In September 2011, Ames Engineering of Ames, Iowa conducted profile testing of three lanes of I-290 between Austin Blvd. and Sacramento Blvd. in both directions. Previously, in 2010, this section of roadway had both a Stone Matrix Asphalt (SMA) overlay and a Conventional Diamond Grinding (CDG) surface constructed. The profile testing was conducted to compare the SMA ride qualities to the CDG ride qualities.
In the summer of 2010, Project ACIM-290-4(118)091 was constructed between Austin Avenue and Sacramento Blvd. in both directions. The project, which extended for approximately 3.8 miles, consisted of overlaying three to four lanes of the existing plane jointed Portland Cement Concrete Pavement (PCCP) roadway in each direction with SMA from Austin Avenue to Kostner Avenue and from Homan Avenue to Sacramento Blvd. CDG was used to retexture the existing Continually Reinforced Concrete Pavement (CRCP) pavement between Kostner Avenue and Homan Avenue. A joint venture between Quality Saw and Seal, and Safety Grooving and Grinding, provided the diamond grinding in July of 2010.
In 2010, the project was evaluated for tire/pavement noise shortly after completion of the diamond grinding using an On Board Sound Intensity (OBSI) noise measurement device. The CDG and SMA surfaces were comparable in noise level with the CDG registering at 103.7 dBA and the SMA at 103.4 dBA.
The diamond grinding on this project received an award for its ride quality, which prompted the International Grooving & Grinding Association (IGGA) to conduct profile testing of both the SMA and CDG surfaces to enable a comparison of the ride characteristics. Ames Engineering was hired to conduct profile testing of the project.
Conducting Profile Testing
On Sept. 29, 2011, Ames Engineering conducted profile testing on I-290 between Austin Boulevard and Sacramento Avenue. Both the eastbound and westbound directions were tested to compare the smoothness levels of a diamond ground section to the SMA overlay, both of which were constructed during the summer of 2010 on a single IDOT construction project.
Testing was completed during a single night. The outside lanes were tested in both directions. The westbound testing was initiated at the Sacramento Avenue overpass and terminated at the new overlay terminus just east of the Austin Avenue overpass. The eastbound testing commenced at the Austin Avenue overpass and terminated at the Sacramento Avenue overpass.
I-290 varies between three lanes and four lanes in each direction; three lanes of which are continuous through the project. The fourth lane departs near Austin Avenue.
The Ames Engineering profile van measured the profile in each wheel path simultaneously. Two RoLine sensors were mounted on a cross member which attaches to the front bumper. The RoLine sensors were positioned approximately 12 inches above the pavemet. The RoLine footprints were positioned 72 inches apart (center to center).
At the same time that profile measurements were obtained, still photos were taken at approximate 150 feet intervals allowing correlation between the profile results and a roadway image. The image was captured using a camera mounted to the windshield just below the rear view mirror. Both the images and profile data were linked to GPS coordinates.
“Ames tested with a state-of-the art wide band profiler, which is the most accurate method of testing,” said Scott Eilken, owner of Quality Saw & Seal. “It doesn’t get any better than that.”
The CDG surface had an overall average profile index (zero blanking band) of 20 inches/mile with a standard deviation of 3.9 inches/mile while the SMA exhibited an overall average of 23.1 inches/mile and a standard deviation of 6.3 inches/mile. While 90 percent of the CDG surface exhibited a profile index of 25 inches/mile or less, only 61% of the SMA surface achieved this. Additionally, while 100% of the CDG surface can meet a requirement of 30 inches/mile, 10% of the SMA surface would still exceed this limit.
The results indicate that the CDG surface was smoother than the SMA overlay by approximately 3 inches/mile and that the smoothness variability was approximately half that of the SMA surface. With the increased emphasis worldwide toward safe, smooth and low noise pavement surfaces, CDG has proven to be an economical and environmentally safe choice for today’s roadway specifiers. The traveling public and surrounding communities will notice the reduction in tire/pavement noise while the transportation authorities will benefit from the safe, smooth and lo
“This testing proves what this industry has known for a long time. A 20- to 25-year-old concrete pavement can be made smoother for less money using diamond grinding when compared to an asphalt overlay and avoids the never-ending cycle of milling and overlay brought on by covering a structurally sound section of concrete pavement,” said Eilken.
This article was contributed by John Roberts, executive director of the International Grooving and Grinding Association (IGGA).