Characterization of Permanent deformation Mondher Neifar, Hervé Di Benedetto, Berthe Dongmo Berthe-Julienne DONGMO-ENGELAND NABin Conferense october 2004.

2 l Evolution in the production of bitumen Rutting in France: milestones Apparition of rutting The problem is solved Rutting reappears l Evolution of axle loads configuration …

3 Bituminous layers Origins of rutting in bituminous roads Arase de terrassement Plate –forme support de chaussée Accotement Partie supérieure des terrassements  1m Roulement Liaison Base Fondation Couches de surface Couches d’assise Couche de forme Sol support Unbound layers 15 to 50 cm

4 l Homogeneous test  rheological model l Measure both “large” (10 -2 ) permanent deformation and “small” (10 -6 ) cyclic deformation  complex modulus Aim

5 Triaxial test on bituminous mixes Test developed h=12cm d=8cm

6 Triaxial test on bituminous mixes l High resolution l A mechanical system to move axial targets Test developed l Temperature regulation

7 Stress path history

8 Type of loading Cycles & rest periods   max t

9 1 Great strain evolution Possible to obtain Complex modulus 0<t<2  /fr Experimental Cycle N & N+1

10 Compression and tension type tests Experimental   max t T = 25°C;  max = 0,4 Mpa; f = 1Hz Stress Time (s) Rest periods Cyclic loading periods

11 0.3% Cumulated number of cycles T = 25°C - f = 1 Hz  max = 0,4 MPa Strain-number of cycles Experimental T = 25°C;  max = 0,4 Mpa; f = 1Hz

12 Phase I Phase II Phase III General curve for continuous loading   max t Experimental  Information in the linear domain (LVE) Small strain measured T = 35°C;  max = 0,4 Mpa; f = 1Hz

13 Tests CompressionExtension 3 temperatures15°C, 25°C and 35°C 2 temperatures15°C and 25°C 3 stress amplitudes 0.1 MPa, 0.2MPa and 0.3MPa 2 stress amplitudes 0.05MPa and 0.1MPa 2 frequencies1Hz and 10Hz1 frequency1Hz l 0/14 Bituminous mixes l 35/50 bitumen at 6.8 ppc

14 Results

15 Influence of frequency Experimental Stress Time (s) T = 25°C  max = 0,4 MPa VEL or classical VP laws not adapted

16 Experimental Tests in compression

17 Phase 3 Type :  = f(N)  0 Frequency Temperature Stress level Experimental Cyclic compression tests  norm = 58.59N  perm = f(  j max )

18 CompressionTraction Volume variation Tension Compression

19 Complex modulus evolution f = 1Hz  max = 0,4 MPa

20 Conclusion l New test  Permanent deformation  Small cycle properties l Results for compression and extension tests l Classical laws not adapted  Cyclic effect l Suitable developments  Prediction

21 THANK YOU

Modelling