Fracture Behavior of Asphalt Materials by Sadjad Pirmohammad & Majid Reza Ayatollahi

Author:Sadjad Pirmohammad & Majid Reza Ayatollahi
Language: eng
Format: epub
ISBN: 9783030399740
Publisher: Springer International Publishing

Mode of loading

Me

S1, S2, and L (mm)

YI

YII

Pure mode I

1

33, 33 and 0

4.29

0.00

Mixed mode I/II

0.66

33, 13 and 1.5

1.63

0.95

Mixed mode I/II

0.32

33, 13 and 6.5

0.89

1.62

Pure mode II

0

33, 13 and 11

0.00

2.26

In this research [55], fracture tests were conducted under pure mode I, pure mode II, and two different mixed modes of Me = 0.66 and Me = 0.32. In order to perform the fracture tests, the SCB specimens were initially put into a freezer fixed at −15 °C for 6 h to ensure all parts of the specimens have the same temperature. They were then placed upon the bottom supports of the UTM adjusted at the proper locations (i.e., S1 and S2) given in Table 3.4, and the top fixture was finally moved downward at a displacement rate of 3 mm/min to load them. Fracture load Pcr was obtained from the load-LLD curve recorded from the fracture tests. It is notable that the fracture test set-up shown in Fig. 3.6 was used in this study. As mentioned in Sect. 3.2.3, the fracture strength Keff of HMA mixtures can be calculated by putting the values of Pcr, geometry factors (i.e., YI and YII given in Table 3.4), and dimensions of SCB into Eqs. 3.4–3.6.

Figure 3.21 exhibits fracture strength of the Nano Fe2O3 modified HMA mixtures. For all the modes of loading, by increasing the Nano Fe2O3 content in the mixture, the fracture strength firstly increased to reach its maximum value at 0.8%, and then decreased, signifying that there was an optimum value for addition of the Nano Fe2O3 to HMA concrete. Therefore, 0.8% was the suitable value of the Nano Fe2O3 content for adding to asphalt mixtures. Kordi and Shafabakhsh [63] also observed similar results. Based on their study, the addition of 0.9% Nano Fe2O3 to the stone mastic asphalt mixtures showed the best results for the mechanical properties of asphalt mixtures while addition of higher amounts of the Nano Fe2O3 aggravated the performance of mixture. Indeed, the Nano Fe2O3 contributed the binder particles to exhibit higher adhesion features, and therefore, the aggregates were strongly bonded together.

Fig. 3.21Fracture strength of HMA mixtures modified by different percentages of Nano Fe2O3 under different modes of loading [64]

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