styrene Butadiene Styrene).
3- SBR Polymer (Styrene Butadiene Rubber).
4-Polyolefin.
5- EVA (Ethyl Vinyl Acetate).
6-LDPE (Low-Density Polyethylene).
7-Block Copolymers (SB, SBS, and SEBS).
8-Chemical additives

      The word of the polymer means "too many parts", polymer consist of the long strand made up from very small chemical monomers joined together end to end. The most common types of polymer used for modifying bitumen is a Styrene Butadiene Styrene (SBS) polymer (Willis, Timm, and Kluttz, 2016; Bowers and Diefenderfer, 2017). The performance of modified bitumen depends on the percentage of SBS polymer, the mixture can be defined as a polymer modified asphalt (PMA) if the concentration of SBS polymer reach 3% by mass of the binder content, more SBS concentration up to 6-7%, the mixture can be defined as a highly-modified asphalt (HIMA) (Lee, Wang and Chen, 2018). Modified bitumen has many advantages can’t apparently expected from pure bitumen, modified bitumen can increase the pavement tensile strength (Meynard, 1974), improve adhesion and cohesion (Momcheva, 1975), improve rutting resistance (Carswell and Denning,1983), low temperature cracking resistance (Jew, Shimizu, Svazic, and Woodhams, 1986), increase long-term crack resistance and long-term deformation resistance (Lee, Wang and Chen, 2018).

      The mixture of bitumen and polymer create a new solution usually called modified bitumen, usually modified bitumen has low storage stability the neat or pure bitumen, and the storage stability is the method to investigate polymer separation occur from asphalt. The mixture of modified bitumen should be prepared and cure a few days to dissolve the polymer with bitumen and create a single-phase solution. During storage time separation may occur due to bitumen-polymer density difference, according to (Brule, 1996; Perez-Lepe, Martinez-Boza and Gallegos, 2007) gravity effect on storage stability, because density of polymer lower than the density of pure bitumen, under the gravitational force the polymer tends to rise to the top surface of the solution. According to (Lee, Wang, and Chen,2018) higher polymer concentration leads lower storage stability, which is mean the possibility of separation is more senior than lower polymer concentration, to eliminate separation occur, stirrer or circulation system should use.


Reference:

1- Willis, J., Timm, D. and Kluttz, R. (2016). Performance of a Highly Polymer-Modified Asphalt Binder Test Section at the National Center for Asphalt Technology Pavement Test Track. Transportation Research Record: Journal of the Transportation Research Board, 2575(1), pp.1-9.

2- Bowers, B., Diefenderfer, S. and Diefenderfer, B. (2017). Laboratory Evaluation of a Plant-Produced High Polymer–Content Asphalt Mixture. Transportation Research Record: Journal of the Transportation Research Board, 2631(1), pp.144-152.

3- Chen, J., Wang, T. and Lee, C. (2018). Evaluation of a highly-modified asphalt binder for field performance. Construction and Building Materials, 171, pp.539-545.

4- Meynard J.Y., "Thermoplastic Mixture of Bitumen and an Elastomer," Ger. Offen. DE 2421696, 28 Nov 1974.

5- Jew P., Shimizu J.A., Svazic M., Woodhams R.T. (1986). Polyethylene Modified Bitumen for Paving Applications, J. Appl. Polym. Sci., 31(8), pp. 685-704.

6- Brûlé, B. (1996). Polymer-Modified Asphalt Cements Used in the Road Construction Industry: Basic Principles. Transportation Research Record: Journal of the Transportation Research Board, 1535(1), pp.48-53.

7- Pérez-Lepe, A., Martínez-Boza, F. and Gallegos, C. (2006). High temperature stability of different polymer-modified bitumens: A rheological evaluation. Journal of Applied Polymer Science, 103(2), pp.1166-1174.


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WRITER PROFILE:-

BALEN ZRAR ABDULSAMAD

BSc- Geotechnical Engineering\Koya University

MSc- Infrastructure Engineering\ Szechenyi Istvan University


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