Bitumen emulsions are now being used in almost every application in which hot, cut-back or fluxed bitumen binders are used. A survey of current practice in New Zealand for road maintenance and construction from 1987 to 1991 is recorded. Experience ranges from using bitumen emulsion for maintenance, tack coat, sealing, and slurry applications for State Highways, City streets and Council roads, and in Transit New Zealand regions. Binder performance of bitumen in general is discussed, with particluar reference to the effects of heat, oxidation, cutter and luxing stocks, and emulsification. Acceptance criteria for bitumen emulsions are specified in terms of stability, curing characteristics, and resistance to stripping.
The summary provides volumes of bitumen used annually in New Zealand, applications used for bituminous emulsions, comparison of costs of hot bitumen with those of bitumen emulsions, as well as lists of benefits and limitations of bitumen emulsions. Recommendations for future action include development of a Bitumen Emulsion Sealing Manual in which guidelines for application procedures are established, evaluation of the sand circle method for establishing emulsion applications rates, and development of a test procedure for assessing potential moisture damage. Also included are ways to address the limitations of emulsions and to increase emulsion use in New Zealand.