Applications for Asphalt Modification

The annual worldwide consumption of asphalt was over 90 000 000 metric tons in 1995 and the US used approximately one-third of that total [1], The global asphalt consumption in 1996 is represented in Fig. 12-1 [2]. Greater than 85 % of 30000000 metric tons consumed in USA was used to maintain and improve more than 3 000 000 km (2 000 000 miles) of asphalt roads (Fig. 12-2) with an annual road budget of 85 billion [2]. Federal Highway Trust Fund Authorizations reached nearly 21 billion in 1996. There are more than 6 000 000 km (4 000 000 miles) of roads, and asphalt roads account for 94 % (3 270 000 km) of the paved roads in the US. The other 6 % (200 000 km) are paved with Portland cement concrete, which is primarily used for the heavy traffic area of the interstate highway [1], 

Asphalt production is not very uniform throughout the US. The Midwest has the highest production (40 %), followed by the Gulf Coast (25 %), the East Coast (17 %), the West Coast (11 %), and the Rocky Mountains. 

Over 90 % (16 % of total asphalt consumption as in Fig. 12-2) asphalt used in the U S for non-paving purposes is sold to the roofing industry. Two thirds of that is con- 

Almost 90 % of US paving asphalt consumption is for hot mix. The remaining 10 % of the paving asphalt usage (approximately 7 % of the total asphalt consumption) is comprised of asphalt emulsions, primarily used for preventive maintenance and rehabilitation techniques such as chip seal, slurry seal and microsurfacing. Emulsified asphalts are also used for construction in recycling of old paving materials. 

The use of polymer modified asphalts for hot mix and asphalt emulsions has grown significantly in the US during the last 10 years. The National Center for Asphalt Technology (NCAT) has published a list of reasons for the use of asphalt modification [3, 4]. Asphalt has been modified to  

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Other potential applications of PNCs include layered clays in elastomers for asphalt modification [263] and for tire applications (low air permeability) [264], and layered clay nanocomposites with epoxy [265], unsaturated polyesters [266], vinyl esters [267], and polyurethanes [268] for coatings and composites. 

The combination of high cydic content, low branching, and tram unsaturation imparts Vestenamer with an unusual combination of properties compared to other elastomeric materials. The high tram content causes it to be semicrystalline in the solid state. The mixture of cydic and linear polymer chains results in relatively low-melt viscosity that makes Vestenamer useful for certain applications such as asphalt modification. 

Latex, because it is an aqueous dispersion, is the ideal polymer for modification of an asphalt emulsion. Commercial availability of the cationic form makes SBR latex ideal for chip seal, slurry seal and microsurfacing applications, which are predominantly used for preventive maintenance. 

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