Permanent deformation of ASPHALTIC materials has a major contribution to rutting. Under static loading, the steady-state deformation of ASPHALTIC materials is the key component of the permanent deformation. The steady-state deformation behaviour of a standard 70/100 penetration grade pure bitumen and two types of ASPHALTIC MIXTURES used in the UK pavements, namely a 10mm Dense Bitumen Macadam (DBM), which is a dense graded mixture, and a 30/10 Hot Rolled Asphalt (HRA), which is a gap graded mixture have been studied. Using Dynamic Shear Rheometer (DSR) Constant stress creep tests were conducted on the bitumen at 10oC and 20oC over a range of stress levels. Uniaxial creep and constant strain rate tests have been conducted over a range of stress levels, strain rates and temperatures, and triaxial creep tests have been conducted over a range of stress levels and confining pressures on the MIXTURES. The steady-state deformation behaviour of the bitumen is found to be linear at stress levels less than 100 kPa and non-linear power law creep with a power exponent of 2.6 at stress levels higher than 500 kPa. The steady-state deformation behaviour of both MIXTURES is found to be well captured by the Modified Cross Model which predicts linear viscous behaviour at low stress levels and non-linear viscous behaviour at high stress levels. The steady-state deformation behaviour of the DBM mixture is found to be more sensitive to the stress level.The temperature dependency of the steady-state deformation behaviour is found to be well captured by the Williams-Landel-Ferry (WLF) equation. It is found that confinement has a stiffening effect on the steady-state deformation behaviour of the MIXTURES. The stiffening effect of the confining stress is found to be higher for the DBM mixture.

Prediction of the fatigue life of ASPHALTIC concrete is required for design and management of pavements.The prediction of the fatigue life of ASPHALTIC concrete using Artificial Neural Network has been investigated in this research. Sufficient experimental data containing fatigue test conducted on ASPHALTIC concrete over a wide range of conditions was needed for modeling. Therefore, reviewing the literature, the results of the fatigue tests on Kansas State asphalt MIXTURES were found to be appropriate for this research. The parameters of asphalt viscosity, strain level, stiffness of mixture, asphalt content, air voids content and gradation were selected as input variables, while the fatigue life was set as the only output variable. Progressive multilayer perceptron Artificial Neural Network modeling has been used for prediction of the fatigue life, with back propagation training algorithm and numerical optimization technique of Levenberg-Marquardt. Modeling was performed using the neural network tool box and programming in MATLAB, and the results have been compared. It is shown that the programming, can better predict the fatigue life than directly utilizing the tool box. It is also found that Artificial Neural Network can predict the fatigue life of the ASPHALTIC concrete than the regression equation.

In general, mode I loading (pure tension) on the road surface occurs when the crack is placed between the front and rear wheels of the pavement. The results of this research indicate that the amount of fracture toughness depends on factors such as the test temperature, the thickness of the piece, the percentage of free space, and also the parameters of the geometry of the piece. Most of the researches conducted on one or two loading modes are based on the environmental characteristics of asphalt MIXTURES, and the geometrical conditions of asphalt mixture samples, including their cut thickness and the effect of different percentages of filler on the samples, have not been paid attention to. Therefore, in this research, the issue of how the geometrical characteristics of the part can affect the failure toughness of the bending half-disk samples under Mode I loading has been investigated. According to the obtained results, it was observed that as the cutting thickness of the piece increases, more force is required to break the sample.

In most mix design methods, hot mixture asphalt (HMA) is considered to be a single object and only its macroscopic parameters are determined. This is because the microstructure of HMA is very complicated. Asphalt mixture is heterogeneous in nature,therefore, macroscopic parameters alone cannot describe the mechanical behavior of the mixture. In this paper, the analysis and evaluation of microstructure parameters of aggregates in field ASPHALTIC samples are compared to laboratory samples in different compaction energies. Image processing and quantification of the internal structure parameters of the MIXTURES were performed using two-dimensional images from the cut-off of samples and iPAS2 software. The results of the comparison between the parameters of micro and field samples showed that the number of contact points in the cores was close to the number of contact points of Marshall Samples, which were made with moderate compaction energy. It was also determined that by examining MIXTURES of asphalt MIXTURES, new and useful information can be obtained that confirms the necessity of using micro parameters in the mixing design of asphalt MIXTURES.

ASPHALTIC concrete has been used as waterproofing core in embankment dams, since 1948. The large majority of embankment dams' central core is made of clay worldwide. However, as clay is increasingly difficult to find at new construction sites, asphalt concrete was used as a replacement core material. Cores made of clay has also some other disadvantages such as, low shear strength, compressibility, long construction time, requiring higher amount of material and accurate controls during construction, etc. These are in favor of using asphalt concrete, which has advantages such as less sensitivity to weather conditions, less width of core, healing behavior of bitumen, high shear strength etc. In this application, granular materials are used around the ASPHALTIC concrete as filter, which makes a complicated behavior in the interface and needs to be researched by experiments and modeling. This paper describes experimental work and the results of investigating the mechanical behavior of the interface between aggregates and ASPHALTIC concrete. Small scale shear strength test has been used in this study, in which the shear surface is considered as the interface. The effect of bitumen penetration grade, moisture, density and angularity of aggregates on the shear strength parameters at different levels of vertical stresses and a constant shear rate was studied.

Using nano-technology materials in the asphalt pavement industry is new compared with Portland cement concrete. The main objective of this study is to investigate the effects of nano-silica modification on some properties of a penetration grade asphalt cement and a typical asphalt concrete. 60.70 penetration grade bitumen was modified with different percentages of nano-silica (i.e. 1, 3 and 5%, by weight) and was used for making the asphalt concrete specimens. After evaluating the basic properties of the modified binder, the asphalt concrete specimens were evaluated based on the stiffness and resistance against fatigue cracking, moisture damage and permanent deformation. The fatigue life of the modified MIXTURES was also calculated using an already developed regression model. The results showed that penetration grade and ductility increase and softening point decreases with increasing nano-silica content. Furthermore, results showed that the addition of nano-silica results in the increase of stiffness, tensile strength, resilient modulus, fatigue life and resistance against permanent deformation and moisture damage. The reduction of indirect tensile strength in wet the condition decreases with increasing nano-silica content. Dynamic creep test results showed that, the flow number of the control mixture and the mixture containing 1% of nano-silica is much lower than 10000 loading cycles. However, the MIXTURES containing 3 and 5% of nano-silica do not reach to the tertiary creep region after 10000 loading cycles.

In this research, rutting and top-down cracking of ASPHALTIC layer in composite pavement with RCC have been investigated. To this end, 3D models of pavement have been made in Finite Element software of ABAQUS. Performance of 5 different ASPHALTIC MIXTURES has been evaluated and compared. In addition, the effects of using different geogrids in different depths of ASPHALTIC layer on the rutting and top-down cracking have been investigated. The effects of asphalt surface and RCC base thickness on the rutting and top-down cracking has been studied. Results show that type of mixture in surface layer is significantly important in rutting and top-down fatigue cracking. In addition it has been found that placing the geogrid at the mid-depth of asphalt surface decreases the rut depth, and, pacing that at the bottom of ASPHALTIC layer is not effective on the rut depth. The effectiveness of geogrid is found to be dependent on the stiffness of geogrid, type of mixture and thickness of ASPHALTIC layer. Also, placing the geogrid in the mid-depth of ASPHALTIC layer decreases the top-down fatigue life, and placing that at the bottom of ASPHALTIC layer is not effective on the fatigue life. The results of analysis show that rut depth increases with increasing the thickness of ASPHALTIC layer, but is independent of the thickness of RCC layer thickness. The maximum tensile strain at the surface of ASPHALTIC layer is found to vary with the thickness of ASPHALTIC surface and RCC layer. However, the variation does not follow a trend.

The performance of ASPHALTIC pavements during their service life is highly dependent on the mechanical properties of the ASPHALTIC layers. Therefore, in order to extend their service life, scientists and engineers are constantly trying to improve the mechanical properties of the ASPHALTIC MIXTURES. One common method of improving the performance of ASPHALTIC MIXTURES is using different types of additives. This research investigated the effects of reinforcement by randomly distributed glass fibers and the simultaneous addition of nanoclayon some engineering properties of asphalt concrete have been investigated. The properties of a typical asphalt concrete reinforced by different percentages of glass fibers were compared with those containing both the fibers and nanoclay. Engineering properties, including Marshall stability, flow, Marshall quotient, volumetric properties and indirect tensile strength were studied. Glass fibers were used in different percentages of 0.2, 0.4 and 0.6% (by weight of total mixture), and nanoclay was used in 2, 4 and 6% (by the weight of bitumen). It was found that the addition of fibers proved to be more effective than the nanoclay in increasing the indirect tensile strength. However, nanoclay improved the resistance of the mixture against permanent deformation better than the glass fibers. The results also showed that the mixture reinforced by 0.2% of glass fiber and containing 6% nanoclay possessed the highest Marshall quotient, and the mixture containing 0.6% glass fibers and 2% nanoclay possessedthe highest indirect tensile strength.