Comprehensive evaluation of the long-term performance of rubberized pavement, phase II : the influence of rubber and asphalt interaction on mixture durability.
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2014-12-01
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Abstract:This project investigated the long-term performance of hot asphalt mixes containing crumb rubber
modifiers (CRM) added in dry or wet processes. A total of eight asphalt mixtures—four Porous
European Mixtures (PEMs) and four Stone Matrix Asphalts (SMAs)—were designed with PG 76-22
modified with CRM, which was added in either a dry or wet process. These mixtures were compared to
control mixtures using an SBS-modified PG 76-22. Mixtures incorporating a “hybrid”-modified PG
76-22 were also evaluated. First, the samples were weathered in the Georgia Weathering Asphalt Device
(GWAD) for 1,000 hrs and 3,000 hrs and tested to determine their dynamic modulus, fatigue life,
rutting, and Cantabro. Binders extracted from the weathered samples were then evaluated using a
dynamic shear rheometer (DSR), gel-permeable chromatography (GPC), and Fourier transform infrared
spectroscopy (FTIR). Second, the interactions of dry- and wet-processed CRM with asphalt binder were
compared during storage and paving. Results indicated: 1) adding TOR to the CRM binder improved
PG grade and separation resistance; 2) the dynamic modulus, |E*|, of both rubberized PEM and SMA in
dry process did not differ significantly from that of the control mixtures or mixtures using the “hybrid”-
modified binders before and after weathering; 3) the fatigue life (Nf) of unaged rubberized PEM and
SMA in the dry process was similar to that in wet process, although lower than that of control SBS; 4)
after 3000-hrs aging, the fatigue life of the dry-processed rubberized SMA is similar to that of the
wet-processed but lower than that of hybrid and SBS SMA, regardless of strain and stress levels or test
temperatures; 5) the rutting and Cantabro loss of the rubberized PEM and SMA in dry process were
higher than those of control SBS after weathering; 6) CRM and asphalt binder interact during the
production and paving stages based on DSR, GPC, FTIR, and AFM results. The effect of weathering on
the properties of the asphalt binders in rubberized, dry-processed PEMs and SMAs was similar to that in
the wet-processed mixtures but greater than that in the control SBS.
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