Interlayer stress absorbing composite (ISAC) for mitigating reflection cracking in asphalt concrete overlays
Mukhtar, Muhammad Tahir
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Permalink
https://hdl.handle.net/2142/20128
Description
Title
Interlayer stress absorbing composite (ISAC) for mitigating reflection cracking in asphalt concrete overlays
Author(s)
Mukhtar, Muhammad Tahir
Issue Date
1994
Doctoral Committee Chair(s)
Dempsey, Barry J.
Department of Study
Civil and Environmental Engineering
Discipline
Civil Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Civil
Language
eng
Abstract
"This study deals with the design of a composite material which could effectively alleviate/mitigate the problem of reflection cracking in an AC overlay. After reviewing various case histories and having identified the problem areas in the treatments currently in use, a composite material consisting of two geotextile layers containing a thin viscoelastic rubber asphalt layer named, ""Interlayer Stress Absorbing Composite (ISAC)"" was proposed."
To approach the design problem of the ISAC system effectively properties of the materials intended to be used in the system were first identified. Various models and laboratory testing procedures were used for this purpose. A Climate-Materials-Structural (CMS) pavement model was used to establish the pavement temperature range in Northern Illinois. A number of geotextiles were selected and tested for their engineering properties. Several samples of rubber asphalt were prepared by blending various ratios of crumb rubber with different types and ratios of asphalt cements. These materials were tested at different temperatures and the effects of temperature and rate of deformation on stiffness were investigated.
"After having selected the materials suitable for the ISAC system, based on their properties, a prototype ISAC system was fabricated in the laboratory and was then checked against slippage under an overlay with a vehicle making a sharp turn or applying sudden brakes. The computer program ""CIRCLY"" was used for this purpose. Testing equipment was developed to evaluate the interfacial shear strength and laboratory testing was performed to determine the shear strength of the fabricated ISAC layer under an AC overlay. Required stiffens was achieved in the ISAC core material by adding hydrated lime in the rubber asphalt."
After completion of the component property testing program, the ISAC layer was fabricated and prepared for laboratory evaluation. A testing device was developed in the laboratory that simulated field conditions to evaluate an AC overlay over a cracked PCC slab with and without an ISAC system. The performance of the ISAC system was evaluated by comparing crack growth in the overlay of a control pavement section with that in an overlay over the ISAC treated PCC slab.
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