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Cement-Treated Base Case
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> Dulles Airport Runway 4
Cement Trifecta at Dulles Airport
Three different cement products are being used in the construction
of new Runway 4 at Dulles International Airport in Washington, DC:
- Soil-cement is being used to stabilize the subgrade
- A cement-treated base (CTB) is being constructed on top of the
stabilized subgrade
- The runway surface is jointed concrete pavement
The new runway will be approximately 9,400 ft. long and 150 ft.
wide, in addition to the accompanying taxiways. The project started
in 2006 and will be completed in 2008.
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| Layout of Dulles International Airport, Washington,
D.C. |
The cement stabilization of the subgrade will provide an excellent
working platform for the entire project. The existing subgrade soils
are very moisture sensitive, and when disturbed after a rain will
turn to mud, causing extensive and very costly construction delays.
The entire project area will be treated with soil-cement, which
is not moisture sensitive, thereby eliminating this type of construction
delay and providing a stable platform for the pavement structure.
The CTB will provide a gradual increase in stiffness for the pavement
structure, bridging between the subgrade soils to the rigid concrete
slab. In addition, the CTB is placed to very precise elevation using
laser grade control, which provides an excellent construction platform
for paving the concrete runway.
Slurry Pavers, Inc., a Virginia based contractor, is doing the
subgrade stabilization by pulverizing and mixing 5% cement (45 lbs/sy)
to a depth of 12 inches using a Wirtgen WR2500 pulverizer/mixer.
The subgrade in this area of the airport property is a weathered
sandstone, and in some locations it required three passes of pulverization
to reduce the material to the required 80% passing the # 4 sieve.
The current project is 600,000 square yards of subgrade stabilization,
with typically 6,000 – 8,000 square yards a day production.
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| Mixing soil-cement for subgrade stabilization |
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| Compaction of soil-cement. |
The cement-treated base (CTB) is being constructed by Lane Construction,
Inc.. The CTB is 6 inches thick, and is being placed with high-density
ABG and Vogele pavers. The aggregate for the CTB is being plant-mixed
on site using 6% cement.
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| Placing CTB with high-density paver |
The concrete runway is typically 18 inches thick, with doweled
transverse joints on a 20 ft. spacing. The use of the cement-stabilized
subgrade follows a similar project constructed in 2004, when soil-cement
was used on the construction of Runway 12.
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| New concrete pavement on CTB. |
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