Development of Rutting Prediction Model for Paving Mixes Using Creep Test.(Dept.C)

Abstract

Rutting phenomena in asphalt pavement is a complicated problem: because of the overlapping of many factors causing it. So, many methods have been proposed to assess rutting resistance of paving mixes. Among those proposed methods, the static creep test represents the most promising one for this purpose in Egypt. The test is typically conducted at 40°C for at least one hour. Hanging up the test for a long period at elevated temperature may be difficult for routine laboratory mix design in Egypt. So, the current study is primarily concerned with simplifying a technique that can be used in mix design phase for predicting the expected rut depth in an asphalt layer at the actual temperature after actual wheel passes. To achieve this objective, many paving mixes typically used in pavement construction, were formed using different aggregate types and gradations, asphalt contents, compaction efforts. Then, the expected rut depths of these mixes were measured using creep test at three test temperatures along with four repetitions of wheel loads. Also routine mix characteristics of these mixes were measured Rutting prediction models for cach definite combination of traffic and temperature were developed using the results of creep tests and routine mix characteristics. Then, a general model was developed. This model can be used to predict the rut depth of an asphalt mix at the actual temperature along with the actual number of wheel passes with the aid of routine mix characteristics. The predicted values of rut depth using the developed model compared very closely with the measured values. Finally the study recommended to use coarse graded mix, crushed sand, low asphalt content and sufficient compaction to increase rutting resistance of paving mixes.