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Publication Number: FHWA-RD-02-083
Date: August 2006

Appendix B

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The test sections in Ohio were diamond ground between construction and the first monitoring visit (figure B1), so no evidence of surface scaling was visible. However, the diamond-ground surface did not experience any deterioration.

Figure B1. Typical surface textures after diamond grinding, Ohio test sections.

This is a black-and-white photograph of a section of pavement. On the left side of the pavement is a gap approximately 30 millimeters wide. On the bottom of the pavement is a white paint strip. There are three indented rectangles, approximately 75 millimeters tall by 40 millimeters wide, with the numbers 1, 4, and 7 stamped in them, near the bottom of the pavement. There are horizontal grooves throughout the surface. There was no evidence of scaling, and the diamond ground surface did not experience any deterioration.

Nondestructive testing of the existing D-cracking susceptible concrete was conducted adjacent to the treated (or untreated) joints using Spectral Analysis of Surface Wave (SASW) methods. A schematic of the SASW test method is shown in figure B2. Actual testing at the Ohio test sections is shown in figure B3.

Figure B2. Schematic diagram of SASW testing (from Malhorta and Carino,Handbook on Nondestructive Testing on Concrete, CRC Press, New York, 1991.)

On the top right of this figure is a box representing the spectral analyzer. The spectral analyzer extends down to two receivers on the right section of a rectangular figure. Receiver 1 is on the center of the rectangular figure, and receiver 2 is on the right side. The distance between the two receivers is the X variable. The distance from one receiver to the center distance between the two receivers is 0.5 X. On the top left section of the rectangle is a hammer. Spreading away from the hammer’s impact is the R-wave. The distance from the hammer to the first receiver is lowercase D greater than X.

Figure B3. SASW testing at the Ohio test sections.

This figure is a black-and-white photograph showing the trunk of a car and the pavement. The spectral analyzer is in the trunk, and two wires are attached to it and to the pavement for testing. There are signs pointed at the wires that read "Accelerometer."

The method involved impacting the surface of concrete in such a way as to maximize the production of surface waves (R-waves) while minimizing the compression waves (P-waves). Two accelerometers mounted in line about 75 mm from the joint were used to measure the Rwave vibrations. Analysis of the phase shift of the vibrations between the two accelerometers was used to determine the R-wave velocity for various vibration frequencies. High-frequency vibrations are representative of shallow depths, while lower frequencies are more influenced by materials at greater depths in the pavement.

Figure B4 shows a typical R-wave velocity versus vibration frequency plot. The concrete pavement and subbase (base) portion are easily identified. The central section of the graph is dominated by noise resulting from waves reflected by the vertical edge of the pavement. This phenomenon is present in most of the R-wave velocity versus vibration frequency plots from the Ohio testing. Extensive analysis was conducted to filter out this reflection noise from the digital data obtained in Ohio.

Figure B4. Typical R-wave velocity versus vibration frequency plot.

In this graph, frequency is graphed on the horizontal axis from 2,000 to 5,500 hertz. Velocity is graphed on the vertical axis from 0 to 4,000 meters per second. The first part of the graph, to the left, shows the base portion. The wave begins at a frequency of 2,000 hertz and 900 meters per second. The wave increases gradually to 3,000 hertz at 1,500 meters per second. The next portion shows the reflection noise. The wave drops suddenly and then increases sharply between 3,500 to 4,500 hertz. The wave then gradually levels out at 1,850 meters per second after 4,750 hertz, in the concrete portion.


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