Long-term strength of asphalt concrete and its applications

摘要

The objective of the paper is to show that there is an important mechanical characteristic of an asphalt concrete called as a long-term strength which is determined experimentally in an easy way under scheme of direct creep, and using it one can model the deformation and failure of the asphalt concrete at various types of loading. For this purpose the long-term strength is investigated experimentally for a hot fine-grained asphalt concrete at uniaxial tension under stress from 0.0081 MPa to 3.0 MPa within the range of temperatures from +60 degrees C to -24 degrees C. The experiments have been performed in a specifically invented and assembled device which allows determining the mechanical characteristics of materials at tension at various temperatures and types of loading. It is found out that without exclusion for all considered temperatures long-term strength of the asphalt concrete is described by power function with a high accuracy. Exponent characterizing a rate of variation for failure time at variation of stress is increased with the temperature increase: failure time is decreased for 3-7 orders (depending on temperature) at the stress increase for one order. Long-term strength of the asphalt concrete can be also described on the basis of the thermal fluctuation theory. It is found out that activation energy of failure does not depend on stress and temperature, and it is equal to 162.8 kJ/mol; the pre-exponential constant characterizing average time between neighbouring thermal fluctuations depends on stress as well as on temperature; meanwhile the more the temperature the less the effect of stress. Potentials for use are also shown for long-term strength of the asphalt concrete for modeling of the processes of its deformation and failure at loading with a constant rate and in conditions of the thermal stress restrained specimen test. (C) 2020 Elsevier Ltd. All rights reserved.