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powder is also an expensive process that must be taken into consideration. The

components of the asphalt must be carefully controlled and the temperatures closely

monitored, else the quality of the asphalt will decrease substantially (Rubber

Pavements Association, 1998). According to the Rubber Pavements Association there

are five issues that prevent rubber asphalt from gaining wide acceptance:

  • 1.

    Formerly a patented process prevented industry development. Last patents expired in 1992.

  • 2.

    Long held in "experimental" status.

  • 3.

    "If it ain't broke, don't fix it" mentality. Many state highway departments prefer to use old materials and methods.

  • 4.

    ISTEA mandate for use caused political fallout. RPA does not support mandates. A-R should be used by free choice based on its superior qualities.

  • 5.

    "Impostors" (processes with non-reacted rubber additives) often lead to failures associated with A-R. F. Some specialized equipment is required.

(Rubber Pavements Association, 1998)

Rubberized asphalt roads may be a viable option for Hong Kong. The

significant number of tyres used in the process could make a significant contribution

towards the goal of reducing tyre waste.

2.2.4 Pyrolysis

Pyrolysis is a unique method for recycling tyres. The process is

essentially heating without the presence of oxygen, and when performed on complex

organic materials pyrolysis will break the material down into such things as oil, char,

and gases. Laboratory research has shown that when applied to a tyre the process has

the potential to produce approximately one gallon of oil, seven pounds of char, three

pounds of gas, and two pounds of steel and ash (Clark, Meardon, & Russell, 1993).

Due to the complexity of the process, there are many unresolved issues.

Technologies have to improve to increase the efficiency of the pyrolysis process as

well as the processing of the products. According to the EPA, there are no pyrolysis


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