Structural design of pavements incorporating foamed bitumen mixtures

Gordon Airey,Kranthi Kuna,Nick Thom

doi:10.1680/jcoma.16.00039

Abstract

This paper presents a rational structural design methodology termed the ‘cumulative damage approach’ for road, port and airport pavements incorporating cold bituminous mixtures with foamed bitumen. This has been developed along with a laboratory test, the uniaxial indirect tensile test, to evaluate the fatigue characteristics of these mixtures. The test was developed with a view to addressing the limitations of conventional fatigue tests for foamed bitumen mixtures. The new design approach takes account of the actual stiffness evolution of the mixtures obtained from the fatigue test. It is compared with a traditional approach for conventional flexible pavements, which is based on pavement life as a function of computed tensile strain in the material and interpretation of fatigue data in a conventional way. The results show that the traditional design approach yields conservative outcomes for pavements with foamed bitumen mixtures if the same transfer function or shift factor used for hot mix asphalt is applied. The results also show that if all factors other than induced load influence are the same, the shift factor for foamed bitumen mixtures could be 25–35% higher than for hot mix asphalt.

Highlights

The structural design of road, port and airport pavements is required to make sure that the structure performs structurally and functionally in an economically viable manner for the designed life period
This study has introduced a laboratory fatigue test, the ‘uniaxial indirect tension test’ for foamed bituminous mixtures and a rational structural design approach, the ‘cumulative damage approach’, for pavements incorporating foamed bituminous mixtures
The uniaxial indirect tensile test is believed to address some of the limitations of the traditional fatigue tests of foamed bituminous mixtures

Summary

Introduction

The structural design of road, port and airport pavements is required to make sure that the structure performs structurally and functionally in an economically viable manner for the designed life period. The mechanistic–empirical method, which is based on the mechanics of the materials and relates an input such as wheel load to an output (pavement layer response) such as stress or strain, is a possible option This paper applies this mechanistic–empirical approach to the design of pavements incorporating cold bituminous mixtures with foamed bitumen (foamed bitumen mixtures). Offprint provided courtesy of www.icevirtuallibrary.com Author copy for personal use, not for distribution excessive aggregate loss during saw cutting, the variability of test results has been found to be very high using beam fatigue tests (Long et al, 2002; Ramanujam and Jones, 2007) In view of these limitations of the applicability of indirect tensile fatigue tests and beam fatigue tests to foamed bituminous mixtures, in this study the applicability of the uniaxial compression test was studied. Test specimens can be prepared from a core taken from an in-service pavement for validating the in-service condition of a pavement layer

Materials and methods

Uniaxial indirect tensile fatigue test

Findings

Conclusions