Hawaii's First SMA Project

Never one to back away from new technology, Grace Pacific Corp. is undertaking the State of Hawaii's first Stone Matrix Asphalt Pavement (SMA) project. The Moanalua Freeway project is being done simultaneously with the Interstate H-1 rehabilitation project. Hawaiian Dredging and Construction Co. is the general contractor of the $14.6-million project, with Grace Pacific serving as the paving subcontractor.

The asphalt contractor's $5.2-million portion of the project involves milling 3 1/2 inches off 23 lane miles of the existing road where the two-inch SMA mat is placed, milling 16 lane miles where the 1 1/2-inch State IV Mix mat is placed, and milling off 15 lane miles where the two-inch Superpave mat is placed.

The Hawaii DOT is using the 5-mile construction project to compare the performance characteristics of SMA and Superpave mixes on designated portion of the four-lane roadways. One of the unique features of these two projects is that the Moanalua Freeway is federally funded, while the H-1 project is 100-percent state financed.

Moanalua Freeway was built in the late 1960s, and was one of the main corridors to Honolulu from the outlying areas to the west. The area is filled with Hawaiian history because it was one of the most populated areas during the monarchy period, and it holds a wealth of cultural significance for native Hawaiians.

A question many ask is "How can you have an interstate highway on an island?" The answer is that the Interstate Highway System is actually a system of interstate and defense-access highways, and H-1 qualifies as such, since it linked the Army's Schofield Facility to Pearl Harbor, where the Arizona Memorial is located, and also now the USS Missouri.

Scope of work

The project includes installation of SMA and Superpave asphalt concrete pavement on both the inbound and outbound lanes of Moanalua Freeway; installation of Ultra Thin White topping (two inches of Portland cement concrete) at Ramp B, resurfacing pavement; and reconstructing weakened pavement areas.

Three miles of the four-mile Moanalua portion of the project calls for SMA produced with a PG 70-22S AC binder, and the remaining one mile, as well as the H-1 portion, being constructed of a Superpave mix calling for a PG 64-16 AC binder. Approximately 42,000 tons of HMA will be produced for the project.

The project is being done at night approximately five miles in length. The cold planning and resurfacing work will be utilizing three Roadtec RX-60C cold planers, two with the standard 7.25-foot cutting head, and one with a 12-foot cutting head. The cold planers will be followed by a paving train consisting of a 2500 Roadtec Shuttle Buggy, feeding a new Roadtec RP-190 rubber tire paver with an E-10B electric heated screed. Two C-784 high frequency vibratory Hypac tandem rollers with the vibratory frequency set at 4,000 vpms, and a 13-ton vibratory roller in the static mode will do the compacting.

To produce the mixes, Grace Pacific will be using either an Astec eight-foot double-barrel plant purchased in 1992, or the company's newest plant facility that houses an Astec seven-foot double-barrel equipped with a CEI asphalt mixing and storage tank.

To produce the binder, Grace Pacific partnered with Wright Asphalt from Texas, who shipped the polymer concentrate in special hot oil heated bulk containers from their facility in Portland. Grace Pacific also incorporated an automated feeder that introduces fiber to the mix.

Working with SMA

On June 10 the asphalt contractor ran its first SMA test strip for the project using the paving train that was mentioned earlier, and achieved compaction results of 94 percent. At first, the mix was sticky to work with and the temperature was inconsistent.

The rolling technique employed on the test strip used one Hypac C-784 high frequency roller set at 4,000 vpms, with a 10-ton vibratory roller operating in a static mode following the Hypac. The paving crew and plant operators also recognized the mix used for the test strip was not as hot as it needed to be for proper compaction. This was due primarily to the limited production (100 to 200 tons) required for the test strip, but was easily remedied once the plant was up to full-production.