SECTION 02726
SUB-BALLAST
PART 1 – GENERAL
1.01
DESCRIPTION:
A.
1.02
QUALITY ASSURANCE:
A.
B.
C.
1.03
This section specifies furnishing, placing and compacting sub-ballast on previously
constructed subgrade.
Codes, Regulations, Reference Standards and Specifications:
1.
Comply with codes and regulations of the jurisdictional authorities.
2.
ASTM: C88, C117, C127, C131, C136, C142, D698, D6938.
Source of Materials:
1.
Obtain approval of sub-ballast prior to commencing installation.
2.
Do not change material or source of supply without approval.
Inspection:
1.
The Engineer has the right to stop delivery of material to the job site based on visual
inspection pending sampling and testing.
2.
If material loaded, being loaded or installed does not conform to specified
requirements, the Engineer will reject the material and no further delivery will be
accepted until the deficiency is corrected.
3.
Replace defective material.
SUBMITTALS:
A.
Submit the following for approval in accordance with the General Requirements and with the
additional requirements as specified for each:
1.
Certification.
2.
Samples and Documentation:
a.
Qualification: Submit samples and source of supply sufficiently in advance
to obtain approval not less than 30 days prior to anticipated date of
commencing installation.
PART 2 – PRODUCTS
2.01
MATERIALS:
A.
Sub-Ballast: Crushed stone, with the following additional requirements:
1.
Gradation: ASTM C136 and ASTM C117 with the following additional
requirements:
Sieve Size
1 inch
3/8 inch
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Percent Passing By
Weight
100
50 to 85
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4
10
40
200
a.
35 to 65
25 to 50
15 to 25
5 to 15
Fraction passing the Size 200 sieve less than two thirds of fraction passing
Size 40 sieve.
2.
Clay lumps and friable particles: ASTM C142, 0.5 percent maximum.
3.
Wear: ASTM C131, 40 percent maximum.
4.
Absorption: ASTM C127, 0.5 percent maximum.
5.
Soundness: ASTM C88, weighted average loss 15 percent maximum after five cycles
of magnesium sulfate tests.
PART 3 – EXECUTION
3.01
PLACING MATERIAL:
A.
The subgrade shall have been graded, shaped and compacted as required by the plans and
specifications. A uniformly smooth surface compacted to specifications is required,
containing no ruts, pot holes, loose soil or any imperfection retaining water on the surface.
The surface shall be inspected by the engineer and if surface fails to conform to specifications
the engineer may require blading, rolling and compacting to provide a satisfactory surface.
B.
Do not place material on subgrade that is muddy, rutted or frozen or has standing water.
C.
The sub-ballast material shall be transported and delivered to the site in a manner that will
prevent separation or loss of material.
D.
Prior to placing materials, repair subgrade using sub-ballast.
E.
Place material to provide uniformity of grading throughout work.
F.
If subgrade is dusty, sprinkle it prior to placing sub-ballast.
G.
Install sub-ballast to shape and compacted thickness shown.
H.
3.02
3.03
1.
Where compacted thickness is six inches or less, place sub-ballast in one layer.
2.
Where compacted thickness is more than six inches, place material in two or more
layers of equal thickness of not more than six inches each.
Vehicular traffic is to be kept to a minimum across the newly prepared sub-ballast surface.
The contractor shall be responsible for maintaining a firm, true and smooth surface
compacted to the required density until track ballast is placed on the sub-ballast.
COMPACTION:
A.
During placing and compacting, maintain moisture content within specified tolerance.
B.
Compact material for its full depth to 100 percent of maximum dry density.
FIELD QUALITY CONTROL:
A.
Allowable Tolerances:
1.
Construct surface of sub-ballast to the following tolerances:
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2.
B.
a.
Within 0.1 foot of elevation shown.
b.
Deviation not more than ½ inch from 10-foot straightedge.
During compaction maintain moisture content within two percent of optimum
moisture content.
Tests:
1.
Determine optimum moisture content and maximum dry density in accordance with
ASTM D698.
2.
Determine in-place density and moisture content in accordance with ASTM D6938.
END OF SECTION
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