|FHWA > Engineering > Pavements > Concrete > Special Project 205|
SP-204 Retrofit Load Transfer
Sharing the Load
The objective of this project is to encourage the concrete paving industry to develop equipment to economically construct slots for retrofit load transfer with smooth, round dowel bars. The development of this equipment would make load transfer across faulted joints or working cracks a cost-effective maintenance and rehabilitation technique for many miles of existing jointed concrete pavement. This technique will extend the service life by providing positive load transfer for undoweled or transversely cracked jointed plain concrete pavement (JPCP) or for working cracks in under-reinforced jointed concrete pavement (JRCP). Various load transfer restoration techniques were constructed and evaluated under an FHWA research contract with the Georgia Department of Transportation in the early 1980's. The use of smooth, round dowels was found to be the most cost-effective way to restore load transfer (FHWA-RD-82-154). Another report, FHWA-RD-88-071, evaluated the performance of experimental sections in eight states and confirmed the excellent performance of load transfer restoration with dowel bars. This technique has been used routinely in Puerto Rico since 1980, but the three slots per wheel path were sewn individually with a hand operated diamond saw. Due to the low labor costs, hundreds of lane kilometers of pavements have been restored for a bid price of $20 per dowel bar installed. However, due to the high cost of short experimental sections, $60 to $100 per dowel in place, States would not let a major contract using this rehabilitation technique. Consequently equipment manufacturers were not willing to make the investment to develop high production equipment to make this a cost-effective technique. SP-204 was developed to break the deadlock.
Diamond sawing equipment is now available from Concrete Textures, Inc., Magnum Diamond & Machinery, Inc. And Cushion Cut. In addition, specially constructed milling heads are available from Keystone Engineering & Manufacturing Corporation.
Diamond sawing equipment has been used on regular construction or maintenance projects in Washington State, Kansas, North and South Dakota. The carbide milling equipment has been used on regular construction projects in New Jersey, West Virginia, and Minnesota. Bid prices have ranged from a low of $22.50 per dowel in place to $50 or more depending on the quantity of dowels installed and traffic control requirements. These projects demonstrate that equipment is now available to economically retrofit load transfer in existing jointed concrete pavements.
Highway agencies are encouraged to consider load transfer restoration as a cost-effective maintenance or rehabilitation technique to extend the service life of concrete pavements in good to fair condition. Available evidence suggests extension of service lives of jointed concrete pavements of 10-20 years are likely depending on the condition of the existing pavement and the estimated number of heavy trucks using the pavement. It is important that this technique be applied before significant distress is present. This will increase the reliability of the technique and make this technique more cost-effective by reducing other concurrent repairs such as full depth slab replacements, undersealing, etc. which may be needed if the necessary work is delayed too long. "If it ain't broke, don't fix it!" does not apply to cost effective maintenance and rehabilitation of portland cement concrete pavements.
Guidelines for load transfer restoration have now been included in the AASHTO/FHWA/Industry Joint Training Course, Construction of Portland Cement Concrete Pavements. This is National Highway Institute Course No. 131033A. The technique has also been included in the Participant's Handbook (dated February 1996) for the one day Workshop on Pavement Maintenance Effectiveness -Preventive Maintenance Treatments. Detailed design and construction guidelines (including generic construction specifications) are included in the SP-204 Final Report (FHWA-SA-98-047) currently available. Additionally, a videotape (Fit to be Tied) showing the various processes used by the Washington State, Kansas, and Indiana Departments of Transportation is available as are copies of Concrete Pavement Rehabilitation Guide for Load Transfer Restoration, FHWA-SA-97-103 (ACPA JPOOIP), 20 pages, and a tri-fold brochure on Load Transfer Restoration.