Warm mix asphalt-a German case study

In Germany, warm mix asphalt (WMA) is not commonly used although this technology was initially introduced to the practice between the 60s and the 80s. The current guidelines are devoted to the reduction of the mixing temperature for mastic asphalt (MA) (Gussasphalt). Due to this requirement, a number of products consisting of plain or polymer modified binder premixed with additives such as wax are available on the market. However, a well-established set of regulations addressing the production process and performance parameters is not available as in the case of conventional hot mix asphalt (HMA). For this reason, a case study which aimed to address the effects of viscosity changing additives (waxes) on asphalt mixture properties was conceived. In this large experimental study, three different additives (waxes) were used. First, the impact of waxes on asphalt binder properties and the corresponding rheological response were evaluated. Then, performance tests, such as rutting resistance tests, fatigue tests, and low temperature behavior tests, were conducted on asphalt mixtures AC 11 B S and AC 16 D S prepared with plain and polymer modified binders. No significant reduction in compaction temperature was observed when waxes were incorporated in the mix design. All additives were capable of improving rutting resistance, while poorer low temperature performance was exhibited. Based on the experimental campaign, the use of waxes could be recommended only to facilitate mixing.