|M.Sc Student||Noam Weinstein|
|Subject||Comparison of the Mechanical Properties of Dense and|
|Department||Department of Civil and Environmental Engineering||Supervisors||Dr. Sidess Arieh|
|Professor Emeritus Uzan Jacob|
|Full Thesis text - in Hebrew|
Asphalt pavement systems experience structural and functional distress modes such as fatigue cracking, rutting, roughness etc. These distresses are closely related to the physical properties of the asphalt layers. Traditionally, the asphalt mixes used by the Israeli Public Works Department (IPWD), currently, the Israeli National Roads Company, were dense graded (characterized by a relatively smooth surface texture). By the end of the 90’s the IPWD introduced new ‘structural mixtures’ identified as ‘S’ mixtures. These mixes had an ‘S’ shaped gradation curve and hence their given name; they were locally developed, inspired by the SUPERPAVE research effort that took place in the USA at the time. In comparison to the traditional dense graded mixes, ‘S’ mixes with the same maximum aggregate size and similar air void content have lower binder content and deeper surface texture.
The overall objective of this study was to compare the mechanical properties of the dense graded asphalt mixes with those of the ‘S’ mixes. The first part of this report presents a literature review that critically examines: (i) The mechanical dissimilarities between the different mixture types considered in this work and the meaning of these laboratory properties to in service (field) pavement performance; (ii) The influence of the volumetric properties of the considered mixes on different distress modes and pavement performance; and (iii) evaluation of the type of laboratory tests and derived parameters that can potentially forecast in situ pavement performance.
In the second part of this report, the specimen preparation method for the different tests is presented.
In the third part, the test results obtained in this study are presented and analyzed mechanistically. Three test types were carried out in this research using a servo-hydraulic Instron loading frame. The first consisted of sinusoidal loading in uniaxial mode to determine the dynamic modulus and phase angle of the different mixes. The second test performed was a uniaxial direct tension test to failure. The third test included cyclic uniaxial compression for attaining the resulting permanent deformation and number of cycles to failure.
In general terms, the laboratory study performed herein indicated that the dense graded mixes are superior to the ‘S’ type mixes. The test results, however, are not sufficient to reach such a conclusion regarding actual field behavior of pavements made of these materials. It is therefore recommended that this study will be expanded to include more advanced triaxial tests followed by sophisticated structural simulation and further validated with the aid of controlled full scale testing.