Dipentene (a solvent derived from radiata pine) and toluene were investigated as alternatives to the ozone-depleting methyl chloroform used in bitumen content determinations of asphalt. Toluene was also considered as an alternative to trichloroethene used in the determination of bitumen solubility, as specificed in Transit New Zealand Specification M/1.
It was established that dipentene cannot be used as a substitute for methyl chloroform, but that toluene could be, and without making any changes to the experimental procedure given in ASTM D2172 or the commonly used 'Auckland method'. Toluene is less environmentally harmful approximately the same price, and slightly less toxic than methyl chloroform. However, toluene is highly flammable and suitable precautions must be followed when large quantities are being handled in bitumen content determinations.
Toluene can also replace trichloroethene in the measurement of bitumen solubility. Although the specification limits given in Transit New Zealand M/1 do not need alteration, a small change is needed in the experimental procedure, in which case the method given in Transit New Zealand M/1 needs to be changed from ASTM D2042 to the Australian Standard Method AS 2341.8.
Keywords: Asphalt, bitumen, methly chloroform