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The Road
Recycled
F U L L - D E P T H R E C L A M A T I O N W I T H C E M E N T
Reuse existing materials on site
Extend pavement life with a stronger base
Save natural resources and money
Recycling Renaissance:
FDR with Cement
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P o r t l a n d C e m e n t A s s o c i a t i o n
Roads are a national resource. Roads have made it pos-sible for this country to reach social, economic and mil-
itary sophistication. Its important that we do all we
can to preserve them, maintain them, update them and rehabilitate them
as needed. The reauthorization of TEA-21 will have an impact on
what the future holds for this precious resource but even at the high-
est conceivable level of passage there will always be the need to
stretch the dollars as far as possible.
Typically when we think of roads, we think of the Interstate system
and urban traffic congestion. We often forget about the thousands of
miles of rural, farm-to-market roads, secondary roads and service
roads that are just as important to the overall function of our road sys-
tem. These too must be maintained and updated. While there are
any number of approaches to road reconstruction, In-Place Full-Depth
Reclamation or Recycling with cement offers everyone a win-win sit-
uation: its cost effective and stretches tax dollars; it can be done in
a relatively short time frame; with cement, its durable and long last-
ing. This process rebuilds worn out asphalt pavements by recycling the
existing roadway. The old asphalt and base materials are pulverized,
mixed with cement and water, and compacted to produce a strong,durable base for either an asphalt or concrete surface. Since the old
material is being used, it doesnt have to be hauled away, and new mate-
rial doesnt have to be brought in.
A surface consisting of a thin bituminous chip seal, hot-mix asphalt,
or concrete completes the road. The recycled base will be stronger, more
uniform, and more moisture resistant than the original base, resulting
in a long, low-maintenance life. The most important factor is that
recycling costs are normally at least 25 percent to 50 percent less than
the removal and replacement of the old pavement.
Conserving virgin construction materials through recycling with
cement makes smart economic and strategic sense. Our aggressive coast-
to-coast growth over the last century has seriously depleted once
plentiful aggregate supplies. Unless youre in the business, you never
realize how expensive rocks are. In many areas aggregates either come
from distant quarries at great expense or from local sources offering
only marginal quality. Continuing to exhaust these valuable resources
to rebuild existing roads only exacerbates the problem.
If the old asphalt and base materials are not recycled, they must
be disposed of or stockpiled, increasing transportation costs and
using valuable landfill space. In some regions, old asphalt can no longer
be land filled. Environmental laws are becoming strict, adding to the
expense of mining new materials and disposing of the old.
Recycling old roads with cement makes them a renewable resource.
The original investment in virgin road materials becomes a one-
time cost, which is renewed through cement stabilization and addition
of a new, thin surface course. Stabilizing the old road, its asphalt
surface, granular base, and underlying sub grade soil with cement, cre-
ates a strong pavement foundation.
The basic procedure is simple. The complete recycling process can be
finished in one day, and local traffic flow restored almost immediately.
How Do You Do It?
The procedure includes the following steps:
Thickness Design Pavement thickness can be determined by
using PCAs Thickness Design for Soil-Cement Pavements (EB068).
Other methods, such as the American Association of State Highway
Fu l l -Depth Rec lamat ion With
Cement
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P o r t l a n d C e m e n t A s s o c i a t i o n
and Transportation Officials (AASHTO) Guide for Design of Pavement
Structures can also be used.
Site Investigation The site should be investigated to determinethe cause of failure. Cores or test holes should be used to determine
layer thicknesses and to obtain samples of the material to be recy-
cled (which can include asphalt surface, base course aggregate,
and subgrade).
Lab Evaluation Material samples from the site should be pulver-
ized in the lab to create an aggregate-soil mix that will be similar to
that expected from the recycling process. The mix design procedure is
the same as that performed for soil-cement. Refer to PCA publication
EB052, Soil-Cement Laboratory Handbook. This includes the determi-
nation of maximum dry density and optimum moisture content. If
unconfined compressive strength is used to determine cement content,
a 7-day strength of 300 to 400 psi is recommended.
Pulverization The first step in construction is to pulverize the road-
way with a machine similar to a giant roto-tiller. It pulverizes and
blends the asphalt surface with the base. There are several manufacturers
that produce machines especially designed for quality full-depth recla-
mation. Pulverization is usually 6 to 12 inches deep, which on secondary
roads will typically include all of the surface and base, plus some
part of the subgrade. To achieve the proper gradation after pulveriza-
tion, more than one pass of the equipment may be necessary. The par-
ticle distribution should have 100 percent smaller than 2 inches (50 mm)and 55 percent passing a No. 4 (6-mm) sieve.
Shaping And Grading The
pulverized material is shaped
to the desired cross-section
and grade. This could involve
additional earthwork in order to
widen the roadway. Final base
elevation requirements may
necessitate a small amount of
material removal or addition.
Spreading Cement Cement
is spread in a measured
amount on the surface of the
shaped roadway, in either dry
or slurry form.
Water Application Wateris added to bring the aggre-
gate-soil mixture to optimum moisture content (water content at max-
imum dry density as determined by ASTM D558), either in front of the
pulverizer/ reclaimer or in the mixing chamber.
Mixing The aggregate-soil-cement-water mixture is combined and
blended with the pulverizing/ reclaimer machinery. Depending on the
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Write In 136 - Or Reply Online
Full-Depth Reclamation
with cement, or FDR,
uses old asphalt and
underlying base
material to build a
new road. Existing
pavement is pulverized,
mixed with cement and
water, and compacted
to produce a strong,
durable base for
either an asphalt or
concrete surface.
Existing materials are
recycled on site. Theres no
need to haul in new aggregate
or haul out old materials for
disposal. FDR conserves
natural resources, saves
energy, and reduces waste.
A stronger base means
longer life. Stronger than
an unstabilized base, acement-stabilized base
FDR is an economically
and environmentally
sound decision
0022-03-343
keeps water out and standsup to heavy, constantlyincreasing traffic loads,reducing maintenance andprolonging pavement life.
Recycling saves money.FDR with cement costs up to
50% less than removal and
replacementof old pavement
or thick overlays.
To find out more, visit our Web site at
www.cement.org/FDR
Recycle Failed Pavement withCement
Recycle Failed Pavement withCement
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There are many opportunities to gain from the environmental
and economic advantages of Full Depth Reclamation (FDR) with
cement. Although the most obvious applications are rural roads,
virtually any paved surface in need of rejuvenation, especially if there
are indications of base problems, is worth consideration.
Essentially what has to happen is the old pavement has to be pul-
verized, in place and then mixed with the original base materials.
Cement is spread across the surface either as a dry material or
slurry mix. Water is added. The ingredients are mixed in place and
the material compacted and then allowed to cure before the finish
surface is applied.
The end-result quality depends on:
The pulverization
(100 percent smaller than 2 inches)
The cement content
The moisture content
The mixing
The density The curing
Milling machines and reclaimers are not the same machine. Prob-
ably the most significant difference is that milling machines discharge
the removed road materials while reclaimers retain these materials in
a mixing chamber and discharge them back onto the roadbed from which
they were removed.
The basic makeup of a reclaimer includes: the drive unit and the
milling/mixing unit; operators station; rotor; mixing chamber; water tanks;
chassis or frame; drive axles and steering axles; brakes; a host of
sophisticated electronics and multiple hydraulic systems. Typical
options include items like working light packages; four-wheel drive (if
this is not a standard feature); water spray systems; emulsion systems
and other interesting goodies designed to make the operator more
comfortable and more productive.
In the U.S. there are four manufacturers producing and distributing
reclaimers: Bomag, Caterpillar, CMI and Wirtgen. These machines
are designed, engineered and manufactured to handle FDR projects effec-
tively and efficiently.
Bomags offerings include the MPH 122 Stabilizer/Recycler; the MPH
362/364-R/S/SDM Recycler, Stabilizer, Stabilizer Deep Mix; and the MPH
454 R/S Recycler/Stabilizer. All the machines feature hydrostatic
drive. All wheel drive is standard on all of the machines except the MPH
364 that has a front wheel drive option.
The operators station is designed to be comfortable and ergonom-
ically friendly giving the operator good visibility and easy-to-use
controls. The equipment is designed for easy maintenance with
major components positioned for easy access and service. Accord-
ing to Bomag the cutting teeth are quick and easy to replace. The rotor
end segments are bolted on and in case of excess wear, can be
replaced without removing the rotor.
On the 362/364 models there is a selectable 2-speed rotor design to
give the operator better control over production volume. The 454 features
a selectable 3-speed rotor, and on the 122 the rotor is a variable speed
unit. Four-wheel drive and steer are standard features on these machines.
8
P o r t l a n d C e m e n t A s s o c i a t i o n
Bomag MPH 122 MPH362/364 R/S/SD MPH 454 R/S
Operating Wt. 45,636 lbs 39,000 lbs. 46,300 lbs.
Engine horsepower 442 360 450
Working speed 211 fpm 187 fpm 221 fpm
Rotor configuration Center slung Rear slung Rear slung
Rotor Drive Hydrostatic Hydrostatic Hydrostatic
Rotor Width 91.7 in. 79 in. 96 in.
Outside diameter 48.2 in. 44/48/59.5 in. 48 in.Max cutting depth 19.7 in. 12/14/21 in. 15 in.
Number of teeth 194 168/70/70 196/82
Cutter direction Upward Upward Upward
Cutter speeds 2 2 3
Equipment For
Fu l l -Depth Rec lamat ion/Recyc l ing
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Caterpillar has two models, the RM-250C and the RM-350B.
Both machines can be converted from a reclaimer configuration to a
mixer or stabilizer on the job. On the 250C you have 3 rotor options,
breakaway reclamation, quick-change stabilization and combinationrotors. The teeth in the breakaway and combination rotors can be
replaced without welding.
Both of the Cat machines use mechanical drives to operate the rotors.
On the 250 a direct mechanical drive transfers engine power to the
rotor and has 3 operating speeds to better match the materials being
reclaimed and the depth of the cuts. A heavy-duty shear disc or
optional torque limited protects the rotor drive
components from torsional stress and shocks.
Drive chains, rated at 135,000 pounds, are
located on both ends of the rotor. On the 350B
the rotor drive is the same except that a Cat
powershift transmission is used to transfer
engine power to the rotor.
On both models the rotor and mixing cham-
ber are mid-mounted to take advantage of the
machines weight. They come standard with an open operators station,
and a ROPS and cab option.
The 250C is front wheel driven but there is a rear wheel assist
option that increases the tractive effort by 22 percent in first gear,
34 percent in second and 64 percent in fourth. The bigger 350B is
an all-wheel drive unit.
Depth of cut can be controlled manually or automatically with an actu-
al rotor height displayed on machines dashboard. Sophisticated elec-tronics and state-of-the-art hydraulics are designed to minimize operator
fatigue and frustration. Four-wheel drive and steer are standard.
CMI Terex has five models available. They manufacture a wide range
of cutters to expand the application possibilities for these machines.
The RS 325 is the only one of the lineup that has a rear slung rotor.
The other models are center mount. 4-wheel drive is standard on all
models. All models come with 4-wheel steer as standard with vari-
ous steering configurations from which the operator can select.
On the 500C, 650B and 800 models a microprocessor based con-
trol system automatically maintains cutting depth, cross slope and
travel speed. An engine load sensing system automatically adjusts
travel speed to cutting conditions. LCD readout provides the oper-
ator with continuous display of machine functions.
Options, depending on the model include a larger cutter mandrel that
increases the cutting depth to 20 inches; ROPS; water spray systems,
asphalt distribution systems and a Kennametal change random pattern
cutter mandrel.
9
P o r t l a n d C e m e n t A s s o c i a t i o n
CMI Terex RS-325 RS-425 RS-500C RS-650B RS-800
Operating weight 31,200 lbs. 49,000 lbs. 60,460 lbs. 63,500 lbs. 67,500 lbs.
Working speed 200/360 fpm 175 fpm 210 fpm 210 fpm 210 fpm
Horsepower 330 425 525 650 800
Rotor Configuration Read slung Center Center Center Center
Rotor drive Mechanical Mechanical Mechanical Mechanical Mechanical
Rotor width 75 in. 96 in. 96 in. 96 in. 96 in.
Rotor diameter 50 in. 50 in. 50 in. 50 in. 50 in.
Cutting depth 16 in. * 16 in. 16 in. 16 in. 16 in.
Number of teeth 223 218 218 218
Cutter direction Upward Upward Bi-directional Bi-directional Bi-directional
Cutter speeds 2 3 4 4 4
Caterpillar RM-250C RM-350B
Operating weight 35,635 - 37,000 lbs. 48,270 - 53,680 lbs.
Engine horsepower 335 500
Rotor Configuration Breakaway/combination/ Breakaway/combination/
stabilizer stabilizer
Rotor Drive Mechanical Mechanical
Rotor width 96 in. 96 /90 in.
Outside Diameter 45/48/54 in. 52/54/58 in.
Cutting depth 13/15/18 in. 15/16/20 in.
Number of teeth 180/108/58 188/200/58
Cutting direction Reclaimer - upcut Reclaimer -upcut
Stabilizer --downcut
Cutter speeds 2 3
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According to the manufacturer, the mechanical rotor drive system
increases productivity. On the 3 larger machines elevation control is
manual or automatic with individual controls for the left front, left rear
and right side. An optional cross slope control is available.
Wirtgen has two models the WR 2500 S and the WR 2500 SK. The
2500 S has a wide cutter option available. One of the features is the
volume of the mixing chamber adjusts automatically according to the
amount of material being processed. The manufacturer describes the
operation station as a fun place to work. The operator can run the
machine from an optional fully enclosed cab.
All machine functions are activated through microprocessors. The
operator has access to critical operating information with Wirtgens Con-
trol Graphic Center (CGC), which lets him monitor any and all functions
at any time. Milling depth is displayed on the CGC panel.
Automatic power control adjusts the feed rate as a function of the
engine load. The operator can deactivate the system and control the
feed manually.
Tool change is quick and easy. An optional hydraulically driven
drum turning attachment makes it easier to rotate the drum while
changing tools.
The Wirtgen machines feature 4-wheeld drive and 4-wheel steer as
standard. The manufacturer has a variety of options that make it pos-
sible for machine owners to fit the machine to their application needs.
As noted, there are other ways of doing FDR but none are as effi-
cient as using a machine specifically designed for this application. The
combination of these machines and the economic benefits offered
by FDR make it possible to stretch highway dollars for miles.
10
P o r t l a n d C e m e n t A s s o c i a t i o n
Wirtgen WR 2500 S (std.) WR 2500 (opt.) WR 2500 SK
Operating weight 72,600 lbs. 75,460 lbs. 82,720 lbs.
Working speed 49.2 to 655 fpm 49.2 to 655 fpm 49.2 to 655 fpm
Horsepower 670 670 670
Rotor configuration Center Center CenterRotor drive Mechanical Mechanical Mechanical
Rotor width 97.5 in. 121.9 in. 97.5 in.
Rotor diameter 59.2 in. 59.2 in. 59.2 in.
Cutting depth 20 in. 20 in. 20 in.
Number of teeth 224 224 224
Cutter direction Bi-directional Bi-directional Bi-directional
Cutter speeds 4 4 4
A good foundation is important for any structure, especiallypavements. The pavement base provides the thickness andstiffness necessary to carry heavy traffic loads.
Stabilized pavement bases, such as soil-cement and cement-treat-ed base have provided economical, long-lasting pavement foundationsfor over 60 years. These pavements combine soil and/or aggregatewith cement and water, which are then compacted to high density.
The advantages of stabilization are many:Cement stabilization increases the stiffness and strength of the base
material. A stiffer base reduces deflections due to traffic loads,which results in lower strains in the asphalt surface. This delaysthe onset of surface distress, such as fatigue cracking, and extendspavement life.
The strong uniform support provided by cement stabilization resultsin reduced stresses applied to the subgrade. A thinner cement-sta-bilized section can reduce subgrade stresses more than a thicker layerof untreated aggregate base. Subgrade failures, potholes, and roadroughness are thus reduced.
Moisture intrusion is the nemesis of pavement bases. Cement-sta-bilized pavements form a moisture-resistant base that keeps waterout and maintains higher levels of strength, even when saturated.
A cement-stabilized base also reduces the potential for pumpingof subgrade fines.
Start With A Good Foundation
A stabilized base spreads loads and
reduces stress on the subgrade.
Unstabilized Granular Base Cement-Stabilized Base
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In recent years, the highway industry throughout the
United States has become increasingly concerned
about extensively deteriorated and under-designed
pavements. Many of these pavements have long passed the
time for which they can be effectively patched or spot
repaired in order to accommodate an economically feasible
or effective overlay. Cold, in-place full depth recycling is
proving to be a solution to these problems.
South Carolina Route 97 in York County had been an
extreme and constant maintenance problem for many years.
This section of distressed pavement stretches from the
Chester County line north to Hickory Grove, a distance of approxi-mately 16 miles.
Originally constructed in the 1930s as secondary roads 33 and 39, Route
97 was first improved in 1948 as SC Route 907 and Road 39 by Dicker-
son Incorporated, of North Carolina, for a cost of $144,055. In 1975
another 10-mile section of the highway was reconstructed.
Shortly after the completion of this road, slips and other forms of
pavement stress began to appear. The department investigated these
problems in depth, but no definitive answers could be reached.In 1983, after years of problems, the department let a resurfacing
contract to overlay the worst sections. Once again problems sur-
faced as slips and failures began to occur. None of these occur-
rences could be directly tied to the asphalt mix since it met all
department requirements, and no problems had been noted at the plant
or in the lay-down process.
For the next 12 years, this highway deteriorated rapidly and required
weekly maintenance. The work consisted of failure repair
through partial or full-depth patching. In areas where con-
stant problems kept reoccurring, the DOT had to remove and
replace extreme depths with asphalt. These costs amount-
ed to approximately $34,500 per year.
In addition to these routine maintenance procedures, the
department scheduled full depth repair using a Bomag on
some occasions, trying to better and more permanently repair
11
P o r t l a n d C e m e n t A s s o c i a t i o n
Rehabi l i ta t ing
Above: A view of a deteriorated roadway prior to rehabilitation.
Left: The finished roadway prior to the application of the asphalt con-
crete binder course and surface course.
Route 97Cold, in-place full depth recyclingis proving to be an effectivesolution for damaged roads.By Frank S. Bland Jr., P.E., District Four Construction Engineer,
South Carolina Department of Highways. Edited by Christina
Fisher. Pictures courtesy of Site-Prep, Inc. of N.C.
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areas where standard methods
just did not do the job. These
repairs created additionalexpenses amounting to
$25,000 over five years.
To free the maintenance
unit of this constant respon-
sibility, the department decid-
ed to let this section of
roadway to contract. The main concern was finding the best method
of repairing the existing pavement and applying a suitable overlay that
would be maintenance free and provide the public a uniform section
of pavement for which they had so patiently waited.
Because the condition of the pavement was so poor, it was decid-
ed that the most effective way to rehabilitate the road would be to use
in-place recycling by incorporating cement
into the top 6 inches of the pavement
and base/sub-base to create a stable
foundation upon which the remainder of
the pavement structure could be placed.
Cold, in-place full depth recycling,
or reclaiming of flexible pavement, is arehabilitation technique in which the
existing bituminous surface and part or
all of the underlying base
and/or sub-base materials
are pulverized in place to a
specified particle size range
and mixed cold with either
standard or non-standard
additives to form a new sta-
bilized base course.
In order to meet the
design criteria, the top 6
inches of cement modified
base was followed by the
placement of a type A single
treatment. This treatment
would act as a seal to hold
in the moisture and provide a temporary surface on which traffic
could continue to move. This would then be overlaid with 225 pounds
of asphalt concrete binder
course and 175 pounds of
asphalt concrete surfacecourse.
Once the department decid-
ed upon this method of con-
struction, the contract and
special provisions for this new
venture were developed,
although the department had limited knowledge and no practical
experience in this relatively new technique. The prices had to be
assumed in order to come up with some estimated cost. Therefore, it
was determined that the department would let the contract for only a
10-mile portion of the road. The remaining six miles would be added
if the contract amount was less than the estimate cost but in an
amount great enough to cover
the additional length.
Sloan Construction Compa-
ny of Greenville, South Car-
olina, won the contract with a
bid of $1,611,538, which
allowed for the completion ofthe additional six miles. Sloan
Construction subcontracted
the base work to Base Con-
struction Company, Inc, Colum-
bus, Ohio, which specializes
in this type of construction.
Base Construction representatives
explained the process and discussed
any problems that could be encountered
during the project.
The prime contractors plans were
to begin placing the surface treatment
approximately three days behind the
stabilization procedure. Two days after
this, the placement of binder would
follow and continue until the entire
roadway had been overlaid. The final
riding surface placement would begin if time and weather permitted.
Since this work was beginning in a traditionally poor time of year for
12
P o r t l a n d C e m e n t A s s o c i a t i o n
Various rollers and compaction equipment are then used on the new road bed toachieve the correct density.
It would have cost the department
$1,637,375 to prepare the base for theasphalt layers. The price to stabilize the entire
length of the project was $513,480.
This amounted to a savings of 69 percent.
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construction, weather would play a major role in how far
we could go.
Base Construction moved onto the job and began workon November 13, 1995. Progress was slow at first as the
contractor and department personnel began to get a feel
for the types of materials onsite and how they compared
with jobs already completed in other areas of the country.
During this learning phase, Hamm Corporation sent their
specialist, Ace Wise, to our location to share his expertise
with the department.
It was decided that the temperature restrictions for
soil cement could be relaxed somewhat due to the ground
temperature in this region and the heat of hydration from
the process. Looking at results from other areas of the coun-
try, it was decided that we could begin work at 25 degrees
Fahrenheit and rising as long as we anticipated temperatures to get
above 35 degrees during the day.
Due to the near 100 percent compaction effort, the department
determined that light passenger vehicles could immediately use the road
with no damage. The road was detoured for all vehicles with six tires
or larger in an effort to protect the treated area from extreme and dam-
aging loads.With the wide variation in pavement thickness and the need to run
with some consistency to create a continuous beam effect, the con-
tractor asked that the department consider placing a 9-inch stabilized
depth in all areas to avoid jumping back and forth from 6-inch to 9-
inch depths. This would create consistency with only a few areas need-
ing 12-inch treatment.
To begin the stabilization procedure, cement tankers placed raw
cement onto one lane of Route 97 to create a 6 percent addition. This
cement was then blended into the structure with two overlapping pass-
es of a Hamm RACO 250 soil stabilizer-asphalt/recycler. The properamount of water was added by the equipments spray system, which
has the capability to meter out the exact amount specified to achieve
maximum compaction.
Productivity, which was measured by the number of feet per
mile, varied as the machine encountered pavement of varying
thicknesses and composition. However, on an average, the
machine traveled at a speed of 30 feet/minute under ideal con-
ditions. We placed a maximum of 10 tankers of cement in a
one-day period. However, on the average, we placed between
five and six tankers per day. This would amount to stabilizing
a 12-foot lane for a distance of approximately 3,500 feet, or
approximately 5,000 square yards of stabilization.
Once the machine had completed its passes, the spreading
and shaping operation began using a motorgrader. As a part
of this spreading operation, the mixture was shaped so that
13
P o r t l a n d C e m e n t A s s o c i a t i o n
Above: Water is added during the blending process and while the newroad bed cures.
Left: A layer of cement is placed on the roads surface to be blended with
the pulverized road bed with the asphalt/recycler.
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when compacted it was within close conformity with the lines, grades
and cross-sections that originally existed.
The compaction and finish grading came next. The mixture should becompacted when it will bear the weight of the roller or compactor
without undue displacement, cracking or shoving of the premixed
materials. A suitably sized, single drum vibratory padfoot compactor nor-
mally achieves initial density of the loose, newly reclaimed base course.
On our project the initial and final density was accomplished using a Hamm
2520 vibratory padfoot roller.
The Hamm GRW 5 pneumatic roller then finished rolling the area to
mechanically seal the surface and to complete our compaction process.
It also served as a proof roller for the area and indicat-
ed any possible soft spots. The new base was com-
pacted to an average density of 98 percent of standard
proctor density.
The area was allowed to cure under light traffic (pas-
senger vehicles) by maintaining a water type curing
process for three days, which was then followed by the
placement of bituminous surfacing single treatment.
This sealed the road and minimized damage, allowing light
traffic to continue to travel the area. All heavy loads
were detoured.The cold, in-place, full depth flexible pavement recy-
cling was completed and the remainder of the work
was no more than a resurfacing project. This amounted
to the placement of 225 pounds per square yard of an
asphalt concrete binder course and 175 pounds per square yard of
asphalt concrete surface course.
There are many advantages and benefits to this process, and some
of these include:
All work takes place on the
existing pavement section.
Full-depth reclamation resulting
in a stable base at significant savings
over conventional methods.
Reuse of natural resources.
Ability to eliminate reflective cracking.
Improved resistance to water
penetration of the subgrade.
Adaptability to treat all types of
reflective pavement distress.
Minimal hauling costs, as the
procedure occurs in place.
Traffic can be maintained duringthe reclamation proceedings.
Reclamation process is environmentally safe.
The speed of the operation allows for minimum
inconvenience to the public.
Provides good beam effect that distributes traffic load evenly
throughout pavement.
Asphalt rates can be reduced due to the increased strength
of the new base.
Using this process, we obtained a much-improved base at significant
savings. If this project had been let using conventional means of full depth
patching, it would have cost the department $1,637,375 to prepare the
base for the asphalt layers. The price to stabilize the entire length of the
project was $513,480. This amounted to a savings of 69 percent and
allowed us to complete an additional amount of mileage.
As we neared the end of the project, cores and follow-up testing deter-
mined what structural number we attained and what the actual truck
carrying capacity was. These tests will mean better and more realis-
tic designs in the future.
We will continue to study this project to be better able to evaluate
cold, in-place, full depth flexible pavement reclamation. However, from
visual observation and the growing number of states beginning to
use this process, we feel it is definitely a viable technique to rehabilitate
roads that have extensive failures and base problems.
14
P o r t l a n d C e m e n t A s s o c i a t i o n
Once the new base material has been blended, spreading and shaping can begin with a motorgrader.
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type of mixing equipment, uniform blending of materials can usually
be achieved in one pass of the mixer.
Compaction Although requirements vary, the mixture is compact-
ed to a minimum density of 96 percent to 98 percent of standard
Proctor density (ASTM D558). The compaction is usually performed with
smooth-wheeled or sheeps-foot vibratory rollers. A pneumatic-tired roller
may follow to finish the surface. Final compaction should take placeno more than 3 hours past initial mixing of the cement. The field den-
sity and moisture are monitored for quality control purposes.
Curing On light-traffic roads, the compacted base can
accept traffic almost immediately after construction. For prop-
er hydration, the soil cement is kept moist by periodical-
ly applying water to the surface. Curing begins immediately after final
compaction and is continued for several days. The application of the prime
coat should occur as soon as possible to ensure that moisture is sealed
inside the base.
Pavement Surface The new pavement surface consisting of a
chip seal, hot-mix asphalt, or concrete is constructed to complete the
recycling process.
Quality Control Recycling with cement follows the same basic pro-
cedures used for normal soil-cement operations. The
success of a recycling project depends upon the care-
ful attention to the following control factors:
Adequate pulverization
Proper cement content
Proper moisture content
Adequate density
Adequate curing
Traffic Control All operations can be performed
under normal construction traffic control. Disrup-
tive road closures are not required.
End Result A high-quality, long-lasting, inex-
pensive road that was reconditioned in a minimal
amount of time with a minimum degree of incon-
venience to its users.
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P o r t l a n d C e m e n t A s s o c i a t i o n
Savings in Energy Use
Full-Depth Recycling vs. New Base
Based on 1 mile of 24-foot-wide 2-lane road,
6-inch base and 2-inch asphalt surface
Number of trucks needed
New Roadway Material(tons)
Material Landfilled
(cu. yd.)
Disel Fuel Consumed
(gal.)
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P o r t l a n d C e m e n t A s s o c i a t i o n
When severe alligator cracking reared its ugly head
along a heavily trafficked truck route cutting
across North Texas, state engineers faced a chal-
lenge. Drop offs along the narrow, hilly two-lane US 79 highway
meant that building detours would be
expensive and impractical. We had
to keep traffic on it while we
strengthened it, says Mark Stur-
rock, assistant area engineer, Jack-
sonville area office, Texas Dept. of
Transportation.
So engineers decided to recycle the
roadway in-place, a process that
allows traffic to flow with construc-
tion underway. They tested lime and
cement to determine which materi-
al worked best, says Sturrock. Full-depth recycling with cement provedthe most efficient way to keep the road open and not double-handle
the material, he says.
In March 2002, crews from Madden Contracting Inc, Minden, La., began
the $7.4-million contract to rebuild an 11-mile stretch of US 79 west of
Jacksonville, Texas. It
was the Jacksonville
offices first full-depth
recycling (FDR) with
cement project.
Madden mixed the
existing asphalt and
base with more than
8,000 tons of cement,
or 4-percent cement
by dry weight, into
333,864 square yards of roadway to create a strong, long-lasting
base. Five inches of Type C asphalt topped the new road.
Finished last February, four months ahead of schedule, the project
was deemed a tremendous success, says Ken Smith, the state
inspector overseeing the project. With cement, you get a tremendous
amount of strength.
Initially though, Smith questioned whether the contractor could obtain
density after pulverizing the existing roadway, mixing in cement 13 inch-
es deep, and compacting in one lift. On the projects first day, DaveKirkland, Maddens project superintendent, used a nuclear density gauge
to show Smith that they were
meeting compaction require-
ments. We were hitting 98
percent density with no prob-
lems whatsoever, says Smith.
And the process is fast. Mad-
den crews processed 10 loads
of cement, or 260 tons, per day.
There really were no nega-
tives but the tempo was fast. It
kept us on our toes, says
Smith. Its simpler than fooling
with lime because you have to
cut lime twice, adds Madden.
The success of the FDR proj-
ect encouraged engineers to design a second one for US 79 now
underway east of Jacksonville. The 10-mile, $6.1-million project is slat-
ed for completion to finish next summer.
Cement St rengthens
US 79By Jeff Hawk
With cement, you get a tremendous amount of strength.Ken Smith, TxDOT inspector
On a completed stretch of US 79 outside New Summerfield, Texas, TxDOT inspector Ken Smith called his first recycling with cementproject a tremendous success.
TxDOT inspector Ken Smith digs up a section ofpulverized roadway to check its depth.
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Performing Full-Depth Reclamation (FDR) on failed asphalt
pavements makes simple sense. The existing in-place
materials are reclaimed instead of importing expensive
virgin aggregates. By building a new stabilized base you provide an
excellent foundation for future pavement performance.
The selection and use of the stabilizing agent to construct the new
stabilized base is not a simple matter. Selecting the wrong stabiliz-
ing agent can lead to expensive premature pavement failures and
early repairs. The most common stabilizing agents in use today for FDR
are: cement, lime, asphalt emulsion, and foamed asphalt. Calcium chlo-
ride is sometimes used to improve compaction and control dust, but
it does not add significant strength to the base.
When designed and built properly, cement will perform well under
almost all conditions. The other agents, however, are nowhere near
as versatile and projects must be carefully screened to see if the con-
ditions are right for their use.
When an existing road is being reclaimed, a high degree a mate-
rial variation will likely be encountered during construction. This is
why versatility in a stabilizing agent is important. Different locations
may have different subgrade and base materials. Another factor is
that different asphalt patches of varying depths and mix may have
been used over the years. The good news is that cement can be used
successfully with virtually all types of aggregate and soil types.
This is not true with other stabilizing agents.
Lime
Lime provides increased strength to compacted soil through a chem-
ical reaction with clay minerals. If these clay particles are not pres-
ent in the reclaimed pavement materials (or if fly-ash is not added to
provide the needed minerals), then no pozzolanic reaction can take place
to provide increased strength.
6
P o r t l a n d C e m e n t A s s o c i a t i o n
Stabilizing Pavements There s Nothi ng As Versat i le A s Cement
Bad road foundations always cause bad roads.
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P o r t l a n d C e m e n t A s s o c i a t i o n
Cement, in contrast, provides its own chemical reaction by reacting
with the water in the reclaimed pavement and providing high strength
through hydration. This reaction will take place regardless of thetype of aggregate or soil. In addition, if clay minerals are present, cement
will also provide the same pozzolanic reaction that lime does, creat-
ing even more long-term strength.
Asphalt Emulsion
Using an asphalt emulsion with the FDR
process leads to a complicated reaction with the
reclaimed asphalt. The emulsion will rejuve-
nate some (but not all) of the old asphalt
cement, leading to a possibility that more emul-
sion may be available than what is desired. If
too much emulsion is present, the mix becomes
too rich and will not compact or cure properly.
On the other hand, if theres too little emul-
sion the particles in the mix will not bond
together and raveling can occur.
In contrast, using cement as the stabilizing
agent simply treats the reclaimed asphalt as
black gravel, and no rejuvenationof the old asphalt cement occurs.
This leads to more uniform con-
struction and fewer surprises in the
field when different amounts of old
asphalt are encountered in the
reclaimed mix.
Foamed Asphalt
This FDR stabilizing agent is cre-
ated by mixing asphalt emulsion
under pressure with cold water,
which foams the asphalt before it is
mixed with the reclaimed materials.
This process is very sensitive to
the mix of reclaimed materials (pro-
portions of old asphalt, gravel, sand,
and fines). If the mixture is not
properly designed, or if conditions
change in the field, failure can occur.
As mentioned, cement is far more versatile and can perform well
under varying mixtures of reclaimed pavement materials. To build the
best product, a cement treated material needs to be properly designedand constructed, but the risks taken by a road agency are much less than
with using other stabilizing agents.
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