Due to the introduction of a limit value for asphalt fumes and aerosols during the paving of asphalt, technical measures on the asphalt paver and a reduction in paving temperatures are required. It must be ensured that the temperature reduction does not impair the mechanical and functional properties or the durability of the asphalt mixture.
The aim of the research project was to develop a uniform method for verifying the temperature reduction using different additives and technologies in the laboratory for use in initial tests, WPK and control tests. For this purpose, specimens were produced at varying temperatures and with increased compaction energy using different compaction devices. Based on the determined bulk densities, compaction functions were derived that can be used to determine both possible reduced compaction temperatures and the required compaction energies.
All relevant technologies for the production of warm mix asphalt (WMA) were investigated, including surfactants and rheology- or reactivity-modifying additives, mineral additives, foamed bitumen technology, and viscosity-modifying additives. The methodology was first tested on an asphalt surface course mix (AC 11 D S) with various additives and compaction methods. In addition, the deformation resistance of the specimens was investigated.
The results show that WMA requires less mixing and compaction work and that a temperature-reducing effect can be demonstrated with all the technologies investigated. The Marshall compaction device proved to be the most suitable for differentiated and reproducible evaluation. Validation on other types of asphalt mixtures, some of which are considered critical – including those with a high asphalt granulate content – confirmed the transferability of the procedure.
Overall, the test system developed enables a comparable and reproducible evaluation of different WMA technologies without having to expect negative effects on deformation resistance.
The project data are presented below:
Funding institution: Federal Highway and Transport Research Institute (BASt)
Project title: Development of a testing system to assure the quality of temperature-reduced asphalt mixtures
Acronym: QTA
Duration: 26 months (1 December 2022 – 28 February 2025)
Project leadership: Technische Universität Braunschweig – Pavement Engineering Centre
Project partner: Universität Kassel (Sachgebiet Bau und Erhaltung von Verkehrswegen)
