3-4 Section 302. Aggregate Base Course
302.01 Description
This work consists of constructing an aggregate base course on a surface approved by the Engineer.
302.02 Materials
Provide materials in accordance with the following section : Dense-Graded Aggregate 21AA, 21A, 22A ........................................... 902 Provide aggregate meeting the aggregate series shown on the plans.
302.03 Construction
A.Placing and Compacting . Provide a ticket with each load stating the following information:
1.Project number ;
2.Aggregate source;
3.Aggregate series ;
4.Date;
5.Time ;
6.Truck identifier number ;
7.Supplier name; and
8.Type of aggregate approval. If the contract requires payment by weight, ensure the ticket includes the gross weight, tare weight, and net weight to the nearest 100 pounds. Determine the truck tare weight at least once daily. If the contract does not require payment by weight, the Engineer may accept written documentation instead of tickets. Written documentation must identify the pay item of the material and include all of the information listed above except time and truck identifier number. Provide and place aggregate with a uniform gradation, free of contamination and segregation. Do not place aggregate base on frozen, soft, unstable or rutted subgrade, subbase, or aggregate base. Do not rut or distort the s ubbase material or aggregate base during spreading. The Contractor may use additives to facilitate compaction, shaping, and maintenance of the aggregate surface. MDOT Standard Specifications for Construction Section 302 3-5 Compact the aggregate layers to a uniform thickness, no less than 3 inches and no greater than 8 inches. If placing aggregate base in a layer less than 3 inches, blend the new aggregate base material with the layer below to ensure a total of 6 inches. Blending must be performed to ensure that the new aggregate base material is uniformly mixed with the layer below. Compact each layer of aggregate base to at least 98% of the maximum unit weight at a moisture content no greater than optimum for aggregate base under hot mix asphalt (HMA) pavement. Compact each layer of aggregate base to at least 95 % of the maximum unit weight at a moisture content no greater than optimum for aggregate base under concrete pavement. Within the limits of bridge approaches, from the abutment wall to the typical roadway cross section, compact each layer of the aggregate base to at least 98% of the maximum unit weight. Shape the finished surfac e and the layer thickness to within ±½ inch of the crown and grade shown on the plans. Remove, dispose of, and replace aggregate base material that mixes with subbase or subgrade material at no additional cost to the Department.
B.Conditioning Aggregate Base . Shape the finished surface of the existing aggregate base course to within ±½ inch of the grade and cross section shown on the plans. Provide additional aggregate to address irregularities and obtain the required grade or cross section. If placing aggregate base in a layer less than 3 inches, blend the new material with the layer below to ensure a total of 6 inches. Blending must be performed to ensure that the new material is uniformly mixed with the layer below and compact ed as specified in subsection 3 02.03.A.
C.Maintenance During Construction . Maintain the aggregate base course layer at the required line, grade, and cross section until placement of the next layer. Ensure the exposed aggregate base course layer remains smooth, compacted, and uncontaminate d. If the subgrade, subbase, or aggregate base is damaged due to the Contractor’s operations or construction traffic, restore to the required condition at no additional cost to the Department.
D.Surplus Existing Aggregate Base Material. Surplus existing aggr egate base material meeting the material requirements described in this section may be used instead of providing new aggregate base material. Remove and dispose of surplus aggregate base material not being used elsewhere on the project and any unsuitable material in accordance with subsection
205.03 P.
MDOT Standard Specifications for Construction Section 302 3-6 302.04. Measurement and Payment Pay Item Pay Unit Aggregate Base ........................................................................................... Ton Aggregate Base, LM ........................................................................ Cubic Yard Aggregate Base, __ inch ............................................................... Square Yard Aggregate Base, Conditioning .......................................... Station, Square Yard Aggregate Base, Conditioning, Surplus and Unsuitable, Rem, LM ............................................................ Cubic Yard Salv Aggregate Base, Conditioning, LM .......................................... Cubic Yard
A.Aggregate Base. The Engineer will determine the moisture content and pay weights in accordance with section 109. The Engineer will measure Aggregate Base by the scale weight of the material, including admixtures, and moisture content no greater than 8 %. The Engineer will perform moisture tests at the start of weighing operations and if construction operations, weather conditions, or other causes may change the moisture content of the material. If tests indicate a moisture content greater than 8% , the Engineer will deduct the weight of the excess moisture from the scale weight of the aggregate until moisture tests indicate the moisture content is no greater than 8 %.
B.Aggregate Base, LM. The Engineer will measure Aggregate Base, LM based on hauling unit dimensions and load count before placement and compaction. The unit price for Aggregate Base, LM includes the cost of providing, hauling, placing, compacting, and grading the material and providing water for compaction.
C.Aggregate Base, __ inch. The Engineer will measure Aggregate Base, __ inch by width and length for the specified depth as shown on the plans.
D.Aggregate Base, Conditioning . If the contract requires payment for Aggregate Base, Conditioning in station pay units, the Engineer will measure along the alignment of the roadway. If the contract requires payment for Aggregate Base, Conditioning in area pay units, the Engineer will measure by the width and length shown on the plans. If the contract does not include the pay item Aggregate Base, Conditioning , the Department will consider the cost of conditioning aggregate base and of providing additives and water for compaction and maintenance to be included in other aggregate base pay items.
E.Aggregate Base, Conditioning, Surplus and Unsuitable, Rem, LM. The Department will pay for Aggregate Base, Conditioning, Surplus MDOT Standard Specifications for Construction Section 302 3-7 and Unsuitable, Rem, LM only if the Contractor removes material from the project si te and disposes of it in accordance with subsection 205.03.P.
F.Salv Aggregate Base, Conditioning, LM . The Department will pay for Salv Aggregate Base, Conditioning, LM for use in other areas of the project only if existing aggregate base material requires loading and hauling. The Engineer will measure and the Department will pay for as Salv Aggregate Base, Conditioning, LM surplus material that is loaded and hauled from locations on the project to other locations in order to attain the plan grade or cross section. The Engineer will measure the material in its final location.
Source: Michigan Standard Specifications for Construction, 2020 Edition. Pages 179–182 of 1,146.