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Tolerable strains for hot mix asphalt overlays over concrete pavements.

File Language:
English


Details

  • Creators:
    Han, Jie ; Gautam, Ashwani ; Pokharel, Sanat K. ; Parsons, Robert L.
  • Corporate Creators:
    University of Kansas. Dept. of Civil, Environmental and Architectural Engineering
  • Subject/TRT Terms:
  • Publication/ Report Number:
    K-TRAN: KU-08-3
  • Resource Type:
    Tech Report
  • Geographical Coverage:
    Kansas
  • Edition:
    Final report.
  • Corporate Publisher:
    Kansas. Dept. of Transportation
  • Abstract:
    Due to change of temperature and/or moisture, freezing-thaw cycles, loss of subgrade support by erosion, and traffic loading, concrete ; pavements can develop different types of distresses during service life. Hot mix asphalt (HMA) overlays are commonly used to improve the ; serviceability of damaged concrete pavements. The most challenging issue for HMA overlays over concrete pavements is the development of ; reflection cracks through the overlays at the locations of joints and existing cracks on concrete pavements. Even though different techniques have ; been used to overcome this issue, they often do not yield satisfactory results and performance. Cracking of HMA overlays results from ; intolerable tensile strain and/or shear movement developed in the overlays due to the movement of concrete pavements. Limited studies have ; been conducted so far to determine the tolerable tensile strain and shear deformation of HMA overlays on concrete pavements. If the strain and ; shear deformation the HMA can endure are known, the methods that will limit or prevent that strain and deformation can be sought. This research ; experimentally determined the tolerable tensile strain and the relative shear movement of the HMA overlays. Direct shear tests and semi-circular ; bend tests of HMA specimens and HMA overlay loading tests under static and cyclic loading on gapped concrete blocks were conducted in this ; research. ; HMA materials from two Kansas Department of Transportation (KDOT) projects, namely 089 C-4318-01 (Mix 1) and 56-29 KA-1087- ; 01 (Mix 2), were used in the laboratory study. All testing was conducted at room temperature. Considering typical HMA overlay thicknesses used ; in Kansas, the selected thicknesses of the HMA overlays were 1.5 and 2.0 inches. Direct shear tests and semi-circular bend tests were conducted ; on these chosen HMA mixtures to characterize their shear and tensile properties respectively. Overlay loading tests were conducted on HMA ; overlays adhered to gapped concrete blocks to evaluate the interaction between the HMA overlays and the concrete blocks with a gap subjected ; to static or cyclic loading. Steel bars having a diameter of 0.25, 0.375, or 0.5 inches were used as spacers to create a gap in a direct shear test in ; the lab. These gaps simulate joints in concrete pavements. Measured relative shear displacements of these HMA specimens at failure varied from ; 6.0 % to 9.0 % of the specimen thickness depending upon the simulated gap width. Tolerable tensile strains of Mix 1 specimens under fatigue ; loading in the semi-circular bend tests were from 1.2% to 4% while those of Mix 2 specimens were from 0.6% to 1.4%. Test results show that the ; compressive load capacity of a specimen under the semi-circular bend test was linearly correlated to the shear load capacity of the specimen at ; the same mix and thickness under the direct shear test. Specimens at the onset of cracking in the overlay loading tests had the permanent vertical ; displacements with similar magnitudes as the shear displacements corresponding to the shear load capacities in the direct shear tests. The ; tolerable tensile strains of HMA specimens in the overlay tests were smaller than those in the semi-circular bend tests; however, an increase of ; the applied load or gap width minimized their differences. The overlay loading tests showed that the cracking could be avoided if the tensile ; strains in the HMA overlays were less than 0.5%. ; Based on the HMA mixes, the specimen thicknesses, the gaps between the concrete blocks, the load levels, and the test temperatures ; used in this research, it can be concluded that: (1) the shear failure could be avoided if the shear deformation of the HMA overlay was less than ; 6% of the overlay thickness and (2) the cracking could be avoided if the tensile strain in the HMA overlay was less than 0.6%. The methods that ; will limit or prevent reflection cracks due to shear deformation and tensile strain should be sought in a future study.
  • Format:
    PDF
  • Funding:
    C1727
  • Download URL:
    https://rosap.ntl.bts.gov/view/dot/25499/dot_25499_DS1.pdf
  • File Type:
    Filetype[PDF - 4.17 MB]
  • Collection(s):
    US Transportation Collection
  • Main Document Checksum:
    urn:sha-512:22d293e1761057ba2447977083b1f18ecec5d3f182d710aa60abcb2ec5846e5a394fdae4840b5a1619ef434a6453d3c97323d61e84b49a703a5105a69b66ee47
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