Improved Life for Longitudinal Joints in Asphalt Pavement - WisDOT ...

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WisDOT ApproachThe current WisDOT design of longitudinal joints in asphalt pavement is a “Michigan joint” or “wedge joint”design. It features a ½-inch notch at the top of the joint, a vertical drop perpendicular to the lane surface, and a 12:1tapered slope into the space where the next lane will be laid. This joint is treated with a tack coat and the next layeris rolled over the joint slope. If the joint is cold, it is heated and tacked and the next lane is placed. See WisDOTStandard Specifications, Sections 450.3.2.5(6) and 450.3.2.8, athttp://roadwaystandards.dot.wi.gov/standards/stndspec/sect450.pdf (pages 5 to 6 of the PDF). For a drawing, see theWisDOT Facilities Development Manual, Chapter 14, Procedure 14-10-5, Figure 5, athttp://roadwaystandards.dot.wi.gov/standards/fdm/14/FDM14.pdf (page 29 of the PDF).Joint DesignThe Michigan or tapered joint became the standard in the 1990s. A variety of publications have spun off NCATReport No. 97-4, published in 1997, which formally established the effectiveness of the tapered or notched joint.National Center for Asphalt Technology. Since at least the late 1990s, the Michigan or tapered joint design hasbeen considered the best option for longitudinal joints in asphalt pavements and asphalt overlays. An NCAT studycompared joints in Michigan, Wisconsin, Colorado and Pennsylvania, and the results led to a number of later articlesand studies. These include:• Longitudinal Joint Construction Techniques for Asphalt Pavements, Prithvi Kandhal and Rajib Mallick,NCAT Report No. 97-4, August 1997.http://ntl.bts.gov/lib/7000/7900/7944/rep97-4.pdfThis project studied 30 designs in four states. The best-performing joint after four years was a Michiganjoint that featured a 12.5-mm vertical offset and a 12:1 taper.• A 2007 NCAT PowerPoint presentation includes material from the 1997 study (seehttp://www.ucs.iastate.edu/mnet/_repository/2007/asphalt/pdf/practices%20and%20specifications%20for%20longitudinal%20joints%20-%20prowell.pdf). The presentation discusses measuring performance at thetime of construction, describes German methods, and presents four states’ specifications. Best-performingmethods for construction include:o Use of rubberized joint adhesiveo Notched-wedge design, with a 12:1 taper over 12 inches, and a notch of 0.5 to 0.75 incheso Use of cutting wheel and edge-restraining deviceo Rolling from hot side with 6-inch overlap• A PowerPoint presentation on the NCAT data confirms the Michigan joint’s effectiveness, and notesseveral factors in effective joint construction (seehttp://www.asphaltalliance.com/upload/Longitudinal%20Joints%20-%20Ray%20Brown.pdf). Conclusionsinclude:o Vertical offsets are essential.o Rubberized joint adhesive is effective.o Rolling should be conducted as soon as possible.o The joint can be compacted to a density within 2 percent of the mat density.• See also “Study of Longitudinal-Joint Construction Techniques in Hot-Mix Asphalt Pavements,” PrithviKandhal and Rajib Mallick, Transportation Research Record No. 1543, 1996: 106-112. (See attached file.)• The “New Jersey” joint, one of the other designs tried and found less effective, is a 3:1 wedge without anotch at the unconfined edge of the first lane that is heated before the next lane is placed.• “Asphalt Answers,” Roads and Bridges Magazine, January 1998.http://www.roadsbridges.com/ASPHALT-ANSWERS-article973Kandhal writes that after five years, the Michigan joint remains the most promising design.TRB“Evaluation of Notched-Wedge Longitudinal Joint Construction,” M. Shane Buchanan, Transportation ResearchRecord No. 1712, 2000: 50-57. (See attached file.)This paper, from the 2000 TRB Annual Meeting, follows up on notched-wedge joints in Alabama, Colorado,Indiana, Maryland and Wisconsin, and finds from cores that they’ve been performing well in terms of density at thelongitudinal joint.2
Compaction and DensityProper density and compaction at the longitudinal joint present difficulties to construction crews. For the first pavedlane, roller passes push material out, resulting in reduced density at the edge. In paving a second lane, with aconfined edge at the first, proper compaction at the joint can be hampered by cooling of the HMA. Many of thereports below focus on the effectiveness of a density or permeability specification—in some cases with incentives ordisincentives to force contractor compliance. The following research and documents focus on density andcompaction of longitudinal joints in terms of construction, specifications, quality and performance.NCHRP. Project 9-15, “Quality Characteristics and Test Methods for Use in Performance-Related Specifications ofHot Mix Asphalt Pavements,” completed June 2004.http://www.trb.org/trbnet/projectdisplay.asp?projectid=951Phase I identified construction-based performance characteristics of HMA pavements that warrant testing for qualityassurance, and distilled these to five characteristics for testing; longitudinal joint density was one of these. Phase IItested these qualities with available methods to determine best methods and quality standards.For a detailed summary of findings, see Research Results Digest 291, August 2004, athttp://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rrd_291.pdf. The digest addresses longitudinal joint density onpages 5-6. Research compared density readings from a pavement quality indicator, a nuclear gauge, and frompavement cores, finding PQI results the most accurate. Based on PQI readings, investigators categorized jointdensity relative to lane or mat density in three classifications as a guideline for specifications:• Good density at the joint measures greater than 97 percent of mat density.• Fair density at the joint measures 93 to 97 percent.• Poor density at the joint measures less than 93 percent.KentuckyCompaction at the Longitudinal Construction Joint in Asphalt Pavements, L. John Fleckenstein, David Allen andDavid Schultz Jr., March 2002.http://www.ktc.uky.edu/Reports/KTC_02_10_SPR200_00_1F.pdfInvestigators tracked joint construction at 12 pavement sites during construction, evaluating the density achieved onthe longitudinal joints. Four construction approaches were used, including building notched-wedge (12:1) joints aswell as using a restrained edge, a joint re-heater and a Joint Maker. All joints were performing well afterconstruction. Those that employed joint adhesives were performing as well as or better than those that did not,leading investigators to recommend the use of joint adhesives.TRBFactors Affecting Compaction of Asphalt Pavements, Transportation Research Circular E-C105, September 2006.http://onlinepubs.trb.org/onlinepubs/circulars/ec105.pdfThis e-circular includes four articles on longitudinal joint construction, beginning on page 85 of the PDF. Topicsinclude compaction, voids, measuring density at joints, and durable joint construction. Important factors in buildingdurable joints include:• Proper compaction of the unsupported edge of the first lane placed.• Ensuring that overlap of asphalt from the second lane placed is about 1 to 1.5 inches to ensure enoughmixture in the new lane for a properly compacted lift and to prevent a depression between lanes. Overlapon the first lane must be shoveled off the pavement, not raked into the new lane.• Placing the mixture precisely enough to avoid raking at the joint.• Compacting the joint from the warm pavement lane, not the cold, and allowing the roller to extend no morethan 6 inches over the cold lane.Construction and SpecificationsThe following activities focus on construction techniques and activities, as well as on the development andeffectiveness of a density specification for longitudinal joints.KansasLongitudinal Joint Construction for Hot Mix Asphalt Pavements, M.V. Akpinar and M. Hossain, March 2004.http://www.ksdot.org/idmws/DocContent.dll?Library=PublicDocs^dt00mx38&ID=003686991&Page=1This literature search explores density problems at the longitudinal joint, including construction techniques andspecifications from various studies.3
Page 4 and 5: Maine“Longitudinal Joint Study,
Page 6 and 7: Quality ControlThe following resear

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