How is tire rubber removed from the runway?
(wikimedia.org) High pressure water removal.


  Runway rubber removal [requires] high pressure water, abrasives, chemicals and/or other mechanical means.


ICAO Annex 14 notes:


  The surface of a paved runway shall be maintained in a condition so as to provide good friction characteristics and low rolling resistance. Snow, slush, ice, standing water, mud, dust, sand, oil, rubber deposits and other contaminants shall be removed as rapidly and completely as possible to minimize accumulation.


And ICAO Doc 9137 Part 2 Chapter 8 talks about the different methods. Of the methods not mentioned on Wikipedia is hot air blasting. The document notes that high pressure water is only suitable for light deposits. For the chemical they note:


  Chemicals having a base of cresylic acid (a derivative of creosote) and a blend of benzene, with a synthetic detergent for a wetting agent, are used for removal of rubber on concrete runways. For removal of rubber on asphalt runways, alkaline chemicals are applied.


High pressure water and hot air are considered mechanical methods.




(airport-technology.com) Friction tester.

A friction tester is used to determine if a runway needs rubber removal, note the 5th wheel above. A fixed load is applied to that wheel, and any slipping is noted by sensors as the car drives up and down the runway.



Related: Do landing strips suffer from landing wheel tire tracks?