ITEM 304 AGGREGATE BASE
304.01
Description
304.02
Materials
304.03 Before
Spreading
304.04 Spreading
304.05
Compaction
304.06 Finished
Surface
304.07 Method
of Measurement
304.08 Basis of
Payment
304.01 Description. This work consists of
furnishing, placing, and compacting one or more courses of aggregate on a
prepared surface, including furnishing and incorporating all water required for
compaction.
304.02 Materials. Furnish materials conforming to 703.17.
304.03 Before Spreading. The
Engineer will sample the Contractor’s stockpile to determine the initial
moisture content to be used for compaction. The Engineer will develop a
moisturedensity curve to determine the optimum moisture content.
Use
material that has reasonably uniform moisture content. Ensure the
moisture content is not less than 2 percent below the optimum moisture content
before spreading. Add water to the stockpile if necessary to meet this
moisture requirement.
Handle
the material in a manner to minimize segregation. If segregation occurs,
thoroughly mix or regrade the stockpile.
304.04 Spreading. Spread the material on the
prepared surface. Do not use frozen material and do not spread on frozen
surfaces.
Do
not exceed a compacted lift thickness of 8 inches (200 mm) when using vibratory
rollers with effective weights greater than 12 tons (11 metric tons). Do
not exceed a compacted lift thickness of 6 inches (150 mm) when using vibratory
rollers with effective weights from 10 to 12 tons (9 to 11 metric tons).
Do not exceed a maximum compacted lift thickness of 4 inches (100 mm) when
these vibratory rollers are not used. The effective weight of a vibratory
roller is the weight plus the centrifugal force from vibration. Submit
documentation from the manufacturer that shows the vibratory roller meets the
minimum effective weight requirements.
Place
the material in two or more approximately equal lifts when the specified
compacted thickness exceeds the maximum allowed.
Place
the material with selfpropelled spreading machines capable of placing the
material true to line and grade. Spreading machines such as spreader
boxes or pavers are allowed. Do not use graders or dozers without
spreader boxes to spread the material except for areas described in the next
paragraph. Spread the material such that it minimizes segregation and
requires minimal blading or manipulation. The Department may perform
inplace gradation testing in areas that are visually segregated according to Supplement
1090.
The
Contractor may use handplacing methods, dozers or graders when the total area
of the material is 2000 square yards (1700 m²) or less or in small areas where
selfpropelled spreading machines are impractical. Small areas include
lane widths less than 12 feet (3.7 m) or lengths less than 1000 feet (305
m). The Department will not take inplace gradation tests in these small
areas.
The
Department may test for inplace gradation after spreading but before
compaction testing according to Supplement
1090.
304.05 Compaction. Add water or dry the material to
bring it to within 2 percent of the optimum moisture content before
compacting. Maintain the moisture content within this range during all
compaction operations. The Engineer will determine the percentage of
moisture to apply or to be dried from the material. Uniformly apply the
water or dry the material throughout the lift and in a manner that does not
soften or disturb the lower courses. Reduce the moisture content if the
material becomes unstable during the compaction operation.
Compact
each lift of material immediately after spreading. Use rollers that
correspond with the lift thickness as described in 304.04.
The Contractor may use lighter rollers or vibratory equipment in small areas as
specified in 304.04 or when heavier rollers are
not practical. Approved compaction equipment may consist of vibratory
rollers, static rollers, or vibratory equipment.
At
the beginning of the compaction operation, construct a test section according
to Supplement
1015. Use a minimum compactive effort of eight passes to construct
the test section. Use and adjust the vibration on the vibratory rollers
to maximize the density and stability. Construct a new test section when
the material changes or when the supporting materials change appreciably.
The
Engineer will use 98 percent of the test section maximum dry density for
acceptance of the production material. Use at least the same number of
passes and compactive effort used to obtain the test section maximum dry
density for the production material. At a minimum, use eight passes in
the production area. The Engineer may reduce the minimum passes if the
passes are detrimental to compaction
The
Engineer may check the production material density before or after the
finishing operations.
Maintain
the surface of each lift during the compaction operations in such a manner that
the surface texture is reasonably uniform and the material is firmly keyed.
Cover
the aggregate base with the next layer of pavement before the end of the
construction season. If the aggregate base is not covered up, then assume
all liability for contamination of, damage to and instability of the base,
subgrade and underdrains.
Provide
drainage and maintain the material according to 203.04.A.
304.06 Finished Surface. Ensure
that the finished surface does not vary more than 3/8 inch (10 mm) from a
10foot (3 m) straightedge parallel to the centerline or more than 1/2 inch
(13 mm) from a template conforming to the required crosssection.
Furnish straightedges, templates, or other devices satisfactory to the
Engineer, and check the surface for conformance with these requirements.
Do
not construct the aggregate base at a consistent depth below the required
minimum compacted depth thickness. When the depth is found to be less
than the required depth, provide the Engineer with a written corrective action
plan for approval.
304.07 Method of Measurement. The
Department will measure Aggregate Base by the number of cubic yards (cubic
meters) computed from the profile grade and typical sections, compacted in
place.
Where
variable depth is specified, the Department will measure the number of cubic
yards (cubic meters) of aggregate base by converting from weight using the
following conversion factors:
Material 
Conversion Factor 

Crushed stone 
4000 lb/yd³ 
2375 kg/m³ 
Crushed gravel 
4000 lb/yd³ 
2375 kg/m³ 
Crushed slag ^{[1]} 


less than 90 lb/ft³
(1450 kg/m³) 
3600 lb/yd³ 
2140 kg/m³ 
90 to 100 lb/ft³
(1450 to 1600 kg/m³) 
4000 lb/yd³ 
2375 kg/m³ 
more than 100 lb/ft³
(1600 kg/m³) 
4500 lb/yd³ 
2670 kg/m³ 
Granulated slag 
2800 lb/yd³ 
1660 kg/m³ 
[1] Based on average dry rodded weight of standard size of slag aggregates on
record at the Laboratory. The conversion factors listed are the long
gradation weights. These numbers are based on the dry rodded weights of No. 67, 57, or 8 gradation.
The Department will determine slag weights based on weights obtained from the
original source. 
The
Department will verify that the moisture content of the delivered material is
less than 2 percent above saturated surface dry (SSD).
If the moisture content is greater than 2 percent above SSD,
then the Department will calculate the number of cubic yards (cubic meters)
based on the dry density and dry weight.
The
Department will determine the pounds per cubic yard (kilograms per cubic meter)
for aggregate mixtures by using 100 percent of the test section maximum dry
density obtained in 304.05.
304.08 Basis of Payment. The
Department will pay for accepted quantities at the contract price as follows:
Item
Unit
Description
304
Cubic
Yard
Aggregate Base
(Cubic Meter)