GB993357A - Methods of reclaiming asphalt - Google Patents

Abstract

Weathered asphalt, which may be in the form of a weathered asphaltic pavement containing asphalt and aggregate or oxidized asphalt, is reclaimed by applying an aqueous cationic or balanced emulsion of a specified type of petroleum fraction free from asphaltenes and containing 20-85% of a paraffin fraction, the residuum being unsaturated hydrocarbons and nitrogen bases. Various suitable petroleum fractions within the range specified above are disclosed. Preferably the paraffinic fraction should have a flash-point above 350 DEG F. and the emulsion should contain a surface-active agent. The amount of emulsion added should be sufficient to penetrate the asphalt but insufficient to produce a free oil phase. The emulsifier may be cationic or a mixture of cationic and anionic components, i.e. a "balanced" emulsifier; fatty quaternary ammonium salts (e.g. cetyl - pyridinium chloride), aliphatic fatty amines, fatty substituted aromatic amines, dodecyl phenol polyethoxyethanol and amidoamino-amine salts of lower fatty acids are specified components. A mixed cationic (0.5-1.5% by weight) nonionic (0.5-2.0% by weight) emulsification system is preferred which is spread, e.g. by spraying, in amounts 0.05 to 0.5 gallons per sq. yd. per inch depth of comminuted pavement. Weathered asphalt compositions containing less than 10% paraffinic fractions are treated with a petroleum fraction to bring the paraffinic content above 10%. Penetration values may be used as a guide to the state of the weathered asphalt. Thus an asphalt having a low penetration value in the range 30-300 is treated to give a penetration value substantially higher in the range 30-300. A method of analysing weathered asphalt compositions and the mode of reclaiming thereafter is disclosed together with a number of suitable treatment fractions which are described in association with various standard specifications controlling uses of asphalt. The resistance of asphaltic pavements to weathering may be enhanced by spreading the emulsion in amounts 0.05-0.15 gal. per sq. yd. per in. depth, at a time not later than the first development of hair cracks.