Poker Chip Testing of Rubberized Asphalt Binders

Description

Poker Chip Testing of Rubberized Asphalt Binders

Bibek Regmi
Graduate Research Assistant, Department of Civil and Environmental
Engineering, The Grainger College of Engineering, University of
Illinois Urbana-Champaign, bibekr2@illinois.edu
Renan Santos Maia
Graduate Research Assistant, Department of Civil and Environmental
Engineering, The Grainger College of Engineering, University of
Illinois Urbana-Champaign, rmaia2@illinois.edu
Ramez Hajj
Assistant Professor, Department of Civil and Environmental
Engineering, The Grainger College of Engineering, University of
Illinois Urbana-Champaign, rhajj@illinois.edu

ABSTRACT. The poker chip test has recently been introduced as a measure of asphalt binder
performance, and has been shown to be sensitive to modification, aging, and inclusion of
recycled asphalt materials. The rationale of the poker chip test is to capture the intermediate
temperature cohesive strength and ductility in a realistic stress state compared to what the
binder experiences in a mix, confinement between two aggregates inducing high hydrostatic
stress. The test utilizes uniaxial tension to examine the failure properties of the binder confined
in a thin film. Although several polymers have been extensively studied using this test, asphalt
rubber systems remain a challenge. Crumb rubber particles are generally large compared to
the film thickness in this test and therefore create size effect issues in poker chip specimens.
However, the introduction of the idea of hybrid crumb rubber blending introduces potential for
examining its poker chip failure properties. This study examines several experimental scenarios
in which poker chip test can be used to capture the properties of rubberized asphalt binders
using both wet method of addition and a form of hybrid blending, in which particles were placed
in the poker chip mold dry but heated for a longer time to allow some dispersion into the binder
matrix. As a further alternative, a smaller size crumb rubber powder which was suitable in
terms of size (less than one third of the film thickness) was also used in the test. In addition to
the poker chip testing, a framework is presented for using fine aggregate matrix to perform
realistic stress state testing using the dynamic shear rheometer, for multi-scale analysis and
linking binder to mix properties when hybrid and wet process rubber modification is used.

KEYWORDS: asphalt binder, poker chip test, crumb rubber, fine aggregate matrix