By determining the displacement (as a function of temperature) and the resulting stretching of each chip seal, it should be possible to estimate their bridging ability. By combining the different binders with the stone and using both un-aged and aged binders, the varying degrees to which the different systems can span cracks of different widths and movements would be demonstrated. The project would help the RIDOT in determining the most effective type and grade of modified asphalt to use in their pavement preservation program.
Highway
Cracking occurs in pavements as a result of aging, thermal stresses and traffic loading, letting water into the crack. The water freezes, widening the cracks and also undermining the pavement subbase. Traditional methods use a chip seal (a liquid binder asphalt membrane sprayed over the pavement with broadcast stone chips rolled into the binder) to prevent the ingress of water into the cracks. Recently, rubberized asphalt chip seals have been used by the RI Department of Transportation (RIDOT) as a significant element in the pavement preservation program started in 1999 (pavement preservation is a maintenance strategy embraced by Congress via the passage of the highway transportation bill, TEA-21; the intent is to enhance the longevity of the pavements and thereby maximize the use of existing funds). However, cold weather can cause the pavement to shrink and, subsequently, the cracks to enlarge. The chip seal over the crack is stretched as its own stiffness is increasing with the drop in temperature. This stress can, over time, fracture the membrane. With the development of new modified binders, it is important to know the mechanics of failure of these new chip seal membrane systems and how well they can bridge cracks and allow for movement of the cracks in cold weather.
This project is terminated because of the death of the PI.
Task 1: Literature Search
.Study current state of the art and practice
.Examine similar test methods
.Determine appropriate binders
.Determine aggregate sources
Task 2: Sample Material Collection
Binder
.virgin binder (AC-20 equivalent)
.rubberized asphalt binder
.polymer modified asphalt
.chemically modified crumb rubber asphalt
.emulsified asphalt
Aging of binder by PAV
Stone (typical chip seal type)
Task 3: Equipment Setup/Modification
Creation of jig for sample fabrication
Modification of environmental chamber
Software Programming for temperature controlled test algorithm
Procure gauges (temperature, LVDT)
Task 4: Preliminary Testing of Aggregate/Binder
Binder
.SHRP protocol
.ductility
.elastic recovery
Aggregate testing -RIDOT protocol
Task 5: Test Specimen Preparation for 0 and .025 inch crack width.
Saw-cut cylinders with un-aged binder membrane, no chips (3
cores per binder)
Saw-cut cylinders with un-aged binder membrane and chips (3
cores per binder)
Saw-cut cylinders with aged binder membrane, no chips (3 cores
per binder)
Saw-cut cylinders with aged binder membrane and chips (3 cores
per binder)
Task 6: Conduct Tensile Testing on Test Specimens and Procure Data
Task 7: Analyze Data and Write Report
Project start date: July 1, 2002
Project end date: June 30, 2003
$80,000.00
The proposed project will fund one graduate student. The graduate students thesis research may include aspects relating to the project. This graduate student will participate in all areas relating to the project including; planning, scheduling, design, construction, selection of materials, data reduction and analysis and reporting of results.
At this time there is no known relationship to other reasearch projects of this nature.
Result of this project will be disseminated through a variety of mechanisms. Technical papers will be written and presented at conferences and seminar attended by state and municipal member and those in the transportation industry.
This project will provide users of chip seal treatments better methods with which to evaluate available chip seal systems. No known system currently exists.
Asphalt, modified crumb rubber asphalt, chemically modified crumb rubber asphalt & chip seal.