Federal Highway Research Institute


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Reduced-temperature asphalt design

Reduced-temperature asphalt is manufactured and processed at a temperature 20°C to 30°C lower than the level commonly selected at present. For reasons of compressibility and processability, manufacturing temperatures for conventional asphalt usually lie near the maximum limit stipulated by ZTV Asphalt-StB.

The photo shows asphalt installation Asphalt installation

The objective behind developing reduced-temperature asphalts was a reduction in CO2 emissions and the accompanying benefit of lower energy consumption. Moreover, the hazardous substances committee in 2000 re-defined limiting values for vapours and aerosols arising during high-temperature processing of bitumen. So far, two options of lowering asphalt temperature have been developed and successfully tested: Mineral additives and viscosity-altering organic additives.

Previous experiences with reduced-temperature asphalt were made on test routes with a laytime of several years. A conclusive evaluation of the technical properties of asphalts manufactured and processed using mineral or organic additives at reduced temperatures is only possible after a utilization period of roughly 15 years. Many of the test routes are established and monitored by the Federal Highway Research Institute.