Predicting Oxidative Age Hardening in Asphalt Pavement with Time and Depth: A First Approximation Michael J. Farrar (mfarrar@uwyo.edu) Will Grimes Fred Turner P. Michael Harnsberger Shin-Che Huang P3 Symposium Laramie, Wyoming July 14, 2011
Rochester, MN comparative test site Core collected 2008 Project constructed 2006
4 mm diam. parallel plate DSR Published reports 25 mg sample Sui, C., M.J. Farrar, W.H. Tuminello, T.F. Turner, New Technique for Measuring Low-Temperature Properties of Asphalt Binders with Small Amount of Materials, TRB January 2010, Washington, D.C. SiC Sui, C., MJF M.J. Farrar, PMH P. M. Harnsberger, WH W. H. Tuminello, T. F. Turner, A New Low-temperature Performance Grading Method Using 4 mm Parallelplates on a DSR, TRB January 2011, Washington, D.C. Draft modified AASHTO method 4 mm dia. parallel plate DSR with machine compliance correction AASHTO T315 Determining the Rheological Properties of Asphalt Binder Using a Dynamic Advantages: Shear Rheometer Instrument compliance correction Working on Low and intermediate temp. rheology Small sample (25 mg) Rapid alternative to AASHTO T313 (relaxation test Low heat req. (<60C) (5 minutes) at the low PG temperature + 10 C.
MN1 3 2 nd slicee* at t = 2 and t = 0 years Ext. binder DSR Al-Khateeb et al., AAPT, 2007)
MEPDG E* models [Bari and Witczak, AAPT, 2006] [Bari and Witczak, AAPT 2006]
E* GAS application Global Aging System models NCHRP 1-37A Material Characterization, Design Inputs (2.2.13) (2.2.11) (2.2.7)
MEPDG compared to extraction
Laboratory aging data for a first approximation 3 Aging times RTFO RTFO/PAV (100 C C, 20 hours) RTFO/PAV (100 C, 48 hours) 4, 8, and 25 mm dia. parallel plate DSR
SAT Aging scheme and rheology Long term aging convection oven atmospheric pressure SAT(40 0hours, 100 C) ~ Std. Sd PAV DSR Low, intermediate and high temperature rheology (4, 8 and 25 mm dia. parallel plates). Multiple stress creep recovery test (MSCR). Linear amplitude sweep test (LAST). Short term aging convection oven atmospheric pressure SAT(50 minutes, 150 C) ~ RTFO SAT(50 min., 130 C) ~ WMA? Long term aging (Pressure aging vessel) SAT(8 hours, 100 C) ~ Std. PAV
Applied Models Christensen, D. W. and D.A. Anderson Interpretation of mechanical test data for paving grade asphalt cements. Journal of the Association of Asphalt Paving Technologists, vol. 61, 67-116, 1992. Brown, A. B., J. W. Sparks, and O. Larsen. Rate of Change of Softening Point, Penetration, and Ductility of Asphalt in Bituminous Pavement. Journal of Association of Asphalt Paving Technologists, Vol. 26, 1957, pp. 66-76. Global Aging System models NCHRP 1-37A Material Characterization, acte at Design Inputs
Evolution of the CA Model parameters
First Approximation
Comparison: Extraction, MEPDG, 1 st approximation
Conclusion This presentation demonstrates an approach to estimate mix dynamic modulus (E*) at any time or depth in the pavement. The approach presented here involves the evolution of the Christensen-Anderson (CA) model parameters with oxidative aging.and, in addition to E*, other binder and mix mechanical properties can be estimated: Binder: SHARP specifications : G*/sin δ, G* sin δ, m-value, S(t) Binder and Mix: Thermal stress build up (σ T ) Binder ductility G /η /G ) The application of the Global aging system (GAS) models in the analysis may cause significant error since using an average temperature such as the mean annual air temperature (MAAT) does not take into account the heavy weighting of the reaction rate at higher h temperatures. t The GAS was only used here to obtain a first approximation of E*. Work is underway to apply a two step aging scheme (a short term first order reaction and a long term zero order reaction) to more accurately estimate the time evolution of the CA model parameters.
Questions?