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Installing paving synthetics - an overview of correct installation procedures (part one)

Barazone, M.

Paving fabric is a nonwoven permeable fabric used with a bituminous tack coat sufficient to saturate the fabric, turning it into an impermeable moisture barrier with enough residual tack to bond to the old and new asphalt concrete layers. The result is an integrated flexible membrane system. Nonwoven paving fabrics can be manufactured using polypropylene or polyester. PP fabric has more fibre coverage per weight, is slightly more absorbent for oil and is less expensive to manufacture. However, it has low shrinkage and a low melting point. Polyester fabric has greater shrinkage and a higher melting point, making it more resistant to installation damage. There are four types of manufacturing processes for nonwoven fabrics. Specifications may seem to be nearly identical, yet the fabrics perform very different during installation: needle-punched; needle-punched and heat-bonded (calendered), one sided; heat bonded, two sided; resin-bonded. However, only one sided heat-bonded fabrics have all the qualities desirable in a paving fabric. Fabric properties specified by the designer can be tested, usually by ASTM standards. The most commonly specified properties are mass per unit area, Grab tensile strength, elongation, asphalt retention, fabric storage, and heat resistance. It should be noted that improper fabric storage can cause numerous problems. Damage to plastic wrappers allows moisture and UV rays to reach the fabric, breaking down some fibres just in a few weeks. Wet fabrics create steam, which may cause the asphalt to be stripped from the fabric because of a poor bond.