Field Verification of Superpave Dynamic Modulus
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Date
2010-05Author
Gedafa, Daba S.
Hossain, Mustaque
Romanoschi, Stefan
Gisi, Andrew J.
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In the mechanistic-empirical pavement design guide, prediction of flexible pavement response and performance needs an input
of dynamic modulus of hot-mix asphalt at all three levels of hierarchical inputs. This study was intended to find the best way to
predict/derive this input. Nine Superpave pavement sections were selected as test sections in this study. Deflection data on all test sections
was collected with a Dynatest 8000 falling weight deflectometer shortly after construction. The deflection data, normalized with respect
to 40-kN load, were used to back-calculate asphalt layer moduli using three back-calculation algorithms. Laboratory dynamic modulus
tests were conducted on asphalt concrete AC cores and laboratory-compacted samples. Dynamic modulus was also estimated with the
Witczak model, new Witczak model, and Hirsch model. The results show that the AC moduli obtained from various back-calculation
programs used in the study are generally comparable. Laboratory dynamic modulus is comparable at 4°C, but the variation increases as
the test temperature increases. The Witczak model underestimates the dynamic modulus at low temperature and overestimates it at higher
temperature. The parameter estimate when the laboratory dynamic modulus is used as a dependent variable and the moduli from other
approaches as independent variables is close to 1. This is especially true for the AC moduli estimated by various prediction methods. The
Hirsch model appears to be the best for estimation and is closely followed by the new Witczak model.