Section 2115.  Modified Subbase


2115.01     Description.

Construct a subbase consisting of a uniform mixture of uniformly moistened granular materials.


2115.02     Materials.

Apply Section 4123.


2115.03     construction.

Place, shape and compact materials according to the contract documents.


A.    Equipment.


1.     Apply Article 2001.05, Paragraphs B, C, D, and F, except use rollers having a minimum compactive effort of 300 pounds per inch (5.25 kg/mm) width.


2.     Other types of equipment may be used provided it is demonstrated they will consistently produce the required compaction without excessive aggregate breakdown. For all other equipment used, meet the other requirements of Section 2001.


B.    Modified Subbase Construction.


1.     Preparation of Subgrade.

Apply the requirements of Section 2109. In addition, disk the subgrade to a depth of 6 inches (150 mm), aerate, and recompact. Recompact to the requirements of Article 2107.03, E, on Primary projects and Article 2107.03, F, on Secondary projects. Proof roll after preparing subgrade.


2.     Proof Rolling of Subgrade.

Proof roll with a truck loaded to the maximum single legal axle gross weight (mass) of 20,000 pounds (9.1 Mg) or the maximum tandem axle gross weight (mass) of 34,000 pounds (15.4 Mg). Operate the truck at a speed less than 10 mph (16 km/h). Make one pass on every lane. The subgrade will be considered unstable if, under the operation of the loaded truck, the surface shows yielding or rutting of more than 2.0 inches (50 mm) measured from the top to the bottom of the rut at the outside edges. Correct unstable subgrade according to Section 2109.


3.     Delivery of Materials.

Maintain a clean aggregate interface between the granular subbase material and the porous backfill material of longitudinal subdrains.


4.     Placing and Compacting Modified Subbase.

a.     Ensure modified subbase material is uniformly moist prior to and during compaction.

b.     Place modified subbase in uniform lifts no more than 6 inches (150 mm) thick.

c.     Compact modified subbase with a minimum of six roller passes.

d.     Profile and cross section tolerances for modified subbase are +0 feet to -0.05 feet (+0 mm to -15 mm).


2115.04     Method of Measurement.

Modified Subbase will be the quantity shown in the contract documents.


2115.05     Basis of Payment.


A.    Payment for Modified Subbase will be the contract price per cubic yard (cubic meter).


B.    Payment is full compensation for furnishing all materials, water, preparation of subgrade, and for all work necessary to complete the modified subbase in compliance with contract documents.


C.    The contract will have a separate item for Modified Subbase, Place Only, in cubic yards (cubic meters), when the Contracting Authority is providing the material or if the material is available from mandatory crushing on the contract. The cost of crushing shall be included in the Contractor's price bid for modified subbase if recycling is not required, but the Contractor chooses to crush the pavement removed for modified subbase.


D.    Excavation or filling in excess of 3 inches (75 mm) for preparation of subgrade at locations other than structures or existing pavements will be paid for according to Article 2102.05, or if no contract unit price is provided, it will be paid as extra work according to Article 1109.03, B, except where grading is a part of the contract.


E.    Correction of subgrade after proof rolling will be paid as extra work according to Article 1109.03, B, except where grading is a part of the contract.