In 1993, the heavily traveled intersection of Routes 40 and 213 (originally constructed of concrete, then overlaid many times with HMA using standard SHA mixes) topped the SHA’s list of “trouble spots”. The heavy traffic at the signalized intersection was causing significant pavement deformation (in excess of one inch per year). Milling of the roadway’s high spots was being required once or twice each year, with a resurfacing needed frequently. In total, the intersection was costing SHA approximately $30,000 every two years just for maintenance. U.S. 40 at Landing Road was experiencing similar difficulties.

The Challenge
"We''ve heard all the rhetoric; now show us results."

The Maryland State Highway Administration approached both the asphalt and concrete industries asking them each to come up with a solution using their best technologies to solve the problem. That in essence, was the challenge given by SHA to the Hot Mix Asphalt (HMA) and Portland Cement Concrete (PCC) industries in 1993 for the rehabilitation of the two adjacent heavily traveled (30,000 ADT) intersections. U.S. Route 40 at Maryland Route 213 (HMA) and U.S. Route 40 at Landing Road (PCC) in Cecil County, Maryland. Each industry was free to select its own proposed solution without being constrained by existing specifications to which each industry responded with its “best” approach.

THE HMA RESPONSE The HMA industry responded by forming a team comprising the Maryland Asphalt Association (MAA), National Asphalt Pavement Association (NAPA), and the Asphalt Institute (AI). Following a visual inspection, test cuts, and core sampling of the existing intersection pavement, the team decided to mill off the existing pavement (up to eight inches in some places), and utilize the new mix design system known as Superpave (Superior PERforming asphalt PAVEments), developed from the five year, federally financed Strategic Highway Research Program (SHRP). Using the Superpave Performance Grade (PG) binder system, the average maximum pavement temperature and minimum design pavement temperature was established.

After considering all the factors (traffic weight and volume, both moving and standing, climate, etc.), a PG 76-22 asphalt cement (AC) binder was selected by the team.

THE PCC RESPONSE The Concrete Industry’s solution consisted of a 6 1/2” “whitetopping” system.

HMA MIX DESIGN Several prototype mix designs were developed and extensively tested in the laboratory before the final design was selected. For the 25mm base mix, an AC content of 4.4 percent was used, with the 19mm surface mix using 4.9 percent AC. The trap rock aggregates selected were standard AASHTO sizes combined with a C33 concrete sand. Air voids in the base mix tested out at less than 4.0 percent, with the surface mix averaging 5.8 percent.

HMA CONSTRUCTION Reconstruction work began in August of 1994, with milling off of up to eight inches of previously placed HMA overlays down to the original nine inch concrete pavement. Five inches were milled off the right lane, two inches were taken off a 500 foot section of Route 40 west bound travel lanes, and milling was also done on Route 213 approaches. To minimize traffic delays, work was constrained to the nighttime hours of 7:00p.m. to 6:00a.m., Sunday through Thursday. The Route 40 HMA mixes were placed by contractor T. C. Simons, Inc., of Fallston, MD in three lifts: two three inch base course lifts and one two inch surface lift. Rolling and compaction was done with one vibratory roller (one pass with both drums vibrating, the second pass with both drums static) and a finish roller (static) making one pass.Compaction achieved was almost 94%. Pavement ends were tapered at the end of each night’s work for traffic safety, keeping all lanes open to traffic during the daytime, and minimizing traffic disruptions to roadside businesses.

HMA LED THE WAY

CONSTRUCTION TIME
The HMA industry placed approximately 5,000 tons of Superpave mix (about 15,000 square yards) in five nights (three additional nights were used milling off and removing the old pavement). Work on the HMA section (including lane markings and traffic detectors) was completed in just eleven evenings and well ahead of the deadline set by the SHA due to an upcoming Labor Day holiday.

TRAFFIC DELAYS
Thru traffic on the HMA section was maintained at all times throughout the project’s duration, as was access to the many business establisments located at and near the intersection.

THE COST
For the HMA section, the in place cost per square yard was only one third the cost of the concrete section.

THE BOTTOM LINE
With traffic volumes after six years increasing to approximately 35,000 ADT (about 15 percent trucks), the HMA section has deformed less than three tenths of an inch (about the thickness of a coin) as measured at the end of 1999 by the Maryland SHA’s Automatic Road Analyzer (ARAN) pavement measuring device. Maryland Asphalt Association and its members can help design and supply“Superpave”.

"End of Challenge!"
THE PCC HEADACHE

CONSTRUCTION TIME
The concrete section was constructed in1995. Although addressing an area only one eighth the size of HMA’s, the concrete industry, worked around the clock, placing 1,800 square yards of concrete. Construction took 12 full days and nights, or more than twice the time it took for the HMA industry to completely construct its area.

TRAFFIC DELAYS
During construction of the concrete section, traffic lanes were closed for days at a time and access to business establishments was severely constricted.

THE COST
The cost per square yard for the concrete work was three times that of HMA. Naturally road user delay costs were also significantly higher for the concrete intersection.

THE BOTTOM LINE
The concrete section? It began cracking in 1998, only three years after construction. In July 2000 it was completely removed and replaced with an HMA “Superpave” mix! End of challenge.

NO REAL CONTEST

Not only has the State Highway Administration been able to remove U.S. Route 40 and Maryland 213 from its list of “Trouble Spots”, but they’ve also saved approximately $90,000 in bi-annual maintenance costs. With the HMA section deforming less than three tenths of an inch during the past six years of ever increasing traffic loads, the results of the “contest” between Hot Mix Asphalt and Portland Cement Concrete have proven to be “no contest” at all.