Memorandum
City of Lawrence
Public Works
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TO: |
Mike Wildgen |
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FROM: |
Chuck Soules |
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CC: |
Dave Corliss, Debbie Van Saun |
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Date: |
January 27, 2005 |
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RE: |
Crack Sealing |
Why Crack Seal? Simply put, sealing pavement cracks prevents water from entering the base and subbase which will extend pavement life. Asphalt and concrete pavements expand and contract with seasonal temperature changes. Consequently, cracks and joints are expanding and contracting as pavements move. Sealing the cracks with a flexible rubberized asphalt that bonds to the crack walls and moves with the pavement will prevent water intrusion. As part of a pavement management system, crack sealing can reduce pavement deterioration by restricting water penetration into underlying base and subbase layers. This restriction helps to maintain pavement structural capacity and limits degradation.
How is Crack Sealing done? Crack Sealing is a routine maintenance activity. Generally, cracks which have opened up more than 1/4 to 1/2 inch are candidates for sealing. Cracks wider than 1/2 inch may require a filler material prior to crack filling. The most common types of cracks which are sealed include longitudinal cracks, transverse cracks, reflective cracks, edge and block cracks. Fatigue or alligator cracks are not typically sealed individually because the intensity of crack patterns usually warrants an area treatment such as removal and replacement, overlay, or seal coat (chip seal/slurry seal).
Typically, sealing procedures involve the following steps:
o Adequate traffic control
o The cracks are cleaned with a hot air lance
o Removal of debris or loose material
o Pour hot crack filling material into the crack
o The surface is finished with a shoe leveler/squeegee
The City of Lawrence crack sealing program uses Dreery Super-strech, a rubberized asphalt cement. The process is time consuming and labor intensive. It is best completed in late fall and early spring when temperatures are cool to moderate as pavements contract and cracks are opening up.
Crack Sealing Program. Crack sealing is only one of the maintenance treatments used by the Public Works Department. Other treatments used in Lawrence include removal and replacement, chip sealing, mill and overlay, white topping, and some micro surfacing.
The City Commission approved $100,000 in the 2005 budget for a contracted crack seal project. Projects are typically bid per pound of material placed. It is estimated that the budgeted amount will complete/place 75,000-80,000 lbs. at a bid of $1.25-$1.30/lb. Maintaining (or increasing) this program in the 2006 budget is recommended. We have already begun our 2005 program (as weather permitted) and have placed 4656 lbs. The following table provides a five-year summary of resources devoted to the Crack Seal Program.
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Crack-sealing 2004* |
Pounds of material: Material costs: Labor costs: Labor hours: |
15,480 $7,367 $18,721 1,230 |
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Crack-sealing 2003 |
Pounds of material: Material costs: Labor costs: Labor hours: |
17,040 $9,372 $21,022 1,630 |
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Crack-sealing 2002 |
Pounds of material: Material costs: Labor costs: Labor hours: |
26,990 $18,330 $25,968 1,982 |
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Crack-sealing 2001 |
Pounds of material: Material costs: Labor costs: Labor hours: |
11,475 $5,723 $14,049 (est) 2,152 (est) |
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Crack-sealing 2000 |
Pounds of material: Material costs: Labor costs: Labor hours: |
11,530 $4,415 $14,050 (est) 2,153 (est) |
*The list of streets completed in 2004 includes:
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Massachusetts from 15th Street to 23rd Street |
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Airport: |
Main taxiway Parallel taxiway Taxiway from terminal to KU hanger |
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North Lawrence: |
Locust Street Maple Street 3rd Street N. 2nd Street North Street Lyons Street Gardens Court, Maine 9th Street, 8th Street, 7th Street Oak, Elm, Ash, and Walnut Streets |
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City |
Pounds of Material Placed |
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Manhattan |
40,000 by City crews |
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Hays |
96,000 contracted |
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Emporia |
8,000 contracted |
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Newton |
53,300 by City crews |
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Ottawa |
9,000 by City crews |
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Hutchinson |
82,000 by City crews |
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Winfield |
21,465 by City crews |
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Topeka |
3,250 by City crews |
Following is a brief survey of the pounds of crack seal material placed by other Kansas communities in 2004.
Please let me know if additional information is required.