RHEOLOGICAL BEHAVIOUR OF SHEET ASPHALT PREMIX

Abstract

Bituminous pavements exhibit a varied kind of response under high speed trunk routes vis-a-vis slow speed congested arterials and parking lanes. In the former case the pavements exhibit linearly or non-linearly elastic stress-strain res. ponse while under creep speed and static traffic conditions, they exhibit viscoelastic response. In order to account for both conditions of trafficking, two set of experiments have been conducted on sheet asphalt premix, viz. creep test under compression to characterise the time dependant stress. strain response and triaxial compression test to establish the linear/non-linear elastic response. To start with, the mix was designed using Hubbard-Field stability criteria. Unconfined compression tests were conducted to establish the compressive strength of the mix. Creep tests were then carried out at 4 different stress levels viz. 12.00, 17.18, 23.00 and 30.70 percent of the unconfiend compressive strength. Similarly, triaxial tests were conducted at four different levels of lateral confin-ement viz. 0.5,1.0,1.4 and 2.0 kg/cm2. For analysis of creep data, various techniques such as generalised strain measure as well as classic visco. elastic models have been reviewed. Finally the test data have been analysed using the generalized strain measure technique. It could be possible to split the total creep response into three phases and develop characterizing coeffi-cients for each phase vii. primary creep secondary creep and tertiary creep. The analysis of triaxial test data indicates that for a given lateral confinement, the elastic modulus value rema-ins linear initially and then tends to be non-linear. Depen» dancy of elastic modulus on lateral stress level is also exibibited by the test. A linear eqUation qould be developed to explain the above influence.