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Rubblizing to rehabilitate existing pavements

Rubblizing to rehabilitate existing pavements

By Travis Walbeck, P.E., NCAT and Robert Horan, P.E., Asphalt Institute

Freeway
businesses around the country face a challenge when trying to find a solution to
tackle deteriorated concrete pavements. A number of viable choices can be found for
sound rehabilitation methods that may end in asphalt pavements with
wonderful service life.

Eradicating
the previous concrete and replacing it with new portland cement concrete (PCC)
pavement is an expensive choice. Removing the concrete and developing a brand new
scorching combine asphalt (HMA) pavement is generally inexpensive, nevertheless it nonetheless incurs
the price of eradicating and losing the previous pavement. Overlaying the prevailing
concrete with HMA is comparatively cheap. Nevertheless, with this feature,
reflective cracking could be a maintenance drawback.

In states
where there are a big number of miles of deteriorated PCC pavements or
PCC composite pavements, engineers want options to these typical
strategies which are value efficient and have a proven monitor report of
engaging in a permanent repair. Many freeway businesses are discovering that
rubblization of the deteriorated concrete and overlaying with HMA is probably the most
effective remedy choice.

Rubblization
is the method of fracturing the worn-out concrete into small, sometimes 2- to
6-inch, items and converting it into an interlocked however flexible base materials.
The rubblizing process breaks the bonds between any reinforcing metal and the
concrete, eliminates slab movement, and almost eliminates the potential for
reflective cracking. The process consists of “rubblizing” the concrete pavement,
then compacting and solidifying the roadbed earlier than resurfacing. This course of
will improve the lifespan of any overlay and guarantee a greater driving
experience for the traveling public.

Travis
Walbeck, former State Pavement Engineer for West Virginia Division of Highways
(WVDOH), said: “The choice was made to rehabilitate a large amount of
badly distressed composite pavements. A number of methods of reconstruction have been
thought-about and after a cautious analysis of all the choices, it was
decided that rubblization of the prevailing concrete pavement was probably the most
cost-effective choice.”

Historical past of rubblization in West Virginia

There is a
lengthy history of successful use of rubblization know-how on the West Virginia
Turnpike on I-64 and elsewhere in the state.

In June
1998, over 90 DOT employees from 15 states attended a rubblizing demonstration of a
16-year-old concrete pavement prior to putting a 10-inch thick HMA overlay on a
part of I-77 / I-64 on the WV Turnpike.

West
Virginia Turnpike officers gave quite a few reasons for choosing rubblization
as the perfect technique of rehabilitation. A number of the elements that have been thought-about
have been:

• A
10-mile part of the West Virginia Turnpike was rubblized in 1989 and
overlaid with asphalt. Its performance has been excellent.

• Complete
development with PCC is out of the question because it is too expensive and
time consuming.

• Delays
with heavy visitors circulate on the turnpike can be intolerable to the general public.

• PCC slab
repair and patching are costly and time-consuming. Visitors circulate is troublesome
during development. PCC patches don’t handle all the distresses in the
pavement.

• HMA
overlays without rubblization won’t forestall joints and cracks from
reflecting via in a relatively brief time.


Rubblizing has confirmed far cheaper than another PCC pavement
rehabilitation technique.

A restricted
rubblization program was carried out a number of years after the turnpike venture.
These tasks have not shown the same good performance because the absolutely rubblized
sections. The follow was stopped for about ten years with no new
rubblization of any variety.

In 2009
the WVDOH created a activity drive to enhance pavement life all through the state.
One merchandise born out of the duty pressure was a nine-year guarantee program that
allowed contractors to decide on the rehabilitation technique and the pavement sort.
All eight of the warranty tasks constructed so far have utilized
rubblization with seven to 9 inches of latest HMA, relying on the visitors.
The freeway division discovered from what the contractors trusted to ensure
superior efficiency via the life of the guarantee – rubblization. In 2015,
a new WV specification was written and accepted for using rubblization
around the state.

Rubblization gear and operation

There are
two primary forms of rubblization gear and know-how obtainable within the
United States: the resonant breaker manufactured by RMI and the multi-head
breaker (MHB) manufactured by Antigo. Each rubblization technologies have been
used efficiently on many tasks throughout the world.

On the
WVDOH warranty tasks, the contractors might select from each rubblization
applied sciences and selected to use MHB gear. With a purpose to optimize the
rubblization process, contractors labored intently with Antigo personnel to
customize the gear setup and operation for every specific undertaking.

The MHB
Badger Breaker® has sixteen drop hammers mounted laterally in pairs
with half of the hammers in a forward row and the remainder diagonally offset
in a rear row providing continuous breaking of up to thirteen ft vast. The
hammers differ in weight from 1,200 to 2,000 kilos with the choice of hammers
utilized based mostly on the power required to adequately fracture the particular
concrete pavement. The drop peak of every pair of hammers is independently
adjustable to make sure the right amount of breaking throughout the width of the
machine. The journey velocity of the MHB is adjusted to differ the spacing between
hammer hits.

Matt Shinners
of Antigo talked about elements that must be thought-about when establishing the
MHB for a selected challenge: “The help offered by the subgrade and base
considerably affects the particle sizing that’s achievable. Usually, the
higher the help the smaller and extra consistent the particles may be
produced. The mixture of hammer weights, drop heights and machine velocity
permit the MHB to carry out the optimum rubblizing pattern for each specific
mixture of concrete pavement and subgrade/base help to satisfy the
specification requirement for particle measurement.”

Drainage

The
local weather of West Virginia is assessed as moist and chilly. Draining stormwater
away from the pavements is among the keys to long run efficiency. Poor
drainage typically causes weak subgrade and help circumstances that may inhibit the
rubblization course of. The installation of longitudinal edge drains previous to
rubblization is really helpful for all rubblization tasks, until a
well-functioning drain system exists, or the subgrade consists of self-draining
materials similar to sand. If trapped water beneath the slabs is just not drained, it
will intrude with the rubblization process.

Based mostly on
their previous expertise, WVDOH knew that installing edge drains as part of the
rubblization course of won’t only take away water in the pavement and underlying
supplies initially which make it easier to rubblize however will continue to
provide long-term drainage – enhancing performance. Ideally, the drainage
system must be installed and functioning at the least two weeks previous to the
precise rubblization course of so the subgrade can dry out. On the WVDOH tasks,
edge drains have been installed nicely before the start of the rubblization
course of.

Development

WVDOH
Specifications for “Rubblization of Portland Cement Concrete Pavement” have the
following necessities for either the resonant breaker or multi-head breaker
rubblization applied sciences.


Specification requirements for Resonant Breaker embrace: “The gear will
include a self-contained, self-propelled resonant frequency pavement
breaking unit able to producing low amplitude, 2,000 lbs. blows, at a price
of not lower than 44 per second.”


Specification necessities for Multi- Head Breaker have been that the gear must
again be, “self-contained, self-propelled” and have the “functionality of
rubblizing pavement as much as 13 ft in width, in a single move.”

All the
pavements scheduled for rubblization have been “composite” pavements which means that
they are present concrete pavement with an asphalt overlay. The underlying
concrete had varying thicknesses of asphalt overlays and even patches in some
areas. Before rubblization might take place, the asphalt overlay had to be
eliminated. As well as, WVDOH specifications said that any patches larger than
three sq. ft have been to be removed from the PCC pavement.

The
specifications state that the rubblization course of shall include:

• On the
floor, the gear shall break the pavement such that 75 % of the
particles (by weight) are a most of two inches.

• Under
the reinforcing steel or in the lower a part of the concrete depth, 75 % of
the particles (by weight) are a most of nine inches.

• Concrete
to steel bond can be damaged. Remove reinforcing steel uncovered at the floor
however depart unexposed metal in place.

• Particle
measurement ought to be verified with check pits firstly and at the very least one every
mile throughout the venture.

• Previous to
putting the asphalt overlay, the entire width of the damaged pavement shall be
compacted by vibratory steel wheel and pneumatic tire rollers within the following
sequence:

1.) After
breaking, a minimum of four passes with a z-pattern metal grid curler, four
further passes with a regular vibratory curler and two passes with a
pneumatic tire curler have been required

2.) Just
previous to the overlay, a minimal of two passes of the vibratory curler was
required.

After
rubblization and surface prep, Superpave asphalt overlays have been positioned in
multiple lifts to a depth of sometimes nine inches.

2017 change order

During
2017, 20 lane miles of composite pavement on U.S. 119 have been programmed to have
the previous HMA overlay removed and concrete pavement repaired and diamond floor.
Once the concrete was uncovered, it was straightforward to see that it couldn’t stand up to
visitors, even after repairs. The contractor proposed utilizing rubblization and a
new HMA overlay to place the roadway again into service. This proposal was
accepted and the DOH is proud of the efficiency and prolonged service life.

2018 and 2019 WVDOH tasks

In an
effort to use elevated funding correctly, the WVDOH management tasked pavement
employees with recommending tasks that might last more than the bonds however
could possibly be constructed shortly to point out the general public that their help was
warranted. An inventory of tasks around the state was developed utilizing the state’s
present Pavement Management System. Subsequently, within the fall of 2017 the
WVDOH awarded 12 reconstruction tasks for composite pavements on the
interstate system. These tasks have been meant to be constructed in 2018 and
2019 and totaled 60 centerline miles of roadway.

The 12
tasks that have been awarded in the fall of 2017 confirmed the residents of West
Virginia that their tax dollars have been being spent on the street community that was
in want of rehabilitation. Six of the tasks required the contractor to use
rubblization on the PCC pavement, the opposite six used the nine-year warranty specification.
Contractors might choose any rehabilitation technique that they needed to and all
of them ended up deciding on the rubblization choice.

Matt
Shinner, vice chairman of Antigo Development said “Rubblization exercise
ticked up nicely in 2018 all due to one state’s program. The West Virginia
DOT let twelve tasks that may embrace 1.eight million sq. yards of
rubblization to be carried out in 2018 and 2019.”

For the
2019 development season there are two extra main rehabilitation tasks
deliberate for West Virginia, traditionally these tasks have gone to contractors
who choose to rubblize to realize long term efficiency. Walbeck says, “I’m a
proponent of balancing our program. We’d like rubblization fashion tasks to
handle composite pavement which are a maintenance burden on our individuals. These
reconstruction tasks coupled with preservation of excellent pavements give us the
stability to realize floor in our pavement condition statewide.”

Way forward for rubblization in WV

Via
the monitoring of pavement circumstances in West Virginia, the DOH has documented
that the warranty pavements, utilizing rubblization, are out-performing traditional
full depth new development pavements. The prevailing subgrade and the agency
foundation that rubblized PCC supplies is an enormous a part of this improve in
performance. This has given employees like Walbeck the info to point out determination makers
the good thing about absolutely rubblizing PCC.

The
contractors in West Virginia have welcomed this course of as properly. When asked
about this new wave of work in West Virginia, Chad Miller, the Quality Supervisor
of JF Allen Development stated, “I’d wish to see us rubblize the remainder of the
composite pavement across the state. This process is going to make our asphalt
pavements final lots longer.” The condition of the earlier rubblization
tasks exhibits this.

With
asphalt overlays on the standard West Virginia composite pavement solely lasting
approximately ten years, this variation in philosophy has been needed. Continuing
to only tackle the system with 1.5 to 2-inch mill and fill tasks shouldn’t be
extending the life of the system. The info from the initial rubblization
tasks show that the prolonged performance can be well worth the further
up-front value. That is true not only for the subsequent resurfacing cycle, but the
maintenance crews who’ve been charged with preventing the reflective cracking
and holding the street acceptable between overlays.

Walbeck is a former State Pavement Engineer for WVDOH and is now Training Manager for the National Middle for Asphalt Know-how. Horan is an Asphalt Institute Senior Regional Engineer based mostly in Virginia.