Primes and primerseals are designed to achieve an appropriate amount of penetration into the compacted basecourse surface to prevent lifting or peeling of subsequent seals. The RTA Sprayed Sealing Guide recommends 5-10 mm of penetration for primes and 2-5 mm for primerseals. Penetration requirements are usually met without difficulty in unbound basecourse materials, especially when cutback bitumen is used as the primer or primerbinder. However, difficulties have been experienced in achieving the required penetration into bound pavements. In response to this, a series of laboratory tests was conducted to investigate the penetration of both cutback bitumen and emulsions into a range of bound basecourse materials used for the construction of pavements throughout NSW. Also investigated was the effectiveness of an artificially penetrated layer, created by physically mixing emulsion with the upper surface of the basecourse material. This paper summarises the work carried out to develop an appropriate laboratory compatibility test for priming and primersealing work which can be used to determine the type of primer or primerbinder and the approximate application rate to be used for a particular basecourse material. It also summarises the comparative performance of cutback bitumen and bitumen emulsion. (A)
Abstract