Evaluation of Witczak E* predictive models for the implementation of AASHTOWare-Pavement ME Design in the Kingdom of Saudi Arabia

Comparison of Witczak NCHRP 1-40D & Hirsh dynamic modulus models based on different binder characterization methods: a case study

“…The researchers reported that the NCHRP 1-37A model with level 3 binder input produced the most accurate and least biased E* predictions compared to the other levels of binder input and the NCHRP 1-40D model at all three binder input levels [10]. Similar results on mixes from the Kingdom of Saudi Arabia (KSA) were also reported by Khattab et al [5]. Thus, based on the multitude of the literature research studies covering the presented E* models, one may surmise that the prediction accuracy of these models is not consistent and vary depending of the properties of HMA and binders.…”

“…A total of 25 KSA mixes were investigated. The investigated field mixes cover the different climatic regions of KSA (i.e., central, northern, southern and, eastern regions of KSA) [5,22]. The mixtures contain14 laboratory mixes and 11 plant-produced mixes that were collected from ongoing road construction projects in KSA.…”

“…where: log log િ = ‫ܣ‬ + ܸܶܵ log ܶ ோ (5) where: Ș ELQGHU YLVFRVLW\ LQ FS 7R= testing temperature, in Rankine; A= regression intercept; and VTS= viscosity-temperature susceptibility (regression slope of the viscosity-temperature relationship).…”

“…On the other hand, Hirsh model under-predicted E* values while Bari and Witczak model over predicted E* values. The researchers also reported that the large bias in the estimated E* values of Greece mixes using Bari and Witczak or the NCHRP 1-40D E* models is due to the associated equations used for the estimation of G* DQG į ZKLFK LQ PRVW FDVHV GLG QRW \LHOG DFFHSWDEOH YDOXHV > @ Few studies focused on the investigation of the effect of binder characterization input level, as per Pavement ME Design or MEPDG, on the prediction accuracy of the E* models [5,9,13]. Other studies evaluated the effect of the MEPDG binder input level on both Witczak E* predictive models based on 27 Idaho asphalt mixes [9,13].…”

“…Consequently, over years, researchers have tried to establish E* predictive models using a number of laboratory E* databases. The most well-known models are the ones developed by Professor Witczak and his students over the last few decades [3][4][5]. Hirsh model is another well-known model for E* prediction [6].…”