Asphalt Interlayer Composite

Storage and surface preparation - Store and transport rolls flat and dry between −30°C and 80°C at no more than 85% relative humidity, covered and away from mud, wet concrete or asphalt. Before laying, the pavement must be clean, dry and free of dust, debris and organic matter - wire brush and tractor-mounted air compressor. Seal cracks wider than 6 mm with an approved sealant or a levelling course mix. Potholes, surface failures and heavily cracked sections must be repaired as directed by the supervising engineer. Surface temperature must be between 5°C and 60°C; do not proceed outside that range.

Tack coat - Apply 0.6–1.0 kg/m² of residual bitumen, using hot-applied bitumen or bitumen emulsion as the project requires, adjusted for surface roughness, temperature and base layer absorption. Distribute evenly, avoiding overspray and missed areas, and extend the coating 75 mm beyond every edge of the composite. With emulsion in warm conditions, placement may begin almost immediately; in cooler conditions wait until the emulsion fully breaks from brown to black. With hot bitumen, place the composite immediately for best saturation. Do not apply tack coat or install during rainfall or when rain is expected.

Placement - Lay the composite with the nonwoven face in direct contact with the tacked surface, running in the direction of paving. Mechanical laying with a purpose-built laydown frame or a vehicle-mounted roller system is preferred, keeping continuous tension on the roll to avoid wrinkles. For manual laying, unroll onto the tacked surface and press the grid down firmly with a stiff broom or wire brush to achieve full contact. On constrained or curved sections use shorter lengths to reduce misalignment.

Joints and wrinkles - Transverse joints overlap 75–150 mm with the top layer aligned in the direction of the paver's travel so it cannot lift. Longitudinal joints overlap 25–50 mm. Leave a 50–100 mm gap from pavement edges to prevent capillary water ingress. Apply additional tack coat over every overlap. Where wrinkles or wrap-ins occur, cut along the centre of the wrinkle, lay each side flat and secure with extra tack coat or mechanical fastening. If nailing is required, use washers larger than the grid aperture.

Rolling and adhesion check - Allow 20–30 minutes after placement, then roll with a pneumatic tyred roller to remove wrinkles and improve bond, applying vegetable oil to the tyres to prevent lifting. Where traffic over the exposed composite is unavoidable, restrict to 5–10 km/h with no sharp turns, sudden braking or stationary wheel turning. Before paving, verify adhesion: hook a calibrated spring balance into the centre of the laid composite and pull vertically until four to five apertures lift on all sides. Proceed at 9 kg or above; below that, stop and investigate - poor adhesion is usually surface contamination from water or debris.

Paving - Paving may begin only once the tack coat is fully cured and the composite is firmly adhered with minimal lifting or displacement. Protect the laid composite from asphalt delivery trucks with a light cover of 8–12 mm stone chips or a thin asphalt layer over the grid. Feed mix beneath the paver with a shovel rather than allowing it to push the composite. Do not use plant with worn or damaged tyres. Any displacement or damage before or during paving must be repaired or replaced immediately before the overlay continues.