United States Department of Transportation
i
Three year evaluation of I-40 crack and seat experimental project
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1989-10-01
[PDF-1.22 MB]
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Alternative Title:3 year evaluation of I-40 crack and seat experimental project
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TRIS Online Accession Number:493598
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Edition:Interim report
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NTL Classification:NTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and Performance;NTL-HIGHWAY/ROAD TRANSPORTATION-Construction and Maintenance;
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Abstract:In 1986, Project I-40-3(31) was rehabilitated using crack and seat techniques and overlaying with a 4-inch HMAC overlay. The crack and seat technique was utilized to prevent reflection cracking in the HMAC overlay caused by joints in the existing JPCP. The 4-inch overlay was provided to improve the ride quality and to increase the structural capacity of the pavement section. The project was designated as experimental due to ADOT's limited experience with crack and seat techniques. To evaluate the effect of crack spacing on overlay performance, three crack patterns were tested; 2 ft by 2 ft, 3 ft by 3 ft, and 4 ft by 6 ft. The majority of the 6.5 mile project was constructed using the 3 ft by 3 ft spacing. Only two test sections, one tenth of a mile long each, were constructed using the other spacings. Visual crack surveys and FWD testing were performed at three locations over a period of three years. Roughness, skid, and cracking were obtained as part of ADOT's annual PMS inventory. The results from the FWD testing were used to backcalculate the layer moduli. Large variations in the effective modulus of the cracked and seated JPCP were obtained using the backcalculation technique. The average moduli typically ranged between 3.3 and 7 million p.s.i. The effective moduli tended to fluctuate over time, but no definite trends were established. Structural layer coefficients determined by AASHTO and NAPA procedures indicated no decrease with time, except for the modified NAPA computed 4 ft by 6 ft coefficient which indicated a slight decrease with time. The crack and seat technique and HMAC overlay strategy were successful in reducing roughness on this section of interstate. The eastbound roughness was reduced 254 inches/mile while the westbound roughness was reduced 165 inches/mile. These strategies were not successful in mitigating reflection cracking. Approximately 55% of the joints/cracking have reflected through. /Abstract from report summary page/
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