SECTION 301 – SUBBASE
301.01 Description
This Section describes the requirements for constructing one or more courses of subbase.
301.02 Materials
301.02.01 Materials
Provide materials as specified: Soil Aggregate (I-3) ................................ ................................ ................................ ................................ ...... 901.11
301.02.02 Equipment
Provide equipment as specified: Pneumatic-Tired Compactor ................................ ................................ ................................ ........................ 1002.01 Dynamic Compactor ................................ ................................ ................................ ................................ ... 1002.02 Steel-Wheel Roller ................................ ................................ ................................ ................................ ...... 1002.03 Padfoot Roller ................................ ................................ ................................ ................................ ............. 1002.04
301.03 Construction
301.03.01 Subbase
A.Preparing Subgrade. Before placing subbase, ensure that the subgrade has been graded and compacted, as specified in 203.03.02.B.3, to within a tolerance of 1/2 inch of the required elevation. The RE will check elevations of the roadbed subgrade as specified in 202.03.03.D. Do not prepare the subgrade during freezing weather, when frozen, or when it is unstable. Correct damage to the subgrade caused by construction activities and maintain the corrected subgrade until the subsequent course is placed.
B.Spreading and Grading. Do not place subbase material when the subgrade is frozen or unstable. Notify the RE if the finished subgrade is unstable and obtain RE approval before removing unstable material. Backfill the area with suitable material and compact using the directed method as specified in 203.03.02.B.3. Spread the subbase material with equipment except in limited or restricted areas where the use of hand spreading is allowed. If approved by the RE, end-dump the subbase material. Spread the subbase material in a manner that does not break down material and eliminates segregation, ruts, and ridges.
C.Compacting. Place the subbase in 8 inch maximum lifts and compact within a tolerance of 1/2 inch of the required elevation. For subbase courses greater than 8 inches thick, construct the subbase course in 2 or more lifts of approximately equal thickness. Begin compacting at the sides and gradually progress to the center. On superelevated curves, compact from the lower to the upper edge, parallel to the centerline, and uniformly overlap each preceding track until the entire surface has been compacted. If constructing concrete base or surface courses directly on subbase, the ME will measure the compaction using the density control method as specified in 203.03.02.B.4. If constructing aggregate base course or HMA on the subbase, the ME will measure compaction using the control fill method as specified in 203.03.02.B.2. Correct damage to the subbase caused by construction activities , and maintain the corrected subbase until the subsequent course is placed. Do not allow traffic on the subbase. Remove all standing storm water and obtain the RE’s approval before constructing subsequent courses.
Referenced in this section
Sections that cite this one
Subbase in other states
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Source: Standard Specifications for Road and Bridge Construction, 2019 (rev. 2022-12-21) Edition. Pages 176–176 of 651. View official source ↗