Mix ratio optimization design method for hot in-place recycled asphalt mixtures

Abstract

The design of components for hot in-place recycling (HIR)

is the key to determining the performance of asphalt pavement

regeneration. However, existing design methods have numerous

problems, such as the large demand for sample size, and the ne

glect of the interaction of different factors and levels. In order to

establish a reasonable component design method for hot in-place

recycled mixtures, this study analyzed the action mode of the re

juvenator and optimized the mix design method using orthogonal

tests. The regeneration mechanism of the rejuvenator in the re

claimed asphalt pavement (RAP) was analyzed and the optimum

working conditions of the rejuvenator were determined initially

by means of physical performance, chemical composition and dy

namic shear rheological tests. In addition, the influences of reju

venator, RAP and new asphalt at high and low temperatures and

the water stability of the recycled asphalt mix were analyzed, with

testing using an orthogonal design method combining rheological

tests for wheel rutting, trabecular bending rheological and freeze

thaw splitting tests, the optimum design of the recycled mixture

was determined on this basis. According to the test results, the

rejuvenator and RAP can influence the pavement performance of

the recycled mixture more than new asphalt. When the rejuvena

tor dose is 5% of the total asphalt mass, the ratio of RAP and new

asphalt is 80% and 0% of the mixture, respectively, the recycling

effect is the best. The proposed method is economical and envi

ronmentally friendly and has been well applied in ordinary trunk

road maintenance engineering in Hanzhong City, Shaanxi Provin

ce, China, since 2017. The research findings can provide references

for HIR engineering.