Accelerated loading evaluation of foamed asphalt treated RAP layers in pavement performance.

Details

• Creators:
  Mohammad, Louay N. ; Wu, Zhong ; King, William M.
• Corporate Creators:
  Louisiana State University. Dept. of Civil and Environmental Engineering
• Corporate Contributors:
  United States. Federal Highway Administration
• Subject/TRT Terms:
  • Pavement performance
  • Accelerated tests
  • Foamed asphalt
  • Recycled materials
  • Field tests
  • Laboratory tests
  • Base course (Pavements)
  • Wearing course (Pavements)
  • Moisture content
  • Ruts (Pavements)
• Publication/ Report Number:
  FHWA/LA.09/475
• Resource Type:
  Tech Report
• Geographical Coverage:
  Louisiana
• Corporate Publisher:
  Louisiana. Dept. of Transportation and Development
• Abstract:
  Due to a lack of locally produced high-quality stone base materials, the Louisiana Department of Transportation and Development (LADOTD) is ; continuously seeking alternative base materials in lieu of crushed stones used for roadway construction. This report documents the research efforts conducted ; at the Louisiana Transportation Research Center (LTRC) regarding foamed-asphalt treated reclaimed asphalt pavement (RAP) alternative base materials and ; provides detailed information on experiment design as well as conducted field and laboratory tests. ; An accelerated pavement testing (APT) experiment was conducted in this study using the Accelerated Loading Facility (ALF) at LTRC’s Pavement ; Research Facility (PRF) testing site. The APT experiment included three different base test sections: the first one contained a foamed-asphalt treated 100 ; percent RAP base course (FA/100RAP), the second used a foamed-asphalt treated 50 percent RAP and 50 percent recycled soil cement base course ; (FA/50RAP/50SC), and the third had a crushed limestone base. Despite using different base materials, the three APT sections shared other pavement layers ; and had a common pavement structure: a 2-in. asphalt wearing course, an 8.5-in. base course, and a 12-in. cement-treated subbase course over an A-4 soil ; embankment 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). To expedite traffic-induced pavement deteriorations, two steel load plates of 2,300-lb. each were ; added to the ALF load assembly (with a self-weight of 9,750-lb.) specifically at the loading cycle numbers of 175,000 and 225,000, respectively. The ; instrumentation data was collected at approximately every 8,500 ALF load repetitions; whereas, non-destructive deflection tests (NDT) and surface distress ; surveys (for surface rutting and cracking) were conducted at every 25,000 ALF load passes. In addition, a series of laboratory engineering performance-based ; tests was performed to characterize the performance of utilized materials in the APT experiment. ; The overall APT results generally indicated that the two foamed-asphalt base materials did not perform better than or as well as the crushed stone base. All ; three test sections were failed primarily due to the development of surface rutting. I isolated fatigue cracks were observed in localized areas of each test ; section associated with excessive surface ruts. The crushed stone section reached a rutting failure limit of an average rut depth of 0.5 in. approximately at an ; ALF loading cycle of 282,000; whereas, the FA/100RAP and FA/50RAP/50SC sections reached the limit at 230,000 and 228,000 repetitions, respectively. ; However, further analyses based on field measurement results revealed that both foamed-asphalt test sections showed slightly less permanent deformation ; than the crushed stone section during the first 175,000 ALF load repetitions. The backcalculated in-situ moduli of the two foamed-asphalt base courses were ; higher than that of the crushed stone base during the loading period when the applied ALF load was at 9,750 lb. Loading was increased after this and ; unfortunately, as the ALF load levels increased, both foamed-asphalt sections suddenly displayed a significantly higher rate of rutting than the stone section ; and quickly developed a premature rutting failure. ; A Shakedown theory analysis indicated that both foamed-asphalt treated RAP base materials seemed to have a lower shakedown threshold stress than the ; crushed stone base. It was due to the increase of the ALF load levels after the 175,000 repetitions that caused pavement base stresses higher than the ; shakedown threshold stresses of the two foamed-asphalt treated RAP base materials and eventually resulted in a stage of incremental collapse (or a sudden ; rutting failure) for the two foamed-asphalt test sections. In addition, the shakedown analysis also suggested that, as long as keeping the traffic induced stress ; level below the corresponding threshold stresses (as shown in the case when the ALF load was at a 9,750-lb. level), both foamed-asphalt base materials would ; have continuously performed better than the stone base. ; Due to having excellent performance under a 9,750-lb. ALF load, the foamed-asphalt treated RAP mixtures evaluated in this study may be considered for ; low volume roads, where the percentage of overloaded heavy truck traffic is relatively low and the environment is relatively dry (or a good drainage system is ; provided).
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• Format:
  PDF
• Funding:
  LTRC Project Number: 03-2GT: ALF-4 ; State Project Number: 736-99-1124
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/26819/dot_26819_DS1.pdf
• File Type:
  [PDF - 1.08 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha256:f3a73e62db1e6316e092ee06976d151c447e2810e32b32ac6b831e976a533c87