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