Thesis (M.Eng.) - SEATO Graduate School of Engineering

A thesis submitted in partial fulfillment if the requirements for the degree of Master of Engineering in the SEATO Graduate School of Engineering, Bangkok, Thailand.

In recent years several rational methods of design have been developed for determining the thickness of flexible pavements. Knowledge of the modulus of rigidity of each layer of the pavement is prerequisite for using these methods. The methods in common use for evaluating the modulus in the laboratory necessitate the use of costly vibration machines. It was desired to find a simple, reasonably precise, method which would enable one to obtain the modulus as rapidly as possible. For this purpose the Marshall test has been adopted. The present research is mainly based upon a study by Michelin in 1964 for determining the modulus of rigidity of bituminous paving mixtures. One objective of this investigation was to check the accuracy and validity of Michelin{u2019}s conclusions by extending his work using different grades of asphalt in the mix. Two asphalt cements and three different blends of aggregate were utilised in the tests. The research was extended to find the effect of the viscosity of the asphalt cement on the physical properties of the mixture (temperature susceptibility and modulus of rigidity). For this purpose, tests were conducted on specimens comprising the same blend of aggregate mixed with two grades of asphalt cement.