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Adjustments to the recipe - acoustic optimization potential

Extensive practical experiences were used to optimize the installation parameters of semi-dense asphalts (SDA surfaces) and improve their acoustic effectiveness. 1

The evaluation showed that the variety of mixtures approved in the standard VSS 40 436:2019 / SNR 640 436:2015 leads to significant differences in acoustic quality. It became particularly clear that the installation parameters – especially the Marshall void content, the grain composition (filler and sand content), and the compaction – have a significant influence on acoustic performance.

SDA 4

Optimal void content (MPK)

15%

Range of void content (MPK)

13-17%

Experience values requirements for fine fractions:

- Filler content:
- Sand content:

Additional requirements:
-Sieve 0.5
-Sieve 1mm
-Sieve 4mm


(2*Sieve 0.063+Sieve 2.0) < 42* or 42-47**
6.5 – 8.2% (10%**)
18 – 27% (30%**)


Max. 16%
Max. 20%

Binder

It must be ensured that a binder with a not too low softening point is chosen (≥65°C).

Controlled manufacturing process

It is recommended to test the processes on the plant and to keep the preparation of the mixture as constant as possible to avoid compromising the quality of the mixture. Overheating of the mixture should be avoided to prevent impairing the long-term properties of the binder.

Storage & Transport

Thermally insulated container and suitable discharge technique recommended to avoid segregation

*optimal range
**extended range: additional requirements must be considered

With QuietPave Mix, it can already be recognized in the planning phase whether the asphalt mixture is optimally designed for noise reduction and durability. The web application combines CPX measurements, material data, and AI-supported analyses to enable a scientifically based optimization of SDA 4 surfaces. This can help avoid costly misdevelopments and minimize the risk that a surface does not achieve its desired noise-reducing effect.

The recommendations listed above are based on the current state of research. It should be noted that when examining bivariate relationships in a multivariate and complex environment, achieving a specific target value does not automatically mean good acoustic performance, as other relevant parameters may lie outside the optimal range. On the other hand, there is a high probability that the optimal range of certain parameters can be expanded, provided that another influencing parameter compensates for this and thus the acoustic performance remains positive. G+P AG is committed to further investigating and possibly expanding the limit ranges based on new findings.

1 Steiner, S. et. al. (2022) `Achieving a better match between ordered and actual performance of urban low-noise asphalts – exploring better solutions for noise abatement, Conference Proceedings InterNoise 2022 Glasgow.
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