Part 4: Crack Sealants and LTPP Results: Modification of Bending Beam Rheometer Specimen for Low-Temperature Evaluation of Bituminous Crack Sealants

It is difficult to evaluate effectively the low-temperature stiffness of bituminous hot-poured crack sealants with existing test methods. The standard bending beam rheometer (BBR) was found to be inappropriate for testing soft bituminous-based hot-poured crack sealant, even at a temperature of -40\ub0C. To address this issue, the moment of inertia of the tested beam was increased by doubling its thickness (from 6.35 mm to 12.7 mm). For the new beam dimensions, only 4% of the beam center deflection is due to shear, a value deemed acceptable for sealant evaluation and comparison. On this basis, the BBR stiffness of hot-poured sealants was obtained at several discrete temperatures between -10\ub0C and -40\ub0C to assess the repeatability of the method for the evaluation of the low-temperature stiffness of bituminous sealants. Ten different sealants were tested at -40\ub0C; three of these 10 were further tested at -35\ub0C, -30\ub0C, -28\ub0C, -25\ub0C, and -20\ub0C; and the three "hard" sealants were tested at -10\ub0C. A minimum of three replicates were used. The coefficient of variation on the measured stiffness after 60 s of loading was always lower than 18%, with almost 75% of the measurements having a coefficient of variation less than 10%. A pairwise comparison showed that the modified BBR could be used to classify sealant products according to their measured stiffness. As to the effect of temperature, it was found that the stiffness varies exponentially with temperature in the range of -40\ub0C to -20\ub0C. A statistical analysis of the results indicated that the modified BBR method could be used to classify sealants based on low-temperature stiffness.Il est difficile d'\ue9valuer efficacement la rigidit\ue9 \ue0 basse temp\ue9rature des scellants \ue0 fissures bitumineux coul\ue9s \ue0 chaud en employant les m\ue9thodes d'essai existantes. En effet, on a d\ue9couvert que le rh\ue9om\ue8tre de flexion (RF) standard \ue9tait inad\ue9quat pour la mise \ue0 l'essai de ces produits, m\ueame \ue0 une temp\ue9rature de -40 \ub0C. Au bout de seulement quelques secondes de chargement, la flexion mesur\ue9e d\ue9passait la limite du RF. Pour r\ue9soudre ce probl\ue8me, on a augment\ue9 le moment d'inertie de la poutre test\ue9e en doublant son \ue9paisseur (de 6,35 mm \ue0 12,7 mm), ce qui permet de tester le mat\ue9riau le plus mall\ue9able (\uab mou \ubb) qui soit actuellement disponible sur le march\ue9. Pour les nouvelles dimensions de poutre, on a d\ue9couvert que seulement 4 % de la flexion de la poutre en son milieu est attribuable \ue0 l'effort tranchant, valeur jug\ue9e acceptable aux fins de l'\ue9valuation et de la comparaison des scellants. Partant de ceci, la rigidit\ue9 au RF des scellants a \ue9t\ue9 obtenue \ue0 plusieurs valeurs de temp\ue9rature discr\ue8tes comprises entre -10 \ub0C et -40 \ub0C pour d\ue9terminer la r\ue9p\ue9tabilit\ue9 de la m\ue9thode aux fins de l'\ue9valuation de la rigidit\ue9 \ue0 basse temp\ue9rature des scellants bitumineux. Dix (10) scellants diff\ue9rents ont alors \ue9t\ue9 test\ue9s \ue0 -40 \ub0C; trois (3) de ceux-ci ont \ue9t\ue9 test\ue9s subs\ue9quemment \ue0 -35 \ub0C, \ue0 -30 \ub0C, \ue0 -28 \ub0C, \ue0 -25 \ub0C et \ue0 -20 \ub0C; et les trois (3) scellants \uab durs \ubb ont \ue9t\ue9 test\ue9s \ue0 -10 \ub0C. Un minimum de trois (3) r\ue9p\ue9titions ont \ue9t\ue9 r\ue9alis\ue9es. Le coefficient de variation de la rigidit\ue9 mesur\ue9e apr\ue8s 60 s de chargement \ue9tait constamment inf\ue9rieur \ue0 18 %, pr\ue8s de 75 % des mesures pr\ue9sentant un coefficient de variation de moins de 10 %. Une comparaison par paire a r\ue9v\ue9l\ue9 que le RF modifi\ue9 pourrait ainsi \ueatre utilis\ue9 pour classifier les produits scellants en fonction de leur rigidit\ue9 mesur\ue9e. L'incidence de la temp\ue9rature sur la rigidit\ue9 a \ue9t\ue9 examin\ue9e pour trois (3) scellants. Il s'est av\ue9r\ue9 que la rigidit\ue9 varie de fa\ue7on exponentielle avec la temp\ue9rature dans la plage de -40 \ub0C \ue0 -20 \ub0C. Une analyse statistique des r\ue9sultats a indiqu\ue9 que la m\ue9thode avec RF modifi\ue9 peut servir \ue0 une classification des scellants qui soit fond\ue9e sur la rigidit\ue9 aux basses temp\ue9ratures.Also published in "Transportation Research Board 84th Annual Meeting: Compendium of Papers CD-ROM.(2005)"Aussi publi\ue9 dans "Transportation Research Board 84th Annual Meeting: Compendium of Papers CD-ROM.(2005)"Peer reviewed: YesNRC publication: Ye