26 February 2016 • ROADS&BRIDGES

Blue-tiful

Remote, mountainous location 

recycles in place with great results

T

he Blue Ridge Parkway is a scenic 

highway set high in the mountains 

of Virginia and North Carolina.

By Brian W. Budzynski

Managing Editor

Unlike a standard highway that is optimized to carry the maximum number of vehicles from here to there, directly as possible 

and at high speeds, the Parkway was designed 

to showcase the beauty of its surroundings. 

Consequently, it has many sharp turns and 

steep grades along a meandering route that 

offers beautiful vistas across some pretty 

tough terrain. Both the road and surrounding 

land are owned and managed by the National 

Park Service (NPS) and limited access points 

are provided from “normal” roads. The NPS 

goes to great lengths to keep the environment surrounding the highway pristine and 

undisturbed. One might, therefore, appreciate 

the challenges a construction contractor 

would face in the process of rehabilitating this 

unique roadway—both in terms of appeasing 

the stakeholder and respecting the nativity 

of the site’s environs. Moreover, employing 

an aspect of environmental stewardship in 

the construction process itself presented its 

own particular challenges. The success of the 

Blue Ridge Parkway Pavement Rehabilitation Project was no small feat; as such it 

is the recipient of a 2016 ROADS & BRIDGES/

Asphalt Recycling and Reclaiming Association 

Recycling Award.

Normal vs. Parkway

“In a normal full-depth reclamation (FDR) 

project using portland cement, staging areas 

are arranged along the project site to transfer 

cement from tanker trucks to spreaders,” Stan 

RECYCLING

ARRA

AWARDS

2016
28 February 2016 • ROADS&BRIDGES

Bland, pavement applications director for 

the Portland Cement Association’s Southeast 

region, told ROADS & BRIDGES. “The spreaders 

lay the cement on the pulverized pavement 

prior to mixing and compaction. However, 

because of the special nature of the surrounding land [on this project], the spreaders had 

to be filled miles away at the bottom of the 

mountain, along a narrow, steep and curving 

road. Consequently, careful planning was 

needed to make sure the process was consistently supplied with cement and great care 

was taken to ensure that virtually no cement 

escaped the roadway.”

There’s remote and then there’s remote. 

The Parkway qualifies as the latter. As contractor Slurry Pavers’ head of business development for reclaiming and stabilization David 

Stowell told ROADS & BRIDGES, “Keep in mind, 

this road is built on the spine of a mountain.” 

As a solely recreational throughway, the 

road does not allow truck traffic. And while 

a typical highway will experience its highest 

traffic volumes during the work week, traffic 

on the Parkway peaks on the weekends, when 

recreational users are numerous. Thus, before 

even getting in to assess the situation and get 

down to work, crews had a time stricture on 

their hands.

“Work was allowed during the week,” 

Bland said, “but the Parkway had to be fully 

open and ready for tourists on weekends.” 

A point which Stowell quickly confirmed. 

“Weather was no excuse,” he said. “In order 

to accommodate visitors to the park, we had 

to have all reclamation and paving done 

by Friday afternoon, and if the forecast did 

not look favorable, we had to take that into 

account along the work week.”

Testing to know

According to Bland, prior to FDR with 

portland cement, the road is sampled to the 

planned depth of reclamation. The recovered 

material may include existing hot-mix asphalt, 

unbound granular base and subgrade. The 

mixture is taken to a testing laboratory and 

any large pieces are pulverized to represent 

the situation expected on the roadway. 

This mixture is then tested for optimum 

moisture content and maximum dry density. 

Once those factors are determined, a range of 

cement contents are compacted at optimum 

moisture to maximum density and moist 

cured for a week. These samples are tested 

for compressive strength and the spread rate 

of cement is determined from the results. 

The selected cement content was based on 

achieving a seven-day compressive strength 

of approximately 400 psi. (The executive 

summary from Slurry Pavers called for a 

range of 300-500 psi.) Too much cement can 

result in undesirable cracking due to excessive 

shrinkage, so, in “Goldilocks” manner, it is 

necessary to select a cement content that is 

neither too high nor too low.

Cement content and target moisture 

and compaction values were then based 

on the laboratory testing. Of course, these 

values varied along the project, dependent 

on the variation in soil types and pavement condition.

“We were able to maintain 8 in. throughout 

the project,” Stowell said. “However, there 

were some variances in material. Some of the 

sections we found ‘boney’ [larger aggregate 

with little fines], down to almost a small fine 

stone, down to a red clay. Topography played a 

role in the variances. There were also a variety 

of materials used in the original road construction due to availability, location and logistics.” 

“All man-made items vary,” Bland said. “It 

just depends on the precision of the measurement as to whether it is detectable. All base on 

this project was within the specified tolerance.”

The process

The quality control on the Parkway project 

was typical of FDR with portland cement. The 

cement spreader was frequently calibrated 

during the day using a sq-yd-size tarp to 

capture and weigh the cement being spread 

per sq yd. The depth of the mixing was likewise checked regularly. In particular, proper 

compaction is key to obtaining strength from 

FDR with portland cement. Accordingly, 

compaction was monitored closely using a 

nuclear density gauge to ensure appropriate 

strength and double-checked with compressive strength testing of cores. Also, the 

cross-slope and grade of the compacted base 

were monitored to ensure a smooth ride in 

the finished product.

“The reclamation process was done 

entirely in place,” said Bland. “The existing asphalt pavement and stone base were 

completely mixed and incorporated into the 

new, stronger base right there.”

A 4,000-gal Kenworth water tanker makes its way down the Parkway trailed behind by a reclaimer. 
30 February 2016 • ROADS&BRIDGES

The existing pavement was pulverized to 

the specified depth of 8 in. using a Wirtgen 

WR2500S reclaimer, typically for a distance 

of approximately 600-800 ft. Behind the 

reclaimer, a Deere 672G motor grader roughly 

shaped the pulverized base and made a small 

windrow on either side of the lane to hem in 

the raw cement during mixing. Once the pavement was pulverized and shaped, calibrated 

Kenworth cement spreaders went to work 

applying portland cement (with an allowable 

variance of 5% off testing rate). A Kenworth 

4,000-gal water tanker was attached to the 

reclaimer and made a second pass to mix 

the pulverized pavement and cement, which 

was brought in from the mixing area at the 

foot of the mountain in a LBT Bulk Taker, or 

“Pig.” During this second pass, the reclaimer 

injected water at a controlled rate during the 

mixing to bring the final mixture to within 

2% of optimum.

Once more, the mixture was roughly 

shaped with the 672G motor grader and 

compacted in a 1-2-3 pattern that employed 

a Hamm 3412P combination roller until 

the mixed base “walked out.” The Deere 

motor grader was then used to strike off the 

base and the surface was finished with a 

Hamm HD+120VP steel double-drum roller. 

Compaction testing was performed with a 

nuclear density gauge, and once compaction 

targets were verified, the reclaimed pavement was moist-cured overnight. Traffic was 

maintained on the completed FDR until 

the following morning, when the reclaimed 

road received its first layer of asphalt 

concrete surface. 

Due to the weekday-only schedule as well 

as weather issues that can occur suddenly in a 

mountain climate, it was slow going.

“Typical productivity for this type of operation is approximately a 1⁄2 lane-mile per day,” 

said Bland. “However, the paving restraints on 

this project only allowed FDR work Monday 

through Thursday at noon. All FDR had to be 

surfaced with the first asphalt layer the following day. All operations then stopped for the 

weekend. So, the contractor could complete 

only 1⁄4 to 1⁄2 mile of paving per week.”

Pressing on

“Logistics . . . the great obstacle,” Stowell 

said. “We were not allowed to stage on the 

Parkway, so we staged at the bottom of the 

mountain, 20 miles from the construction 

site. The nearest water source was a stream 23 

miles away, so water had to be [siphoned] and 

hauled to the top of the mountain. During 

this time we had to satisfy the Department 

of Environmental Quality (DEQ) requirements. All cement was delivered, stored, and 

pulled from the same location, at the bottom 

of the mountain, also maintaining DEQ 

requirements. And the weather . . . well, it 

could be sunny in the valley but raining at the 

top of the mountain at the jobsite. You might 

have a perfectly sunny day and a dense fog 

would arrive and [force you] to halt operations. Every day was a new event.”

Coupled with spotty cell coverage and 

limited handheld radio dependability, crews 

pretty much had to make due with a tough 

situation for which there was no ready solution except to keep pressing on.

And so they did, and when all was said and 

done, the 12-mile, multi-county Blue Ridge 

Parkway Rehabilitation Project was completed 

in just under five months at a cost savings of 

approximately $2.65 million—all while curbing 

the environmental impact of the average road 

rehab project and revitalizing a crucial artery to 

some of Virginia’s most captivating landscape 

for, hopefully, another generation. R&B

For more information about this topic, check out 

the Asphalt Channel at www.roadsbridges.com.

Left: Part of freshly surfaced 1⁄2 lane-mile.

Below: A Deere 672G motor grader milled 

the base of the roadway.