Vegas hits the jackpot

Case Studies
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Only a lucky few hit the jackpot on the Las Vegas Strip. But the city of Las Vegas found an innovative product that allowed them to do just that along Washington Avenue. Originally constructed almost 30 years ago and rehabilitated in 1992, Washington Avenue is a four lane arterial with approximately 18,000 vehicles in average daily traffic, 2.8% of which are trucks.

In 2006, the city of Las Vegas determined it was time to reconstruct the road because of low pavement quality index and structural numbers. Instead of their standard reconstruction methods, they looked for something that could improve the structure of the road and save money.

The solution was Fortress granular base stabilization (GBS) . Fortress GBS consists of an engineered mix design, performance-related specifications and an innovative asphalt emulsion to produce a flexible base that is strong enough for traffic before surfacing and improves crack resistance and moisture susceptibility. The city became interested in the process because it uses standard construction equipment and is a relatively shallow treatment, which allowed minimal impact on utilities.

The condition of the 1-mile stretch of pavement along Washington Avenue varied and contained moderate to severe fatigue and block cracking. The hot-mix asphalt (HMA) depth ranged from 4 to 6 in. and the aggregate base averaged 15 in. Reducing this variability was one of the city’s goals so that there would be more options to maintain the roadway in the future.

Prior to construction, a number of tests were performed on Washington Avenue to assess its strength and layer thicknesses. Stantec performed falling-weight deflectometer (FWD), ground-penetrating radar and dynamic-cone penetrometer testing. Samples taken from Washington Avenue were used to perform the engineered mix design in SemMaterials’ laboratory in Tulsa, Okla.

Southern Nevada Paving, the project contractor, removed 5 in. of HMA with its Caterpillar RM-350 road reclaimer prior to stabilizing Washington Avenue. This stabilized 6 in. of material with emulsion supplied from SemMaterials’ Fontana, Calif., plant. The emulsion was added using the Caterpillar reclaimer.

The reclaimer was followed by an Ingersoll Rand steel-wheel roller and an Ingram pneumatic roller to achieve the density specifications.
The eastbound lanes were constructed first and remained closed until they were overlaid with 5.5 in. of HMA. The westbound lanes were then stabilized, compacted and overlaid.

Postconstruction FWD testing indicated a significant improvement. The effective structural number increased 53% at five separate locations. The postconstruction effective structural number ranged from 4.31 to 5.49, above the design requirement of 4.2.

The city saved over $300,000 by using Fortress GBS and was able to rehabilitate two additional miles with a thick lift mill and overlay last year. Construction time was shortened by 80 days, and 3,000 fewer loads were trucked on and off the project.

Overlay Init