Research needs

The project addresses the acoustic performance and mechanical durability needs of low noise semi-dense asphalt in Switzerland, addressing the priority two priority research focuses of ASTRA «TRU 1 - Erhöhung der mechanischen Dauerhaftigkeit und Lärmreduktion von Belägen» as well as «TRU 3- Alterung von Bitumen: Mikrostruktur sowie chemische Zusammensetzung». .

Research objectives

Improving the acoustic and mechanical durability of Semi Dense Asphalt, SDA 8, SDA 6 and SDA 4, by optimizing and adapting the mixtures to different traffic and climatic conditions present on the Swiss national and main road network using a multi scale approach.

Methodology - the multi-scale optimization approach

The unique multi-scale optimization approach proposed herewith by Empa, G+P and IMP utilizes the advantages of laboratory testing at different scales and connects the improved durability char-acteristics of low-noise SDA to their performance on real roads. An overview summary is provided in Figure 1. In a first step, 3 SDA mixtures with different maximum aggregates sizes, SDA 4, SDA 6 and SDA 8 are characterized by their multi-scale mechanical and volumetric properties in the lab (WP 1). Simultaneously, a significant amount of data will look at their long-term performance on Swiss roads (WP 2), identifying the key parameters for the long- term acoustic performance. The next phase consists of an optimization cycle that is undertaken at the mastic and then mixture lev-els (WP 3). The mastic optimization will consist of rheology testing while the mixture optimization will look at water sensitivity, modulus and other mechanical and microstructural properties. WP4 will subject the optimized samples from WP3 to largescale durability testing using the traffic load simu-lator MMLS3, combined with acoustical testing and acoustic modelling. The optimizations will be translated into expected improvements regarding the acoustic and mechanical durability of low-noise SDA on real roads.

Research outcomes & expected benefits

The outcome of the proposed project will provide the basis for an improved durability of low-noise SDA which can be directly applied by the industry and incorporated in national standards.

Project Period:

2021-2023