Table of Contents

7.3.1 Primes

Curing time

Initially, the primer should be allowed to dry and cure, or thicken and increase in viscosity (by evaporation of cutter oil), or in the case of emulsions ‘break’ before any trafficking is allowed.

A surface primed with cutback bitumen should be allowed to cure for a minimum period of three days prior to sealing, depending on prevailing drying conditions. Cutter can be trapped in the prime if sealed over too early and will diffuse into the seal and soften it.

Bitumen emulsion and some proprietary primers (specialty grades) can often be sealed after one or two days curing, depending on prevailing drying conditions. Caution should be taken to verify this shorter curing period is adequate for the particular product and prevailing conditions before use.

Expected lifespan

A prime can be expected to have an untrafficked lifespan of several weeks, without further treatment other than normal maintenance, if an appropriate prime grade and application rate are used. Trafficking has the potential to reduce the lifespan of a prime and should be minimised.