ITEM 307 NON-STABILIZED DRAINAGE BASE

307.01 Description

307.02 Aggregate

307.03 Composition of Mixtures

307.04 Verification of Design

307.05 Equipment

307.06 Mixing and Prewetting

307.07 Transportation of Mixtures

307.08 Preparation ofSubgradeor BaseCourse

307.09 Spreading

307.10 Compaction

307.11 Shaping and Finishing

307.12 Limitations on Placing Operations

307.13 Protection of the Underdrains

307.14 Protection of the Non-Stabilized Drainage Base

307.15 Thickness Tolerances

307.16 Surface Tolerance

307.17 Exposure to the Elements

307.18 Method of Measurement

307.19 Basis of Payment

 

307.01 Description. This work consists of constructing a non-stabilized drainage base (NSDB) on a prepared base course.

307.02 Aggregate. Furnish aggregate conforming to 703.12.

307.03 Composition of Mixtures. A minimum of 30 days before production, submit a computed blend of aggregates for the necessary testing to determine the mix design acceptance.

The mix design will establish the percentage, by dry weight, of aggregate passing each required sieve size. Ensure that the values of percent passing each sieve size are within the master band. Use the submitted gradation until a modification is approved.

307.04 Verification of Design. The Engineerwill verify and approve the mix design.

If required by the Engineer, deliver the necessary component aggregate to the Engineer to verify the design. Notify the Engineer prior to the delivery of the materials.

The Department will take random samples of the material at the discharge from the pugmill mixer, if used, and following the spreading operation to ensure conformance with the mix design.

307.05 Equipment. Ensure that all equipment necessary to mix, transport, place, compact, and finish this layer is approved before beginning work. Such equipment includes:

A. If used, a stationary or portable, continuous or batch type pugmill mixer, equipped with batching or metering devices for proportioning the blend of aggregate and water and capable of producing a blended material consistently meeting the gradation requirements.

B. A traveling plant such as a spreader box or asphalt paver capable of maintaining a uniform rate of travel while spreading or laying a lift of uniform consistency and thickness with proper grade control.

C. Steelwheel static or vibratory rollers. Use 8 to 10 ton (7 to 9 metric tons) steel wheel static roller for Type IA and NJ NSDB. Use a vibratory roller, with a minimum weight or centrifugal force of 10 tons (9 metric tons), to compact the Type CE NSDB.

307.06 Mixing and Prewetting. Prewet and mix the aggregate in the proper proportion as specified in the mix design.

The Contractormay elect to use a pugmill mixer. When elected, use a pugmill mixer that provides an accurate control of the proportions of water and aggregate and retains the material in the mixing chamber for at least 15 seconds of vigorous action. If the mixer is of the continuous-flow type, ensure that it has twin-mixing shafts. Equip the continuous-flow mixer with a hopper or bin at the discharge end of the mixer designed to minimize the segregation of the mixed materials and capable of preventing stoppage of the mixer between successive truckloads under normal operating conditions. If segregated, do not use material at the beginning of the pugmill operation. Operate the pugmill with a smooth and continuous feed to prevent segregation. Furnish materials containing at least 3 percent moisture content above saturated surface dry (SSD) condition before discharging from the mixer. Immediately load the mix into the hauling vehicles. Minimize the drop height to the trucks and minimize the haul distance to prevent segregation.

If electing not to use a pugmill mixer, add water prior to or during the spreading operation to ensure a moisture content of 1.5 percent above SSD after spreading.

Handle the mixture to prevent contamination, degradation, and segregation. Ensure that the final mixture and the in place material conforms to this specification.

307.07 Transportation of Mixtures. Haul the blended material to the site in vehicles that prevent contamination, degradation, and segregation of the mixture.

307.08 Preparation ofSubgradeor BaseCourse. Prepare the subgrade and base course according to the applicable requirements of Item 204 and 304.

307.09 Spreading. Deliver the blended mixture to the prepared subgrade and base course, and spread it uniformly with minimum manipulation to prevent segregation. Place the aggregate in compacted lifts not to exceed 4 inches (100 mm). Use spreader boxes or asphalt pavers with automatic grade control.

If placing NSDB in areas inaccessible to spreaders, spread the NSDB using approved methods.

The Department will test for in place gradation after spreading but before compaction testing according to Supplement 1090.

307.10 Compaction. The Department will measure the compaction according to Supplement 1015.

To determine project compaction requirements, construct one or more test sections according to 1015.07 in Supplement 1015. Compact the test section by using a minimum of two passes for Type NJ, four passes for Type IA, and six passes with the vibratory roller for the Type CE. A pass is defined as one passage of a compacting unit over the entire surface of the layer. Compact the test section until a maximum dry density is achieved.

Use at least the same number of passes and moisture content used to obtain the maximum dry density in the test section for the production area construction. Compact the material immediately after spreading. The Engineermay reduce the minimum passes if the passes are detrimental to compaction.

Compact the production areas to ensure that the average dry density is greater than 95 percent of the average maximum test section dry density. Achieve this density without crushing the aggregate.

If a production lot fails to meet 95 percent of the average maximum test section dry density, recompact it and resubmit it for acceptance. The Engineerwill determine the new average lot density. If the recompacted lot density still fails to meet 95 percent of the average maximum test section density, construct a new test section.

If placing NSDB in areas inaccessible to rollers, compact material using other approved methods.

307.11 Shaping and Finishing. After compacting NSDB, shape the surface to the required cross-section.

If the shaping reduces the density, recompact the section to conform to the original tested density.

Compact and shape the NSDB to produce uniform density and cross-section.

307.12 Limitations on Placing Operations. Do not spread on frozen material. Do not use frozen material.

Do not place NSDB when rain softens the underlying base course or subgrade.

Do not place the NSDB during any weather conditions that would cause its degradation, segregation, or contamination.

307.13 Protection of the Underdrains. Do not allow equipment to crush any part of the underdrain system as a result of the placement or compaction of NSDB. Repair or replace damaged underdrain pipe or system.

Provide a positive connection between the underdrain backfill and the NSDB at all times.

307.14 Protection of the Non-Stabilized Drainage Base. Do not use NSDB for a haul road. Do not use hauling units and other construction vehicles on Type NJ and Type IA. The Contractormay operate hauling units for distances less than 50 feet (15 m) to access the paver on the Type CE. Only use the paving equipment to place the next layer of pavement on Type NJ and Type IA.

When placing the next pavement layer, use equipment to side dump pavement materials onto the Type NJ and Type IA NSDB.

Protect the NSDB from fine material contamination at all times. If the Engineerdetermines that significant displacement, breakup, or contamination of Type CE is occurring, cease operating the hauling units on the Type CE NSDB. The Engineer will not allow hauling units to travel on the Type CE NSDB until the Contractorhas satisfactorily demonstrated that displacement, breakup, or contamination is not expected to recur.

Provide adequate surface and subsurface drainage for the NSDB, base, and subgrade at all times.

If constructing an asphalt concrete pavement on the NSDB, place the first course using a paver mounted on tracks. Allow the first course to cure overnight before placing the succeeding pavement courses. Do not use hauling equipment to operate on the pavement until a minimum of 7 1/2 inches (190 mm) of asphalt concrete has been placed.

307.15 Thickness Tolerances. Ensure that the maximum compacted depth of NSDB is 4 inches (100 mm). Ensure that the final depth complies with the plans.

The thickness tolerance is 1/2 inch (13 mm). Correct thin areas by adding material, grading, and compacting.

307.16 Surface Tolerance. Use templates, slope boards, or other devices to verify surface tolerance.

Ensure that the finished surface is uniform and does not vary more than 1/4 inch (6 mm) from a 10-foot (3 m) straightedge applied to the surface parallel to the centerline of the pavement. Correct low areas by adding material, grading, and compacting.

307.17 Exposure to the Elements. Place the next layer of pavement within 40 days of the construction of NSDB.

The Contractormay construct the NSDB any time that complies with the restrictions specified in 307.12. However, completely cover the NSDB with the next layer of pavement, and place the underdrain system and have it functioning before the atmospheric temperature falls below 35 F (2 C) or by the end of the construction season in any given calendar year.

Remove and replace overlaying pavement, NSDB, base, subgrade, and underdrains damaged by exposure to temperatures below 35 F (2 C) at no expense to the Department.

307.18 Method of Measurement. The Department will measure 4 inch (100 mm) Non-Stabilized Drainage Base, for the type specified, by the number of square yards (square meters) of each computed from the profile grade and typical sections accepted in place.

307.19 Basis of Payment. The Department will not pay for recompaction work if a production lot fails to meet 95 percent of the average maximum test section density. The Department will not pay for the construction of a new test section if the recompacted lot density fails to meet 95 percent of the average maximum test section density. The Department will not pay for repair or replacement of damaged underdrain pipe or system. The Department will not pay for the correction of low areas.

The Department will pay for accepted quantities at the contract prices as follows:

Item unit Description

307 Square Yard 4 inch (100 mm)
(Square Meter) Non-Stabilized Drainage Base, Type NJ

307 Square Yard 4 inch (100 mm)
(Square Meter) Non-Stabilized Drainage Base, Type IA

307 Square Yard 4 inch (100 mm)
(Square Meter) Non-Stabilized Drainage Base, Type CE