Details:

Creators:
Han, Jie ; Gautam, Ashwani ; Pokharel, Sanat K. ; Parsons, Robert L.
Han, Jie ; Gautam, Ashwani ; Pokharel, Sanat K. ; Parsons, Robert L. Less -
Corporate Creators:
University of Kansas. Dept. of Civil, Environmental and Architectural Engineering
Subject/TRT Terms:
[+]
Cold Weather Concrete Pavements Freeze Thaw Durability Hot Mix Asphalt Load Tests Overlays (Pavements) Pavement Cracking Pavement Distress Pavements, Concrete--Cracking Pavements, Concrete--Effect Of Temperature On Pavements, Concrete--Testing Pavements--Overlays Shear Tests Strain (Mechanics) Tensile Strength Tension
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
Collection(s):
US Transportation Collection
Main Document Checksum:
[+]
urn:sha256:91d42db2d69da1900f7ab9f7b72570e0ee8de265d95a1fb4eedb2f4485c6f818
Download URL:
https://rosap.ntl.bts.gov/view/dot/25499/dot_25499_DS1.pdf
File Type:

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