Solvent-free WPK

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Quality assurance of asphalt without solvents - development of alternative procedures for the performance of the WPK

The quality of asphalt as a construction material is monitored by the asphalt manufacturer as part of the factory production control (FPC). The composition of the asphalt mixture is checked by separating it into its basic materials bitumen and aggregates using a solvent. In addition to the binder content and the composition of the aggregates, the bitumen recovered from the mix is examined. For extraction and recovery, the carcinogenic trichloroethylene is mostly used, for which there will be restrictions on use in the future under the EU REACH regulation.

The aim of the research project is to develop a quality assurance procedure for use in the WPK, in which no solvent use is required. For this purpose, the composition of the asphalt mixture is to be determined by means of thermal analysis through ashing of the organic binder. The grain size distribution can be determined on the remaining aggregates. 

Simple mechanical tests on asphalt test specimens will be used to draw conclusions about the bitumen used and possible changes during asphalt production (e.g. inadmissible hardening) as well as the effectiveness of additives used. The selection of the test methods is based on the achievable test precision (repeatability), the availability of the required test equipment in the WPK laboratories and the time required until the test results are available.

The use of alternative solvents is associated with high investment and running costs, which represent a major burden, especially for small and medium-sized asphalt producers and laboratories carrying out the WPK. By converting the WPK to solvent-free test methods, these costs can be significantly reduced and an important contribution made to occupational health and safety.