ABSTRACT
ABSTRACT: Minimizing fumes and emissions has become one of the main goals during the laying of bituminous coatings. The first priority is of course to avoid overheating the binders during storage and laying. Warm mix processes have also been developed in many countries in order to lower laying temperatures. However, the question that arises is how would it be possible to predict the environmental impact from laboratory experiments? This study uses headspace gas chromatography to characterise the propensity of bitumens to emit volatile compounds. The target substances were Volatile Organic Compounds (VOC) and Polycyclic Aromatic Hydrocarbons (PAH). This technique involves heating a sample in a sealed vial, which causes the volatile compounds to diffuse into the gaseous phase, or headspace, above the sample. At steady state, a gaseous phase aliquot taken using a specific type of syringe is injected, with a carrier gas, into the separation column where the different molecules are separated from each another. On exiting the column, these molecules enter the mass spectrometer detector. Each signal is shown as a peak on the resulting chromatogram. The chromatogram plots the intensity of the emitted signal (μV) against the retention time (min). The chemical composition for each peak is easily identified from the mass spectrum profile. Quantification is also possible. Experiments have been carried out on a wide variety of pure bitumens with several penetration grades and various origins. The technique was used to analyze different types of fluxes, fluxed bitumens, as well as synthetic and vegetable binders. The samples were incubated at different temperatures up to 180-200°C. The conclusions concerning environmental performance include the following:
• Incubation temperature has a very major impact on VOC emissions. • The origin of the bitumen may be responsible for major differences. • There is a clear benefit to using lower mixing temperatures.
