Asphalt-related temperature correction of deflections measured in central FWD tests on a concrete-over-asphalt composite pavement

ABSTRACT

This study focuses on the seasonal variations observed in five Falling Weight Deflectometer (FWD) tests conducted on a well-instrumented composite pavement. The main objective is to investigate the underlying mechanisms driving these seasonal variations and propose a method to facilitate the comparison of the different FWD tests. The stiffnesses of concrete, asphalt, and cement-stabilised layers are characterised individually. The stiffness of the subgrade is back-calculated using multi-layered simulations. These simulations also enable computation of deflections for different asphalt temperatures. The results allow for developing a method which converts measured deflections into corrected deflections referring to an asphalt reference temperature. Remaining seasonal variations of the corrected deflections refer to the subgrade. Corresponding k-values of the AREA4 method correlate well with seasonal variations of the stiffness of the subgrade. Finally, an alternative temperature-correction approach, requiring measured deflections only, is developed. Corrected deflections allow for quantifying seasonal stiffness variations of the subgrade.

KEYWORDS:

• Field-testing
• multi-layered
• non-destructive testing
• seasonal variation
• composite slabs
• FWD

Acknowledgments

Interesting discussions with Christian Hellmich and Luis Zelaya-Lainez are gratefully acknowledged. Help of Olaf Lahayne, Wolfgang Dörner, Dominic Hassan, Michael Haminger, and Constantin Kreil, as well as David Valentin and Bernhard Hadler (TU Wien) concerning laboratory testing is also gratefully acknowledged. Michael Celadnik and Harald Aigner (Nievelt Labor GmbH, Austria) are also acknowledged for conducting FWD measurements and interesting discussions. The authors acknowledge TU Wien Bibliothek for financial support through its Open Access Funding Programme.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research received financial support by the Austrian Research Promotion Agency (FFG) within the Bridge Project 2021 ‘Grundlegende Analyse von FWD-Versuchen: innovative Experimente, moderne Struktursimulationen, statistische Datenanalyse – FALLINGweight’. The authors also acknowledge the TU Wien University Library for financial support through its Open Access Funding Programme.