In addition, Polymer Modified Mastic Asphalt (PMMA) complying with A2.5.1 and A2.5.2 may be used. This material is a flowable asphalt and typically used around ironwork. No compaction is needed, so demonstrating compliance with S10 is not necessary.
PMMA may be used as bedding, backfill or surfacing material as specified in the following clauses. PMMA must be used within the stated location and limitations (including maximum width of the reinstatement) as detailed in the Product Acceptance Scheme certificate.
When PMMA is used, Installation and Quality Control Procedures for all systems must be in accordance with an approved certificate from a Product Acceptance Scheme for each system, and with the current method statement. Quality assurance information and the results of all quality control checks carried out on site by the undertaker must be compiled in accordance with the requirements of the certificate.
Before installing any bedding, backfill or surfacing material, the receiving surface must be free of loose material and the area must be free of debris, oil, grease, dust or other visible contaminants. All exposed edges and joints must be primed to achieve a proper bond with the existing surface (see S6.8).
Installation of PMMA can only be carried out in dry conditions at a temperature above -5ºC, unless otherwise stated in the product certification.
Ambient and road surface temperatures, including maximum and minimum temperatures, must be recorded during the installation process for future reference in the relevant street works notice or permit.
PMMA can be supplied in block form for re-melting on site or in molten form in purpose-built hot charge transporters. All heating equipment must be suitable for re-melting or transporting the material as appropriate and must be capable of maintaining the mix at the manufacturer’s recommended temperature.
The PMMA must be placed into the reinstatement leaving a smooth finish with no gaps. The PMMA is left to stiffen and is assessed in accordance with the method of installation detailed in the Product Acceptance Scheme certificate.
All exposed edges and joints must be primed to achieve a bond with the existing surface.
PMMA must be applied in lifts of 30 to 50 mm thick, and within the manufacturer’s recommended temperature range. It must be spread to finish flush with the surrounding surfacing.
PMMA must be finished with a suitable treatment to provide the necessary skid resistance. This may be 6, 14 or 20 mm bitumen coated chippings or 1 to 3 mm calcined bauxite to the specified PSV. These treatments are applied directly to the hot material and when suitably cooled, lightly rolled or tamped to ensure adequate embedment. For footways only, hard stone grit or a stippled roller may be used as an alternative to chippings or bauxite to provide texture for skid resistance purposes.
PMMA must be allowed to cool to ambient temperature before opening to traffic, as specified in the Product Acceptance Scheme certificate. During the cooling period no disturbance or trafficking of the system is permitted. Assisted cooling during the installation by means of industrial fans may be required. The curing period must be adjusted for the prevailing weather conditions.
Excess aggregate must be removed at the end of the cooling period but before opening to traffic.