Diamond grinding of pavement
From Wikipedia, the free encyclopedia
Diamond grinding is a pavement preservation technique that corrects a variety of surface imperfections on
both concrete and asphaltpavements. Most often utilized on concrete pavement, diamond grinding is typically
performed in conjunction with other concrete pavement preservation (CPP) techniques such as road slab
stabilization, full- and partial-depth repair, dowel bar retrofit, cross stitching longitudinal cracks or joints and joint
and crack resealing.[1] Diamond grinding restores rideability by removing surface irregularities caused during
construction or through repeated traffic loading over time. The immediate effect of diamond grinding is a
significant improvement in the smoothness of a pavement. Another important effect of diamond grinding is the
considerable increase in surfacemacrotexture and consequent improvement in skid resistance, noise reduction
and safety.
Contents
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1 History
2 Process
3 Applications
4 Cost-effectiveness
5 Advantages
6 References
7 External links
8 See also
[edit]History
The industry can be traced back to an event where a single diamond blade mounted on a concrete saw was
used to groove concrete pavement in the late 1940s. Since that early tentative step, concrete grinding,
grooving and texturing with diamond blades has developed into what is today a multimillion dollar industry that
is practiced worldwide.[2]
One of the first uses of diamond grinding of highway pavement was in 1965 on a 19-year-old section
of Interstate 10 in California to eliminate excessive faulting. The pavement was ground again in 1984 and in
1997, and it is still carrying heavy traffic today, more than 60 years after it was first constructed. [3]
[edit]Process
Results of diamond grinding of pavement
Diamond grinding involves removing a thin layer at the surface of hardened PCC using closely spaced diamond
saw blades. The level surface is achieved by running the blade assembly at a predetermined level across the
pavement surface, which produces saw cut grooves. The uncut concrete between each saw cut breaks off
more or less at a constant level above the saw cut grooves, leaving a level surface (at a macroscopic level)
with longitudinal texture. The result is a pavement that is smooth, safe, quiet and pleasing to travel. [1]
The diamond blades are composed of industrial diamonds and metallurgical powder. When grinding materials
contain hard aggregate materials, a diamond blade with a soft bond is needed, which means that the
metallurgical powders in the cutting segments of the blade wear fast enough to expose the diamond cutting
media at the proper rate for efficient cutting. Conversely, to cut soft aggregates, a diamond blade with a hard
bond is recommended.
Diamond grinding should not be confused with milling or scarifying. Milling is an impact process that chips small
pieces of concrete from the pavement surface. Diamond grinding is a cutting process.
For grinding asphalt to remove old pavement, see asphalt milling machine.
[edit]Applications
There are many surface issues that diamond grinding can improve or correct. Some of the surface
imperfections that can be addressed by diamond grinding include: faulting at joints and cracks, built-in or
construction roughness, polished concrete surfaces exhibiting inadequate macrotexture, wheel path rutting
caused by studded tires, unacceptable noise level, slab warping caused by moisture gradient and construction
curling, inadequate transverse slope and splash and spray reduction. [1]
[edit]Cost-effectiveness
Diamond grinding is a cost-effective treatment, whether used alone or as part of an overall concrete pavement
restoration (CPR) program. In most cases, the cost of diamond grinding is only about half the cost
of bituminous overlays.[4] This cost competitiveness, in conjunction with eliminating bituminous overlay
problems (rutting, corrugation, poor skid resistance, drainage reduction, vertical clearance reduction) makes
diamond grinding an alternative for many rehabilitation projects. Diamond grinding can be used as part of any
preventive maintenance program for concrete pavements.
The California Department of Transportation (CALTRANS) reports that the average life of a diamond-ground
surface is between 16 to 17 years. On average, more than 2,000 lane-miles of concrete pavement are diamond
ground every year.[3][5][6][7][8][9][10]
[edit]Advantages
Diamond grinding is used to restore or improve pavement ride quality. Restoring ride through grinding improves
traffic carrying capacity and adds value to an in-place pavement. Diamond grinding provides numerous benefits
over other rehabilitation alternatives.
This repair technique also provides a smooth surface which is often as good as new pavement. [1] As trucks
travel across bumps and dips, they bounce vertically on their suspension resulting in dynamic loading. The
increased load due to dynamic impact results in higher stresses in the pavement materials and consequently
lower road life by providing an extremely smooth surface. Diamond grinding limits dynamic loading. [4]
Another advantage is reduced road noise. Diamond grinding's longitudinal texture provides a quieter surface
than most transverse textures. A multi-state study on noise and texture on PCC pavements concluded that
longitudinal texture concrete pavements are among the quietest pavements for interior and exterior noise.
[11]
Diamond grinding also removes faults by leveling the pavement surface, thus eliminating the thumping and
slapping sound created by faulted joints.
Enhanced surface texture and skid resistance is another advantage of diamond grinding. The corrugated
surface increases surface macrotexture and provides ample channels for water to displace beneath vehicle
tires, reducing hydroplaning potential.[4][12][13] Diamond grinding also improves cornering friction, providing
directional stability by tire tread-pavement groove interlock.
Diamond grinding has been found to reduce accident rates. The increased macrotexture provides for improved
drainage of water at the tire-pavement interface, thus improving wet-weather friction, particularly for vehicles
with balding tires. The longitudinal nature of a diamond-ground texture also provides directional stability and
reduces hydroplaning, thus contributing to the safety of diamond ground surfaces. [1][14][15]
This technique does not significantly affect fatigue life. The reduction in thickness due to diamond grinding is
highest at the faulted joint and lower at the interior. The small reduction in slab thickness caused by diamond
grinding has negligible effect on service life. A typical concrete pavement may be ground up to three times and
still add traffic carrying capacity. Diamond grinding does not affect material durability. The fact that the
diamond-ground surface is nearly always dry (except during storms) reduces any freeze-thaw problems.
Diamond grinding does not introduce any unusual condition that would lead to poor surface durability. [1]
This preservation method does not raise the pavement surface elevation. Grinding does not affect overhead
clearances underneath bridges and eliminates the need for tapers at highway entrances, exits and at side
streets. Grinding does not affect the hydrauliccapacities of curbs and gutters on municipal streets. On the other
hand, bituminous overlays fill curb and gutter, reducing drainage capabilities.
Diamond grinding should be applied to the portion of the pavement where restoration is needed. [4][12][16] A
highway agency can require grinding only on the truck lanes of a four-lane divided highway, presenting a
significant cost advantage.
Finally, diamond grinding can be accomplished during off-peak hours with short lane closures, without having to
close adjacent lanes. Diamond grinding can also be used on all road classes, from interstates to city streets.
Full-Depth Repair
Full-depth patching entails removing and replacing at least a portion of a slab to the bottom of the concrete,
in order to restore areas of deterioration. Full-depth patches improve pavement rideability and structural
integrity and extend pavement service life.
The most common problem that requires full-depth patching is joint deterioration. This includes any
cracking, breaking, or spalling of slab edges on either side of a transverse or longitudinal joint. Often, this
deterioration takes place on the bottom of the concrete slab and may not be visible from the surface.
Spalls that extend 3–6 inches from the joint are moderately severe and are a sign that more spalling could
exist below. Only below-surface problems require full-depth replacement; for surface spalls partial-depth
repair is usually acceptable.
Full-depth repair also is necessary to repair any corner breaks or any slabs with more than one intersecting
crack. These are both signs of support problems and lack of structural strength.
Punchouts in continuously reinforced concrete pavements require full-depth repair. Punchouts can form after
millions of loads. The longitudinal steel in the slab ruptures along the faces of two closely spaced cracks, and
a small segment of concrete punches into the subbase. Punchouts are usually about 2 ft long. Punchouts can
also occur where transverse cracks split into a Y about 1–3 feet from the edge of a lane.
Most full-depth repairs of joint deterioration or punchouts cover at least 70 square feet. For corner breaks or
slabs with intersecting cracks, their size may correspond to the area of an entire slab (180 square feet for a
15 foot long slab).
Patches are a common method of treating an area of localized distress. Patches can be either fulldepth where they extend from the pavement surface to the subgrade (Figure 1) or partial where they
do not extend through the full depth of existing pavement (Figure 2).
Full-depth patches are necessary where the entire depth of pavement is distressed. Often times, the
underlying base, subbase or subgrade material is the distresses root cause and will also need repair.
Partial depth patches are used for pavement distresses like raveling, rutting, delamination and
cracking where the depth of crack does not extend through the entire pavement depth.
Patching material can be just about any HMA or cold mix asphalt material as well as certain types of
slurries. Typically some form of HMA is used for permanent patches, while cold mix is often used for
temporary emergency repairs.