Comparison between resilient modulus and dynamic modulus of Western Australian hot mix asphalt based on flexible pavement design perspectives

The modulus of asphalt concrete material is one of the major input parameters in mechanical-empirical pavement design and analysis. In Australia, current pavement design approaches rely on the resilient modulus of the asphalt material, and visco-elastic behaviour cannot be incorporated into this pavement analysis and design. However, in the USA, the NCHRP 1-37A design guide for Mechanistic-Empirical pavement design (ME design) uses the dynamic modulus to express the intrinsic behaviour of this important input parameter, i.e., the visco-elasticity of an asphalt material, over a range of temperatures and loading frequencies. This study aims to examine whether the dynamic modulus which is converted from a resilient modulus test is different to the resilient modulus when considering as a modulus input for pavement design. Three different asphalt concrete mixes, with varying maximum aggregate sizes of 7, 10, and 14 mm were selected as mix representatives. All test specimens were controlled using a - gyratory compactor to produce a 5% air void. To determine the resilient modulus and the dynamic modulus respectively, a UTM-25P and an Asphalt Mixture Performance Tester (AMPT) were used. In addition, pavement design exercises were performed on pavement structures typical to Western Australia. The exercises evaluated the difference of tensile strains at the bottom of asphalt layer derived from the different input parameters of the resilient and dynamic moduli

An investigation into Dynamic Modulus of Western Australia Hot Mix Asphalt

Most road networks in Western Australia (WA) are made of flexible pavement with a relatively thin asphalt wearing course and Dense Graded Asphalt (DGA), a commonly used asphalt mix with a continuous size distribution and a low design air-void of around 3% to 7%. Currently, the input parameters for asphalt material for pavement design in Australia still rely entirely on the resilient modulus which cannot incorporate the visco-elastic behaviour of such material into pavement analysis and design. Unlike the resilient modulus, the recently introduced parameter of the dynamic modulus can express the intrinsic behaviour of the visco-elasticity of an asphalt material. The dynamic modulus can describe the stress-strain relationship of viscoelastic material across a wide range of temperatures and frequencies in the form of the Master Curve. The Master Curve is constructed from a sigmoidal function and the Time-Temperature Superposition principle (TTS) with a second-order polynomial shift factor function, according to AASHTO PP62-09. This study aims to investigate the dynamic modulus of Western Australian asphalt mixes, considering three different mixes with varying maximum aggregate sizes of 7 mm, 10 mm, and 14 mm. For this study, all test specimens were controlled to reach a 5% air-void with a Survopac gyratory compactor. Specimens were then tested with an Asphalt Mixture Performance Tester (AMPT) with a testing range of four temperatures: 4°C, 21°C, 37°C and 54°C, and six frequencies; 0.1 Hz, 0.5 Hz, 1 Hz, 5 Hz, 10 Hz, and 25 Hz, according to AASHTO TP62-07. Moreover, the dynamic modulus predictive equation proposed by NCHRP 1-37A MEPDG was modified and introduced to suit WA asphalt mixes

Clay-cement additive for crushed rock base stabilisation: Strength property investigation

With the current base course material in Western Australia, namely hydrated cement treated crushed rock base (HCTCRB), roads using HCTCRB require excessive maintenance causing from its uncertainties. This study aims to determine specific strength properties of a potential replacement material of a clay - cement stabilized crushed rock. The findings showed that a crushed rock material with a newly developed 3% clay - cement binder, possessed unconfined compressive strengths and resilient moduli significantly greater than that of HCTCRB . The developed stress dependent equation also purports that this material admixture is still exhibiting unbound performance characteristics. A material’s ability to acquire the accompanying strength advantages of a 3% clay - cement binder, whilst still potentially resisting common failure methods such as shrinkage cracking, suggests that based on its potential performance as a base course layer in a pavement structure, clay - cement stabilized crushed rock base is considerable to be a viable base course material for Western Australia