Evaluation of Superpave Shear Test Protocols
Author(s):
A. Chowdhury, J.W. Button
Publication Date:
January 2002
Abstract:
The Strategic Highway Research Program (SHRP) study, during the development of the Superpave mixture design and analysis process, provided a series of test protocols using the Superpave shear tester (SST) to predict the performance of the hot mix asphalt (HMA) mixtures. Excessive time is required to conduct all of these test procedures on each HMA mixture designed, which can significantly increase the cost of mixture design. Conducting all of the tests can be confusing and even conflicting. The objective of this study is to evaluate four selected Superpave shear test protocols and determine which of the test protocols is most suitable for predicting asphalt pavement performance.
The predominant pavement performance of interest herein is rutting. So, the ultimate goal is to identify the "best" SST test protocol that can evaluate the shearing resistance of HMA.
Researchers selected or developed four different mixtures from very poor to excellent quality using materials from Texas and Georgia.
The HMA mixtures selected for this study were : Type C limestone, Type D rounded river gravel, granite stone mastic asphalt (SMA), and granite Superpave. Rutting performance of these mixtures was evaluated using four SST protocols: Frequency Sweep at Constant Height (FSCH), Simple Shear at Constant Height (SSCH), Repeated Shear at Constant Height (RSCH), and Repeated Shear at Constant Stress Ratio (RSCSR).
Three laboratory-scale accelerated loaded wheel tests were performed on these four mixtures to compare the results with those from the SST. The loaded wheel tests used in this study were: Asphalt Pavement Analyzer, I/3-Scale Model Mobile Load Simulator, and Hamburg Wheel Tracking Device.
Researchers recommended the FSCH test as the "best" SST protocol. To determine the precision of the FSCH test, compacted specimens from three HMA mixtures were sent to six different laboratories across the US to conduct an interlaboratory test program.
Report Number:
0-1819-1
Electronic Link(s):
Document/Product
http://tti.tamu.edu/documents/1819-1.pdf
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