Polymer-modified asphalt

Copolymer technology is progressing along two "fronts." First, new appHcations for copolymers are being found to increase the volume of materials that are already commercially available. One example of this is the rapid growth of styrenic block copolymers sold as asphalt (qv) and polymer modifiers over the past 10 years (Fig. 7). Another is the increased interest in graft and block copolymers as compatihilizers for polymer blends and alloys. Of particular interest are compatihilizers for recycled polymer scrap. 

J. L. Goodrich, "Asphalt and Polymer-Modified Asphalt Properties Related to the Performance of Asphalt Concrete Mixes," Msphalt Paving... 

Polymer-modified asphalt is a cold-applied liquid waterproofing system. As with the Sonneborn system mentioned above, the quality of the installation depends on the applicator (it is difficult to achieve an even coating on a vertical surface). High-grade polymer-modified asphalt is superior to coal tar-modified polyurethane in elasticity, crack-spanning ability, and resealability, but inferior in its resistance to chemicals. 

MAJOR APPLICATIONS Asphalt modifiers, adhesives, sealants, coatings, footwear, polymer modifiers, and oil gels. 

Development of semiflexible pavements, executed by grouting the voids of open-graded asphalt concrete with polymer-modified paste [35]... 

Drainage pavements coated with polymer-modified paste containing photocatalyst (ana-tase-type titanium dioxide) (which effectively decompose car exhaust gases with nitrogen oxides on road surfaces by the action of the photocatalyst and prevent air pollution) Special semiflexible pavements with water retentivity, executed by grouting the voids of open-graded asphalt concrete with polymer-modified paste containing superabsorbent polymers to prevent a heat island phenomenon in urban areas... 

Both the chemical nature and the concentration of polymeric modifiers in polymer-modified bitumens can be determined by DSC. The aging behavior of bitumen and polymer-modified bitumen in road asphalt or of bitumen extracted from road asphalt, may be analyzed and characterized by thermoanalytical methods. Thermogravimetry in inert gas has shown, for example, that the concentration of evaporable components decreases as a consequence of aging whereas the coke residue (residue at 600 °C or 800 °C oven temperature) increases, and that is connected with an increase in the concentration of asphaltenes. 

The most technologieally advaneed products are used for waterproofing and pipeline coatings. These products are also based on dispersion of asphalt in the above mentioned solvents but reinforced with addition of polymer. The addition of polymer modifies the plastie behavior of asphalt and renders it elastomeric. Additional solvents are usually added to improve the solubihty of polymerie eomponents. Reaetive polyurethanes are the most frequently used modifiers for waterproofing hquid membranes. Toluene and xylene are the... 

The cohesion of stabilised binder from polymer-modified cut-back and fluxed bituminous binders, which are used for surface dressings, shall be determined in accordance with CEN EN 13588 (2008). For binders used in asphalt mixes, the test methods given in either CEN EN 13587 (2010) or CEN EN 13589 (2008) rosy be used. For binders used in other applications,any one of the three methods listed above, CEN EN 13587 (2010), CEN EN 13589 (2008) or CEN EN 13588 (2008), msy be used. 

Bitumen modifiers can be synthetic polymers, natural rubber (latex) and some chemical additives such as sulfur and certain organo-metallic compounds. Fibres and fillers (inorganic powders) are not considered to be bitumen modifiers. Table 3.16 gives some typical bitumen modifiers, as well as significant improvements to asphalts. Polymers are the most common type of bitumen modifiers, with thermoplastic elastomers being the most popular polymer. 

Permanent deformation behaviour can also be determined by using the triaxial cyclic compression test (see Section 7.6.2). Figure 3.13 shows results obtained when asphalt concrete mixtures were used (AC 20 mm) with and without polymer-modified bitumen. 

However, it does not improve the elastic behaviour of the asphalt (bituminous mixture). Thus, asphalts with thermoplastic polymer-modified bitumen present good resistance to deformation at high ambient temperatures, but generally their fatigue cracking resistance is similar to or even less than that of asphalts with unmodified bitumen. 

In an evaluation study on asphalts with modified bitumens, it was found that asphalt layers with thermoplastic polymer-modified bitumen, when laid over cracked and uncracked surfaces, have more intensive cracking within a very short period, in contrast to the asphalt layers where elastomer-modified bitumen was used (Anderson et al. 1999). 

Because of the abovementioned properties and results, the use of thermoplastic polymer-modified bitumen is recommended in areas with high ambient temperatures where the asphalt layers are subjected to high traffic loads but not over cracked pavement surfaces. 

Regarding the asphalt s characteristic Marshall properties, the use of thermoplastic polymer-modified bitumen increases stability and decreases when compared to the same asphalt with the same binder content. 

The asphalts produced with thermosetting polymer-modified bitumen have excellent adhesive ability, excellent resistance to deformation, excellent fatigue performance and high stiffness modulus. 

Woolley K.G. 1986. Polymer modified bitumen for extra value asphalt. Journal of the Institute of... 

WMA systems have been used with all types of asphalt mixtures, including dense-graded asphalt, stone matrix asphalt (SMA) and PA. They have also been used with polymer-modified binders and in mixes containing RAP (D Angelo et al. 2008). 

The properties of the residual bitumen, particularly when polymer-modified bitumen is used, should be carried out as per residual bitumen extracted from hot mixtures, after full evaporation of water from the bitumen emulsion. The determination of the properties required, particularly of the elastic recovery, is carried out using the same relevant standards as in hot asphalts (CEN EN 13398 2010). Sampling of the bitumen emulsion is recommended to be carried out from the tank of the slurry machine, at a proposed frequency of every 5 tonnes of delivered bitumen emulsion. It is recommended that that the measured elastic recovery should be >50%. 

The fracture energy can be utilised as a parameter to describe the fracture resistance of asphalt concrete, and the fracture energy parameter is particularly useful in the evaluation of mixtures with ductile binders, such as polymer-modified bitumen. It has been shown to discriminate between these materials more broadly than the indirect tensile strength parameter determined by AASHTO T 322 (2011) (Wagoner et al. 2006). 

Valkering C.P., D.J. Lancon, E. De Hilster, and D.A. Stoker. 1990. Rutting resistance of asphalt mixes containing non-conventional and polymer modified binders. Proceedings of the Association of Asphalt Paving Technologists, Vol. 59, p. 590. 

Guidance on determination of soluble binder content of asphalts with polymer-modified binders... 

The last Windows version release of SPDM 3.0 (Shell 1998) contains modules for thickness design, rutting calculations and asphalt overlay design. Additionally, more emphasis was given to material properties incorporating the use of polymer-modified bitumen. The rutting calculations are now based on creep characteristics obtained from dynamic and not static tests, since it appeared not to be applicable to modified bitumen (Lijzenga 1997). 

Linear viscoelastic properties of polymer modified asphalts (PMAs) were studied at various temperatures and... 

Polymer modified asphalt originated in Europe in the early 1960s. Atactic PP is still used today in asphalt compositions mainly in Europe, Mexico and Asia. A PP copolymer containing 2-10% ethylene is more popular in USA. Thermoplastic block copolymers with styrene end blocks or with a diene midblock like S-B-S and styrene-isoprene-styrene (SIS) and their hydrogenated versions are common modifiers for asphalt [40]. 

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