SECTION 309—AGGREGATE BASE COURSE
309.01 Description
This work shall consist of furnishing and placing one or more courses of aggregates and additives, if required, on a prepared surface in accordance with these specifications and in conformity with the lines, grades, and typical sections and cross sections shown on the plans or as established by the Engineer.
309.02 Materials
a.Aggregate material shall conform to Section 208.02(b) except where other types of aggregate material are specified in the contract, in which case the applicable specifications governing the specified material shall apply.
b.Calcium chloride and sodium chloride shall conform to Section 239.
309.03 Equipment
The Engineer will approve the equipment used for the construction of aggregate base course prior to performance of such work. Any machine, combination of machines, or equipment that handles the material without undue segregation and produce the completed base in accordance with these specifications for spreading, moistening, mixing, and compacting will be acceptable to the Engineer.
309.04 Procedures
The Contractor shall prepare the surface or course upon which the base course is to be placed in accor - dance with the applicable provisions of Section 304 and Section 305. 308.05 Base course material shall be mixed in an approved central mixing plant of the pugmill type. The Contractor shall place the mixed material by means of an approved aggregate spreader.
309.05 Density Requirements
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. Not more than one sample in every five shall have a density less than that specified, and the density of such sample shall be not more than 2 percent below that specified. 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 base course will be tested in place for depth and density. The Department will perform field density determinations with a portable nuclear field density testing device using a density control strip as specified in Section 304 and VTM-10 or by other approved methods as directed by the Engineer. The Engineer will base acceptance of the aggregate base course for depth on the requirements of Section 308.
309.06 Measurement and Payment
Aggregate base course will be measured in cubic yards or tons, as specified, and will be paid for at the contract unit price per cubic yard or ton for the aggregate type and number specified. When the cubic yard unit is specified in the contract, the quantity will be determined by compacted measurements on the road unless otherwise specified. When the ton unit is specified, the quantity shall be determined in accordance with Section 109.01. The Engineer will make a deduction from the net weight of both truck and rail shipments for moisture in excess of optimum + 2 percentage points. 309.06
Referenced in this section
Sections that cite this one
Aggregate Base Course in other states
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Source: Road and Bridge Specifications, 2020 Edition. Pages 406–407 of 1,065. View official source ↗