PERMANENT DEFORMATED IN ASPHALT PAVEMENTS CAN BE PREDICTED

Abstract

The experiments conducted, the results obtained, and the field verification is described of a method (based on simulating the field situation in the laboratory) for predicting rut depths in asphalt concrete pavements. The apparatus and test procedures included a high pressure triaxial chamber with temperature control, electro-hydraulic systems for the independent control of vertical and horizontal stresses, and a variety of ancillary equipment. The equipment was capable of applying repeated axial and laterial stress pulses of any desired shape, in phase with one another, with pulse times ranging from 0.01 to 1.0 sec. The equipment which could apply the axial stress as either tension or compression, could also incorporate rest periods between pulses ranging from 0 to several seconds. Temperature conditiosn could be controlled within a tolerance of plus or minus 0.5 F. It is concluded from the study that the mechanism of rutting in asphalt concrete sections subject to moderate tensile stresses is almost entirely due to lateral distortion of the tension zone. An equation is presented which describes the permanent deformation characteristics of asphalt concrete mixtures. Uses for future research are indicated.