Imad L. Al-Qadi, 1 Eli. H. Fini, 2 Mostafa A. Elseifi, 3 J-F. Masson, 4 and Kevin M. McGhee 5 Development of a Viscosity Specification for Hot- Poured Bituminous Sealants * ABSTRACT: Current crack sealant specifications focus on using simple empirical tests such as penetration, resilience, flow, and bonding to cement concrete briquettes ASTM D 66901 to measure the ability of the material to resist cohesive and adhesive failures. There is, however, no indication of the pertinence of these standard tests to predict the success of field installation and sealant performance. In an effort to bridge the gap between sealant fundamental properties and field performance, performance-based guidelines for the selection of hot-poured crack sealants are currently being developed. This paper proposes a new viscosity test procedure to help assess the propensity of sealants to wet the crack surface during installation. The proposed procedure calls for the use of a Brookfield rotational viscometer equipped with a modified spindle rod and an SC4-27 spindle at a speed of 60 r/min. Sealants are heated 20 min at the recommended installation temperature and the viscosity is measured after 30 s of spindle rotation in the hot sealant. These experimental conditions provide viscosities representative of sealant viscosity at shear rates during field application. The repeatability for within laboratory and between laboratories was found to be 5.4 and 17 %, respectively. This repeatability is comparable with the corresponding variability of the SuperPave viscosity test for asphalt binders. KEYWORDS: viscosity, crack sealant, shear rate, non-Newtonian fluid Introduction The performance of a pavement depends on the effectiveness and timeliness of maintenance efforts. Deferred maintenance increases the severity of distress and leads to a more rapid decline of pave- ment condition. An effective maintenance program helps to main- tain riding quality, delays deterioration, and corrects pavement de- ficiencies. It has been reported that a dollar spent during the early stage of pavement deterioration saves as much as four to five dol- lars in the subsequent stages of deterioration 2. Pavement maintenance includes preventive and corrective ac- tivities. Preventive maintenance protects a pavement against a spe- cific distress and thus decreases the rate of deterioration. In con- trast, corrective maintenance activities are performed to address specific pavement failure or area of distress. For effective preven- tive maintenance, regular treatment of pavements is needed. More- over, regularly treating pavements offers agencies cost savings over repairing pavements that have been allowed to deteriorate. Crack sealing is a preventive maintenance activity that is widely recognized to be cost-effective if the product is properly selected and installed 3. This maintenance activity reduces water infiltra- tion into the pavements and therefore delays pavement deteriora- tion caused by the weakening of subgrade and aggregate layers, loss of subgrade support, and stripping of hot-mix asphalt HMA layers. For a material to provide acceptable performance as a hot- poured bituminous crack sealant, it must resist adhesion and cohe- sion failures as well as degradation in the range of service tempera- ture at which it is expected to be used. Since the 1950s, crack sealant specifications have been based on physical property tests that are easy to perform 4. The specifica- tions, ASTM D 5329 5 and AASHTO M173 6, focus on utiliz- ing simple empirical tests such as cone penetration and softening point to measure the ability of sealants to resist cohesive and adhe- sive failures. Although the viscoelastic behavior of crack sealants is more complex than that described by these simple empirical tests, these consistency tests have served well over the years for specify- ing crack sealants and to ensure the consistency of sealant proper- ties 7. As a result of increasing traffic, axle loadings, and tire pressures in recent years, as well as premature failure of hot-poured crack sealants, a new range of highly-modified crack sealants have been available that can have quite complex behavior compared to tradi- tional sealant materials. These new sealants have a relatively lower strength than conventional sealants but are extremely flexible under loadings allowing them to stretch considerably without enduring failure 8. The new crack sealants are highly-modified asphalt binders with polymer content as high as 18 %, recycled rubber con- tent as high as 50 %, and oils with a concentration between 3 and 13 % 9. Assessment of the current specifications on these new classes of crack sealants revealed that these consistency tests do not ad- equately describe the linear viscoelastic properties that are needed to relate physical properties to performance, to relate sealant chem- istry to performance, and to develop a performance-related crack sealant specification system. While some sealants provided accept- Manuscript received January 14, 2006; accepted for publication January 17, 2007; published online March 2007. 1 Founder Professor of Engineering and Director of Illinois Center for Trans- portation and Graduate Research Assistant, Advanced Transportation Research and Engineering Laboratory, Department of Civil and Environmental Engineer- ing, University of Illinois at Urbana-Champaign, Urbana, IL 61801. 2 Graduate Research Student, Department of Civil and Environmental Engi- neering, University of Illinois at Urbana-Champaign, Urbana, IL 61801. 3 Assistant Professor, Department of Civil Engineering and Construction, Bradley University, Peoria, IL 61625. 4 Senior Research Officer, Institute for Research in Construction, National Research Council of Canada, Ottawa, K1A 0R6, Canada. 5 Senior Research Scientist, Virginia Transportation Research Council, VDOT, Charlottesville,VA 22903. *The contents of this paper reflect the view of the authors who are respon- sible for the facts and the accuracy of the data presented herein. The content does not necessarily reflect the official views or policies of the Departments of Transportation participating in the pooled fund study or the Federal Highway Administration. This paper does not constitute a standard, specification, or regu- lation. Journal of Testing and Evaluation, Vol. 35, No. 4 Paper ID JTE100260 Available online at: www.astm.org Copyright © 2007 by ASTM International, 100 Barr Harbor Drive, PO Box C700,West Conshohocken, PA 19428-2959. 1 Copyright by ASTM Int'l (all rights reserved); Mon Aug 5 15:22:45 EDT 2013 Downloaded/printed by Center For Library Initiatives pursuant to License Agreement. No further reproductions authorized.