Dependence of the Recycled Asphalt Mixture Physical and Mechanical Properties on the Grade and Amount of Rejuvenating Bitumen

Donatas Čygas,Nemunas Abukauskas,Darjušas Mučinis,Henrikas Sivilevičius

doi:10.3846/bjrbe.2011.17

Donatas Čygas, Nemunas Abukauskas + Show 2 more

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https://doi.org/10.3846/bjrbe.2011.17

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Abstract

Due to destructive factors (traffic loads, climatic and weather conditions, improper exploitation materials), bitumen properties irreversibly change in unserviceable asphalt concrete. Due to irreversible processes of oxidation the aged bitumen stiffens, its physiochemical properties, ductility, adhesion and cohesion as well as sectional composition (relative amounts of asphaltenes, oils and resins) change. Bitumen in the reclaimed asphalt pavement (RAP) may be restored to properties approximate to those of the virgin bitumen by adding the following rejuvenators: softening or rejuvenating agents as well as soft bitumen. The article presents the experimental data on RAP obtained from laboratory tests conducted with Marshall specimens without additives when RAP was supplemented by different types of virgin road bitumen, the paving grade of which was 50/70, 70/100, 100/150, 160/220, respectively. The content of newly added binder of all types to RAP was 0.5%, 1.0%, 1.5%, 2.0%, and 50/70 in addition and 4.0% and 6.0% of RAP mass. The total bitumen content increased by the same percentage amount in the reclaimed asphalt, which was not always optimal. Marshall specimens were formed with these bitumen contents, the tests of which enabled to identify stability (S), flow (F), Marshall quotient (S/F), air voids content (Vm), bulk density (SDD – ρb SD) of asphalt concrete samples and the maximum density of asphalt. Having extracted all RAP and reclaimed asphalt samples according to the differential method, the factual content of soluble binder in them and its penetration, softening point, Fraass breaking point, ductility and penetration index Ip were calculated. The dependences of the reclaimed asphalt physical and mechanical parameters on the virgin rejuvenating bitumen grade and its added percentage amount were obtained. Data analysis and their generalization was conducted.

Highlights

Hot mix asphalt (HMA) is typically a mixture of approx 5% liquid asphalt binder and 95% solid aggregate
The article presents the experimental data on reclaimed asphalt pavement (RAP) obtained from laboratory tests conducted with Marshall specimens without additives when RAP was supplemented by different types of virgin road bitumen, the paving grade of which was 50/70, 70/100, 100/150, 160/220, respectively
The aim of this study is to identify the impact of the grade and the percentage amount of the rejuvenating virgin bitumen on the properties of the

Summary

Introduction

Hot mix asphalt (HMA) (called “asphalt” outside the United States) is typically a mixture of approx 5% liquid asphalt binder (i.e., asphalt cement, called, “bitumen” outside the United States) and 95% solid aggregate (e.g., crushed stone, gravel, sand, or reclaimed asphalt pavement). In HMA, both liquid asphalt binder and aggregate are heated prior to mixing (the name “hot mix”) (Mundt et al 2009). The use of locally available materials reduces the energy required to move large quantities at long distances, and the use of recycled asphalt pavement reduces both the quantity of aggregate and the quantity of asphalt required (Bennert, Dongré 2010). In Lithuania as well as other countries, the material of the used asphalt pavement is hot-recycled in place or in-plant (Karlsson, Isacsson 2006; Mučinis et al 2009; Sivilevičius 2011b). The interest in asphalt recycling increased in 1970s because of the petroleum crisis and the development of a large scale milling machine in 1975 (Carter, Stroup-Gardiner 2007)

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