SS309-002020-01 .docx
DOCX document 31 KB Posted
- Attached to
- Construction, University Drive Bike Lanes
- Solicitation number
- IFB-114424
- Issued by
- Fairfax County, Virginia
About this file
This is a supplemental specification document issued by the Virginia Department of Transportation establishing amended guidelines for aggregate base course construction on road and bridge projects, effective July 13, 2021. The specification addresses material density requirements, compaction procedures, and quality control standards for base course aggregate materials used in transportation infrastructure projects. The document modifies Section 309.05 of the Virginia Department of Transportation's 2020 Road and Bridge Specifications to establish revised density requirements based on the percentage of material retained on a No. 4 sieve, with minimum density percentages ranging from 90 percent to 100 percent depending on material composition. Contractors must spread and compact materials in layers of approximately equal thickness, not exceeding 6 inches per layer when compacted, though the Engineer may approve depths up to 10 inches when special compacting equipment is used.
The specification requires contractors to maintain compaction at optimum moisture within 2 percentage points of optimum after mixing and shaping, with density verification performed through portable nuclear density gauge testing using the density control strip method specified in Section 304 and VTM-10, or through other Engineer-approved methods. Density requirements may be reduced by 5 percent when using a portable nuclear density gauge in direct transmission mode. Contractors must maintain uniform surface texture during compaction operations, apply water uniformly as necessary to achieve proper density, and correct surface irregularities through scarifying, remixing, reshaping, and recompacting until Engineer acceptance is secured. The specification emphasizes ongoing surface protection and maintenance of smooth conditions until final acceptance by the Engineer, with depth acceptance criteria referenced in Section 308.
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Guidelines: Use on all projects.
SS309-002020-01 July 13, 2021
VIRGINIA DEPARTMENT OF TRANSPORTATION
2020 ROAD AND BRIDGE SUPPLEMENTAL SPECIFICATIONS
SECTION 309 – AGGREGATE BASE COURSE
SECTION 309 – AGGREGATE BASE COURSE of the Specifications is amended as follows:
Section 309.05 – Density Requirements is replaced by the following:
The Contractor shall spread and compact the material in two or more layers of approximately equal thickness where the required thickness is more than 6 inches. The compacted thickness of any one layer shall be not more than 6 inches, however the Engineer may approve increasing the compacted depth of a single layer of the base course to 10 inches when vibrating or other approved types of special compacting equipment are used.
The Contractor shall compact each layer at optimum moisture within ±2 percentage points of optimum after mixing and shaping. The density of each layer of base aggregate material, when compared to the theoretical maximum density as determined in accordance with VTM-1, shall conform to the following:
| % Material Retained on No. 4 Sieve |
| Min. % Density |
| 0-50 |
| 100 |
| 51-60 |
| 95 |
| 61-70 |
| 90 |
Percentages shall be reported to the nearest whole number. The above density requirements may be reduced by 5% per VTM-10 when using the portable nuclear density gauge in direct transmission mode.
The base course will be tested in place for depth and density. The Department will perform field density determinations with a portable nuclear density gauge using the density control strip as specified in Section 304 and VTM-10, or by other approved methods as directed by the Engineer.
The Contractor shall maintain the surface of each layer during the compaction operations in a manner such that a uniform texture is produced and the aggregates are firmly keyed. The Contractor shall uniformly apply water over the base materials during compaction in the amount necessary to obtain proper density.
Irregularities in the surface shall be corrected by scarifying, remixing, reshaping, and recompacting until a smooth surface is secured. The surface shall thereafter be protected against the loss of fine materials by the addition of moisture, when necessary, and shall be maintained in a satisfactory and smooth condition until accepted by the Engineer.
The Engineer will base acceptance of the aggregate base course for depth on the requirements of Section 308.
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