Abstract:
Appropriate and cost-effective design techniques are the two things highway agencies are mainly focusing on, and for this very reason RAP is being used for the last two decades. Like other countries, it is also utilized in Pakistan to a great extent. Also, in HMA, normally there is a trend of sing hydrated lime as a mineral filler or anti-stripping additive. In fact, many agencies are using it on high volume road ways. Many researches have concluded that relatively lime mixed with HMA mixtures have longer service life. The dynamic modulus plays an important role in MEPDG software as it has been used as a main design input for designing flexible Pavement. The dynamic modulus is considered as a key parameter of material characterization in mechanistic-Empirical (M-E) design. It correlates the material properties to field fatigue cracking and rutting performance. In this research the dynamic response and fatigue behavior of the samples having different percentages of RAP with lime and mixed with virgin hot mix asphalt (HMA) has been investigated. Marshall mix design was employed for the OBC and Super gyratory samples were prepared and tested for Dynamic modulus, flow number and flow time. These tests were performed using AMPT and were conducted on 4 different temperatures (4.4, 21.1, 37.7, 54.4) C and six loading frequencies (25, 10, 5, 1, 0.5, 0.1) Hz. From corresponding frequencies, the |E*| and P.A values were reported. Dynamic modulus master curves were produced using excel solver. The Results revealed that with increase in temperature the dynamic modulus values decreases. Temperature and frequency were found to be the main variable which significantly affects the dynamic modulus values. Fatigue parameter was calculated using the dynamic modulus and phase angle values and the results revealed that fatigue parameter value is low for Virgin HMA mixtures with 60/70 binder which means that Virgin mixtures are less fatigue susceptible. Flow number and flow time results were also analyzed to determine the rutting susceptibility of mixtures. RAP and lime modified mixtures were found to be less susceptible to rutting because of their stiff nature. The accumulated strains are less, and dynamic modulus values are higher, as compared to the other mixtures which are used in this research study.
