Literature Review on Possible Alternatives to Tar for Antiskid Layers 2403

Figure 31 TEM micrographs of water borne polymer nanocomposite (WB PNC) emulsions.49 Figure 34 The reaction of an isocyanate with a compound containing hydroxyl functionality results in the formation of a polyurethane.. Introduction Coal tar is derived from crude coke oven tar that is a by-product of the combustion of coal in steel manufacturing. The crude coke oven tar is then refined, through distillation, into a number of products, including various grades of road tar (RT). RT-12 grade refined coal tar, which conforms to the requirements of EN 13847 [EN 13847, 2001]. These grades are used to produce coal tar emulsion pavement sealers. Unlike asphalt pavements with bitumen as binder (which can be damaged and eventually destroyed by the effects of thermal and UV induced oxidation, erosion caused by moisture, gasoline and oil drippings, salt and chemicals), coal tar emulsion pavement sealers, due to the refined tar's unique chemical and molecular structure, are inherently resistant to these elements and provide protection superior to asphalt based pavement sealers. Regular application of coal tar emulsion pavement sealers will protect the pavement surface and extend the service life of the pavement. In airports, there are different areas such as runways, taxiways, aprons and parking areas. For runways, good skid resistance and water drainage of the surface layer is necessary [Airfield uses of asphalt, EAPA 2003]. Tar, because of its good adhesion properties and other advantages as mentioned above, is widely used in thin, high skid resistance surfaces. Figure 1 Construction of antiskid layer on the airfield Tar however is toxic and carcinogenic because of its high benzene content. This material did not meet the Dutch environmental standards. In the Netherlands and many other countries, the use of tar in pavement applications is not allowed anymore because of the 6 environmental concerns. The only temporary exception for the use of tar is for the earlier mentioned antiskid layers for airport applications (See Figure 1), will not be allowed anymore after 2010. Therefore, alternatives for tar-bearing antiskid layers are under investigation for a number of years. On one hand, alternatives should of course satisfy the basic requirements of enough friction between tire and surface and enough macro-texture to prevent aquaplaning. On the other hand, alternatives should have the same or even better properties compared to tar-bearing antiskid. Alternatives must at least have the following properties [Argue 2005，and Shoenberger 2007]: 1. very good adhesion properties of …