Table of Contents

3.2 Initial Treatments

An overarching term ‘initial treatment’ is used to describe spayed seal treatments applied directly onto newly constructed and prepared pavements.

Using an initial treatment usually results in a choice between applying a prime (Section 3.2.1) followed by a seal or by applying an initial seal (Section 3.2.2) followed by a seal within one to two years. Table 3.1 provides a summary of the advantages and disadvantages of both options.

Table 3.1: Advantages and disadvantages of initial seals, and prime and seals

Initial treatment typeAdvantagesDisadvantages
Prime and seal
  1. Generally more economic in overall cost.
  2. Reduced absorption of seal coat binder into the pavement.
  3. Thicker waterproof layer.
  4. Strong bond to the pavement.
  5. May be used to protect pavement prior to sealing.
  6. Easier to cope with non‑uniform pavement condition and texture.
  1. The pavement surface must be dry.
  2. Best results are obtained in dry/warm conditions.
  3. Two-stage process.
  4. The primer must be dry and cure before sealing. A prime requires at least 3 days to cure without trafficking.
  5. Use of pavement by traffic is restricted.
  6. Rain may cause uncured primer to be washed off the pavement with loss of primer and risk of environmental damage.
Initial seals
  1. Can be placed on a damp pavement.
  2. One-step process that can be opened to controlled traffic once completed.
  3. Allows repair of pavement deficiencies prior to final seal.
  1. Relatively short-term treatment and should be followed by a secondary seal to complete the treatment within 1 to 2 years.
  2. Cutback bitumen initial seals require 3 to 12 months for cutter to dissipate.
  3. Rain soon after pavement construction can lead to problems such as aggregate embedment, binder emulsification, stripping of aggregates and binder pick‑up by vehicles.