Performance of Michigans Stabilized Base Projects

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Performance of Michigans Stabilized Base Projects
Andy Bennett, MDOT Will Hansen, UM Dave Smiley,
formerly MDOT
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Background

• Before 1984 MDOT used a dense-graded base design
  without drainage systems.
• Over time, poor base drainage led to premature
  joint deterioration and faulting (roughness) at
  joints and cracks from the movement of base fines
  under high pore pressures (from heavy wheel
  loads) directly under the pavement slab (JRCP)

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Background

• MDOT started experimenting in 1990 with recycled
  aggregate for base coarse. The primary purpose of
  the treatment was to coat the aggregate
  particles, if crushed concrete from the old
  pavement was used, to prevent any leaching
  concrete residue from clogging the drainage layer
  or the internal drainage system. A secondary
  benefit was to provide stability to the aggregate
  matrix, which was a gap-graded gradation (5G)
  that was selected to enhance drainage.

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Special Provision for Stabilized Open Graded
Drainage Coarse

• Contractors had a choice of stabilizing with
  asphalt cement, asphalt emulsion, or cement .
• Cement content for stabilization called for
  approximately 6 (190 lbs/CYD).
• Asphalt stabilization option called for
  sufficient stability and coating of the surface
  particles (approximately 3).
• Aggregate gradation 5G obtained only from crushed
  concrete from the project.

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Stabilized Base Projects

• 13 projects were constructed with 4 stabilized
  base between 1990 and 1995.
• 2 projects were stabilized with cement and 11
  projects with asphalt.
• Asphalt emulsion was used on the majority of
  projects because it was less expensive.

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Background MDOT Base Gradations
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Construction Concrete
Crushing Operation
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Construction-Pug Mill Emulsion Coating (ATB)
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Stabilized Bases as Constructed
6 cement treated base
Asphalt emulsion treated base
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Construction- CTB Project Paving
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2006 Field Investigation
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Excessive Joint Deflection Leading to Top-Down
Transverse Cracking
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Typical Distress Developmentfor JRCPs on
Treated versus Untreated Open-Graded Bases
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Performance Modeling Using Distress Index
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Performance Modeling Using Distress Index
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Comparison of Distress Between Treated and
Untreated Base Projects Constructed 1990-95
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Joint Deflection Treated vs Untreated Base
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Agg Test Road-27 ft JRCP 10.5 inch Concrete on 4
inch ATB
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Agg. Test Road-Section B
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Dowel-Bar Action
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SB US-23 Agg.Test Road-Section A Surface Profile
showing joint Settlement-Agg
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WB I-94, CS 82021, Belleville, 27 Ft JRCP 11
inch Concrete 4 inches CTB
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Cost Comparison of Open Graded Drainage Coarse

• I-94WB Wayne Co., 4 cement coated recycled 5G,
  393,000 SYDs _at_ 2.35/SYD, constructed 1992
• I-96 Howell, 4 asphalt emulsion coated recycled
  5G, 360,000 SYDs _at_ 1.35/SYD, constructed in
  1991-1992
• I-75 Wayne Co., 4 asphalt emulsion coated
  recycled 5G, 464,000 SYDs _at_ 1.90/SYD,
  constructed in 1991
• I-69 Eaton Co., 5 3GM1 (not recycled concrete),
  457,000 STDs _at_ 3.20/SYD (project 21823A)
  346,000 SYDs _at_ 2.70/SYD (project 21824A)
  307,000 SYDs _at_
  2.69/SYD (project 21825A)
  166,000 SYDs _at_ 2.69/SYD (project 21826A)
  Projects constructed between
  1991 and 1993

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Major Findings

• JRCP on Treated base (ATB/CTB) OGDC was found to
  have improved joint stability (smaller joint
  deflection) as compared to JRCP on untreated
  base. Consequently, a reduction in top-down
  transverse cracking developed during the
  time-period studied (15 years) with no upward
  trend in distress index.
• Excessive joint deflection developed in JRCP on
  untreated 3G (MDOT gradation) OGDC requiring
  maintenance within 15 years.

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Findings contd

• Poor sub-surface drainage condition was
• found to promote permanent joint settlement in
  some of the stabilized base projects.

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Findings contd

• In slag concrete dowel-bar looseness
  develops as the coarse aggregate cannot maintain
  joint load transfer through dowel-bar action.
  Almost all joint load transfer through dowel-bar
  action is lost within the time period studied.
  This has promoted mid-slab transverse cracking as
  seen from the Aggregate Test Road results.

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Recommendations

• Stabilized base-course can be expected to
• improve performance of jointed plain concrete
  pavement (JPCP) for Michigan conditions of
  traffic and wet-freeze climate.