Stress Absorbing Membrane Interlayer

  • • Inhibits the reoccurence of a crack in an overlay
  • • Laid prior to resurfacing
  • • Can be driven on by site traffic
  • • Seals the surface against water ingress

Asphalt overlays need protection from the shortcomings of the surface upon which they are laid. All too often, the life of the new asphalt is greatly reduced by the cracks propagated from the joints or faults in the underlying surface. This then allows water and salts to penetrate and the rapid deterioration of the surface asphalt begins.

It is becoming increasingly common for an anti-crack membrane to be installed before laying new asphalt to reduce this problem.

Causes of cracking

Cracks in the highway emanate from either;

  1. The surface, where the surface course is fatigued by the traffic
  2. The sub-base, from movement of the underlying layers

Stress Absorbing Membranes are used when reflective cracks are showing through from layers below the surface, known as reflective cracking.

Whether the wearing course layer is removed and replaced or simply overlaid, movement in the sub-layers which created the cracked surface in the first instance will, without some form of treatment, create new cracks in the new surface. This cracking will propagate at a rate of approximately 1 year for every 25mm of wearing course applied.

Treating the cracks with a Stress Absorbing Membrane prior to overlay, provides the following benefits:

  • • Seals the cracks against further water ingress
  • • Bridges the crack, shifting the concentration of movement across a larger area, minimising its impact
  • • Increases the time until reflective cracks will show through the new surface
  • • Keeps water out of the sub-structure for longer

Jointmaster SAMI (Stress Absorbing Membrane Interlayer)

Jointmaster is a polymer modified, rubberised bitumen compound containing glass fibre reinforcement. The compound is applied as a molten screed directly over the cracks and joints in the surface prior to being overlaid. It fills and seals the cracks in one pass, leaving a membrane focused solely at the point where the movement is concentrated.
This systems offers savings over full surface membranes as the material is laid only at the points where the movement is causing an issue.

  • • Full supply and apply contracting service
  • • Selectively treats just the cracks and joints, not the whole surface
  • • Proven to significantly reduce the occurrence of reflective cracking
  • • Able to be trafficked by site traffic
  • • Provides a watertight seal
  • • Fast installation, up to 500 lin.m achievable in a shift
  • • Can be applied throughout the year
  • • Applied in recommended widths of 200mm for longitudinal cracking and 300mm for transverse
  • • Treatment applied at 5mm thickness when overlaying with 75mm of new asphalt
  • • Treatment rebated into the surface by 10mm or 20mm for thinner overlays