The Effect of Asphalt Concrete Overlays on The Progression of Durability Cracking in Portland Cement Concrete (d-Cracking, Frost, Freeze-Thaw, Autogenous Healing)
Janssen, Donald James
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https://hdl.handle.net/2142/69954
Description
Title
The Effect of Asphalt Concrete Overlays on The Progression of Durability Cracking in Portland Cement Concrete (d-Cracking, Frost, Freeze-Thaw, Autogenous Healing)
Author(s)
Janssen, Donald James
Issue Date
1985
Department of Study
Civil Engineering
Discipline
Civil Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Civil
Abstract
Durability Cracking (D-cracking) is the progressive deterioration of Portland cement concrete (PCC) and is normally caused by winter freeze-thaw cycling. The PCC coarse aggregate source has been identified as causing well designed mixes to develop D-cracking.
A common rehabilitation procedure for D-cracked PCC pavements is to overlay the PCC with asphalt concrete (AC). This renews the surface, but little is known about the long term effect of AC overlays on D-cracked PCC pavements. Specifically, will an AC overlay stop the progression of D-cracking, or accelerate it.
The primary climatic factors responsible for D-cracking are moisture and temperature. Finite-difference transient flow computer moisture movement modelling as well as field instrumentation and laboratory measurements indicated that AC overlays have negligible effect on the PCC pavement moisture regime. This is due to the extremely low hydraulic conductivity of PCC. Evaporative drying of the PCC extends less than 2 in. into the PCC pavement.
The effect of AC overlays on the PCC temperature regime was evaluated by finite-difference heat transfer computer modelling. AC overlays were found to decrease the number of freeze-thaw cycles and the rate of cooling in PCC pavements. The cooling rate at the top of an 8-in. PCC pavement in the St. Louis, Missouri area was decreased from 1.19 to 0.24 F(DEGREES)/hr by a 4-in. overlay.
Laboratory freeze-thaw durability tests duplicating field conditions for Interstate 70 near Vandalia, Illinois were conducted. The laboratory PCC samples were made with the same coarse aggregate as the D-cracked I-70 pavement section. The samples had either no overlay, or 2-, 4-, or 6-in.overlays. A freeze-thaw cycle determined from actual climatic data was used to simulate winter freeze-thaw cycling. All of the PCC samples cycled to the equivalent of 5 years of winter exposure showed strength loss as determined by split tensile tests. The samples with 4-in. overlay showed the most strength loss.
It was concluded that AC overlays do not prevent the progression of D-cracking in PCC; instead some overlay thicknesses accelerate the deterioration. When AC overlays are designed for D-cracked PCC pavements, the effect of decreasing strength of the deteriorating PCC should be considered.
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