Accelerated loading evaluation of stabilized BCS layers in pavement performance.

Details

• Creators:
  Wu, Zhong ; Zhang, Zhongjie ; King, William M.
• Corporate Creators:
  Louisiana Transportation Research Center
• Corporate Contributors:
  Louisiana. Dept. of Transportation and Development ; United States. Federal Highway Administration
• Subject/TRT Terms:
  • Accelerated tests
  • Deformation
  • Pavement performance
  • Base course (Pavements)
  • Testing
  • Test procedures
  • Evaluation
  • Performance measurement
  • Roads--Louisiana--Base courses--Testing
  • Roads--Louisiana--Base courses--Evaluation
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• Publication/ Report Number:
  FHWA/LA.08/474
• Resource Type:
  Tech Report
• Geographical Coverage:
  Louisiana
• Edition:
  Final report; 2005-2008.
• Corporate Publisher:
  Louisiana Transportation Research Center
• Abstract:
  BCS is short for blended calcium sulfate, a recycled fluorogypsum mixture that has been used in Louisiana as a roadway base for more than a decade. ; Without further chemical stabilization, the major concern of using raw BCS as a pavement structural layer is its moisture susceptibility. ; In order to verify the efficiency of laboratory-derived BCS stabilization schemes and further assess related field performance and potential cost ; benefits, an accelerated pavement testing (APT) experiment was recently conducted at Louisiana Transportation Research Center (LTRC) using the ; Accelerated Loading Facility (ALF). The APT experiment included three different base test sections: the first one contained a granulated ground blast ; furnace slag stabilized BCS base course (called BCS/Slag), the second used a fly ash stabilized BCS base course (called BCS/Flyash), and the third had a ; crushed limestone base. Except for using different base materials, the three APT sections shared a common pavement structure: a 2-in. asphalt wearing ; course, an 8.5-in. base course, and a 12-in. lime-treated working table layer over an A-6 soil subgrade. Each section was instrumented with one multi-depth ; deflectometer and two pressure cells for measuring ALF moving load induced pavement responses (i.e., deflections and vertical stresses). The ; instrumentation data were collected at approximately every 8,500 ALF load repetitions; whereas, non-destructive deflection tests and surface distress ; surveys (for surface rutting and cracking) were performed at every 25,000 ALF load passes. ; The accelerated loading results generally indicated that the test section with a BCS/Slag base course outperformed the other two APT sections (i.e., the ; BCS/Flyash and the crushed stone sections) by a large margin. This was evidenced by all measurements in surface deflection, vertical compressive stress, ; rutting resistance, and pavement life. Post-mortem trench results revealed that the BCS/Slag base performed just like a lean concrete layer inside the ; pavement without any moisture-induced damage issues. The backcalculated layer moduli of the BCS/Slag base ranged from 1,190 ksi to 2,730 ksi, much ; higher than that of an asphalt concrete layer. In addition, the BCS/Flyash test section performed significantly better than the crushed stone test section in ; terms of the load carrying capacity, rutting resistance, and pavement life. However, post-mortem trench results showed a shear failure initialized inside the ; BCS/Flyash base layer on a failed station of the corresponding test section. Whether or not such a shear failure is indicative of a long-term moisturesusceptibility ; problem for the BCS/Flyash base layer, especially under a constantly wet environment, remains a concern due to the relatively short loading ; period associated with any APT experiment. Based on APT results, it was estimated that structural layer coefficients for the BCS/Slag and BCS/Flyash ; base courses used in this APT study would be 0.34 and 0.29, respectively. ; A cost-benefit analysis showed that the implementation of a slag stabilized BCS base in lieu of a crushed stone base will lead to a thinner asphalt ; pavement design, which can result in an initial construction cost reduction up to 16 percent without compromising future pavement performance. On the ; other hand, a 30-year life cycle cost analysis (LCCA) based on a typical Louisiana low volume road pavement structure indicated that using an 8.5-in. slag ; stabilized or 8.5-in. fly ash stabilized BCS base course, in lieu of a 8.5-in. crushed stone base, will potentially result in an LCCA cost savings up to 62 ; percent and 56 percent per lane mile, respectively. ; Overall, it is concluded that both the slag and fly ash stabilized BCS materials evaluated in the study should be a good base material candidate for a ; flexible pavement design in Louisiana. However, caution should be made when using a fly ash stabilized BCS base under a constantly wet environment.
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• Format:
  PDF
• Funding:
  03-2GT
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/24053/dot_24053_DS1.pdf
• File Type:
  [PDF - 1.39 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:ddc6711e33ffe6fbe601118474e36bfa3aceecf561b5e9756b7dd043f52fce2ae715b5b4660b9c8149fa6be45cbf77149a81f8859637ae224ae4fa9cc3d0a091