PREDICTED DESIGN THICKNESS OF MODIFIED HMA LAYER FOR FLEXIBLE HIGHWAY PAVEMENT

Fahem Al-khafaji, Fatimah

	PREDICTED DESIGN THICKNESS OF MODIFIED HMA LAYER FOR FLEXIBLE HIGHWAY PAVEMENT
KUFA JOURNAL OF ENGINEERING
Article 1, Volume 8, Issue 1, 2017, Pages 79-96
Author
Fatimah Fahem Al-khafaji
Abstract
The major reason for using asphalt mixture modifiers is to improve the performance of asphalt pavement to meet the requirement under prevailing stresses from traffic loading and environment effects and to reduce the pavement thickness. Structural thickness design of asphalt pavement layers is a function of many factors; one of the most important of them is the elastic modulus (E) of the asphalt mix. E values may be estimated directly in a laboratory by test, or indirectly by correlation with other tests like Marshall Stability. Additionally, E of hot mixture asphalt is used to estimate the layer relative strength coefficient (a) that is used to estimate the Structural Number parameter (SN), which allows for determining the required layer thickness. The major objective of this research is to predate a statically model to estimate the effect of asphalt modification on the layer thickness. 75 specimens of control and modified HMA for surface are designed and tested according to Marshall Method with optimum asphalt cement content (4.8%) and different types and contents of available modifiers. In order to establish a relationship between the thickness of the surface layer (D) for a flexible pavement and modifier type (MT) with modifier content (MR) in the mix design. The structural model showed a nonlinear relationship between the parameters of the mix design having R2 = 0.7 as shown below: D = ae (bMT) + ce (gMR) (a, b, e, g are constants)
Keywords
Marshal stability; static modulus; Strength coefficient layer; Structural number; Prediction model

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