DESCRIPTION 247-1.1 Construct a foundation course composed of flexible base

MATERIALS

Furnish uncontaminated materials of uniform quality that meet the requirements of the plans and specifications. Notify the Owner’s Authorized Representative (OAR) of the proposed material sources and of changes to material sources. The OAR may sample and test project materials at any time before compaction throughout the duration of the project to assure specification compliance. Use Tex-100-E material definitions.

247-2.1 Aggregate. Furnish aggregate of the type and grade shown on the plans and meeting the requirements of Table 1. Each source must meet Table 1 requirements for liquid limit, plasticity index, and wet ball mill for the grade specified. Do not use additives, such as but not limited to lime, cement, or fly ash to modify aggregates to meet the requirements of Table 1 unless shown on the plans.

Table 1 Plasticity index, Min¹ As shown on

the plans

a. Tolerances. The OAR may accept material if no more than 1 of the 5 most recent gradation tests has an individual sieve outside the specified limits of the gradation.

When target grading is required by the plans, no single failing test may exceed the master grading by more than 5 percentage points on sieves No. 4 and larger or 3 percentage points on sieves smaller than No. 4.

The OAR may accept material if no more than 1 of the 5 most recent plasticity index tests is outside the specified limit. No single failing test may exceed the allowable limit by more than 2 points.

b. Material Types. Do not use fillers or binders unless approved. Furnish the type specified on the plans in accordance with the following:

i. Type A. Crushed stone produced and graded from oversize quarried aggregate that originates from a single, naturally occurring source. Do not use gravel or multiple sources.

ii. Type B. Crushed or uncrushed gravel. Blending of 2 or more sources is allowed.

iii. Type C. Crushed gravel with a minimum of 60% of the particles retained on a No. 4 sieve with 2 or more crushed faces as determined by Tex 460 A, Part I. Blending of 2 or more sources is allowed.

iv. Type D. Type A material or crushed concrete. Crushed concrete containing gravel will be considered Type D material. Crushed concrete must meet the requirements in Section 247-2.1(c), “Recycled Material (Including Crushed Concrete) Requirements,” and be managed in a way to provide for uniform quality. The OAR may require separate dedicated stockpiles in order to verify compliance.

247-2.2 Water. Furnish water free of industrial wastes and other objectionable matter.

247-2.3 Material Sources. Expose the vertical faces of all strata of material proposed for use when non-commercial sources are used. Secure and process the material by successive vertical cuts extending through all exposed strata, when directed.

247-2.4 Geogrid Base Reinforcement. Geogrid base reinforcement must meet the material requirements as specified in Item X-5022, “Geogrid Base Reinforcement”. Geogrid base reinforcement must be used under flexible base course. Geogrid base reinforcement must extend beyond the bottom of the flexible base material layer a minimum of six (6) inches.

EQUIPMENT

247-3.1 General Equipment Requirements. All equipment necessary to mix, transport, place, compact, and finish the flexible base course must be furnished by the Contractor. The Contractor must provide written

Min compressive strength, psi

Tex-117-E As shown on

the plans

lateral pressure 0 psi 35 – –

lateral pressure 3 psi – – 90

lateral pressure 15 psi 175 – 175

1. Determine plastic index in accordance with Tex-107-E (linear shrinkage) when liquid limit is unattainable as defined in Tex-104-E.

2. Grade 4 may be further designated as Grade 4A, Grade 4B, etc.

certification to the OAR that all equipment meets the requirements for this specification. The equipment must be inspected by the OAR at the job site prior to the start of construction operations.

247-3.2 Hauling Equipment. The flexible base materials must be transported to the job site in hauling equipment having beds that are smooth, clean, and tight. Truck bed covers must be provided and used to protect the flexible base materials from rain during transport.

247-3.3 Placing Equipment. Recycled concrete aggregate must be placed using a mechanical spreader, motor grader or machine capable of receiving, spreading, and shaping the material into a uniform layer or lift without segregation. The placing equipment must be equipped with a strike off plate that can be adjusted to the layer thickness or have grade control. The placing equipment must have two end gates or cut off plates, so that the recycled concrete aggregate may be spread up to a lane width.

247-3.4 Compaction Equipment. Materials must be compacted using one or a combination of the following pieces of equipment: steel-wheeled roller; vibratory roller; pneumatic-tire roller; and/or hand-operated power tampers (for areas inaccessible to rollers).

247-3.5 Finishing Equipment. Trimming of the compacted recycled concrete aggregate to meet surface requirements must be accomplished using a motor grader or self-propelled grader or trimming machine, with a mold board cutting edge of 12 feet minimum width automatically controlled by sensors in conjunction with an independent grade control from a taut stringline or laser grade-controlled grading device. If stringline is used the stringline will be required on both sides of the sensor controls for all lanes.

CONSTRUCTION METHODS

247-4.1 Construct each layer uniformly, free of loose or segregated areas, and with the required density and moisture content. Provide a smooth surface that conforms to the typical sections, lines, and grades shown on the plans or as directed.

Stockpile base material temporarily at an approved location before delivery to the roadway. Build stockpiles in layers no greater than 2 ft. thick. Stockpiles must have a total height between 10 and 16 ft. unless otherwise approved. After construction and acceptance of the stockpile, loading from the stockpile for delivery is allowed. Load by making successive vertical cuts through the entire depth of the stockpile.

Do not add or remove material from temporary stockpiles that require sampling and testing before delivery unless otherwise approved. Charges for additional sampling and testing required as a result of adding or removing material will be deducted from the Contractor’s estimates.

Haul approved flexible base in clean trucks. Deliver the required quantity to each 100 ft. station or designated stockpile site as shown on the plans. Prepare stockpile sites as directed. When delivery is to the 100 ft. station, manipulate in accordance with the applicable Items.

247-4.2 Preparation of Subgrade. Shape the subgrade or existing base to conform to the typical sections shown on the plans or as directed.

Proof roll the roadbed in accordance with Item P-152, “Excavation, Subgrade, and Embankment,” before pulverizing or scarifying when shown on the plans or directed. Correct soft spots as directed. Proof rolling will not be measured or paid separately. The work performed, materials furnished, equipment, labor, tools, and incidentals will not be measured or paid for directly but will be subsidiary to pertinent Items.

The underlying course must be checked by the OAR before placing and spreading operations are started.

Prior to constructing the base course, clean the underlying course or subgrade of all foreign substances. The surface of the underlying course or subgrade must meet specified compaction and surface tolerances in accordance with the relevant spec.

247-4.3 Placing. Spread and shape flexible base into a uniform layer with an approved spreader the same day as delivered unless otherwise approved. Construct layers to the thickness shown on the plans. Maintain the shape of the course. Control dust by sprinkling, as directed. Correct or replace segregated areas as directed, at no additional expense to the Owner.

Place successive base courses and finish courses using the same construction methods required for the first course.

The flexible base material must be placed on the moistened underlying subgrade or base in layers of uniform thickness with a motor grader or approved mechanical spreader.

Where geotextile fabric is required to be placed under the recycled concrete base it must be placed over the subgrade in accordance with the manufacturer's recommendations. In areas of undercut and backfill, the fabric must be placed over the backfill at the top of subgrade level. Dumping of the material directly on the fabric will not be allowed. Only construction equipment required for the placement of the recycled concrete base will be allowed on the fabric prior to the placement of the recycled concrete base. Fabric which is damaged during installation or subsequent placement of recycled concrete base must be repaired or replaced by the Contractor at his own expense to the satisfaction of the OAR.

The maximum depth of a compacted layer will be 12 inches. If the total depth of the compacted material is more than 12 inches, it must be constructed in two or more layers. In multi-layer construction, the material must be placed in approximately equal-depth layers. The material, as spread, must be of uniform gradation with no pockets of fine or coarse materials. The flexible base course, unless otherwise permitted by the OAR, must not be spread more than 2,000 square yards in advance of the rolling. Any necessary sprinkling must be kept within this limit. No material will be placed in snow or on a soft, muddy, or frozen course.

The previously constructed layer must be cleaned of loose and foreign material prior to placing the next layer. The surface of the compacted material must be kept moist until covered with the next layer.

Adjustments in placing procedures or equipment must be made to obtain grades, to minimize segregation grading, to adjust the water content, and to ensure an acceptable recycled concrete base course.

Weather limitations. Material shall not be placed unless the ambient air temperature is at least 40°F (4°C) and rising. Work on flexible base course may not be conducted when the subgrade or subbase is wet or frozen or the base material contains frozen material. When the temperature falls below 35°F, the Contractor must protect all completed areas against detrimental effects of freezing. The Contractor must repair any areas damaged by freezing, rainfall, or other weather conditions.

247-4.4 Compaction. Compact using density control unless otherwise shown on the plans. Multiple lifts are permitted when shown on the plans or approved. Bring each layer to the moisture content directed.

When necessary, sprinkle the material with water to bring the material in accordance with P-152,

“Excavation, Subgrade, and Embankment.”

Begin rolling longitudinally at the sides and proceed towards the center, overlapping on successive trips by at least 1/2 the width of the roller unit. Begin rolling at the low side and progress toward the high side on superelevated curves. Offset alternate trips of the roller. Operate rollers at a speed between 2 and 6 mph as directed.

Rework, recompact, and refinish material that fails to meet or that loses required moisture, density, stability, or finish requirements before the next course is placed or the project is accepted. Continue work until specification requirements are met. Perform the work at no additional expense to the Owner.

Before final acceptance, the OAR will select the locations of tests and measure the flexible base depth in accordance with Tex 140 E. Correct areas deficient by more than 1/2 in. in thickness by scarifying, adding material as required, reshaping, recompacting, and refinishing at the Contractor’s expense.

a. Ordinary Compaction. Roll with approved compaction equipment as directed. Correct irregularities, depressions, and weak spots immediately by scarifying the areas affected, adding or removing approved material as required, reshaping, and recompacting.

b. Density Control. Compact to at least 100% of the maximum dry density determined by Tex-113-E, unless otherwise shown on the plans. Maintain moisture during compaction within ±2 percentage points of the optimum moisture content as determined by Tex-113-E. Measure the moisture content of the material in accordance with Tex 115-E or Tex-103-E during compaction daily and report the results the same day to the OAR, unless otherwise shown on the plans or directed. Do not achieve density by drying the material after compaction.

The OAR will determine roadway density and moisture content of completed sections in accordance with Tex 115 E. The OAR may accept the section if no more than 1 of the 5 most recent density tests is below the specified density and the failing test is no more than 3 pcf below the specified density.

247-4.4 Finishing. After completing compaction, clip, skin, or tight-blade the surface with a maintainer or subgrade trimmer to a depth of approximately 1/4 in. Remove loosened material and dispose of it at an approved location. Seal the clipped surface immediately by rolling with a pneumatic tire roller until a smooth surface is attained. Add small increments of water as needed during rolling. Shape and maintain the course and surface in conformity with the typical sections, lines, and grades as shown on the plans or as directed.

Correct grade deviations greater than 1/4 in. in 16 feet measured longitudinally or greater than 1/4 in. over the entire width of the cross-section in areas where surfacing is to be placed. Correct by loosening and adding, or removing material. Reshape and re-compact in accordance with Section 247-4.3., “Compaction.”

a. Thickness. Thickness verifications will be determined by survey on a survey grid not exceeding 50-foot by 50-foot. An evaluation of each surface will be performed by a licensed surveyor at the direction of the OAR. The OAR will pay for the costs of surveying the initial level runs. Any subsequent level runs required to verify the compliance of any reworked areas will be at the Contractor’s expense and will be deducted from payments due to the Contractor for work performed. The thickness of the base course shall be within +0 and -1/2 inch of the specified thickness as determined by depth tests taken by the Contractor in the presence of the OAR for each area. Where the thickness is deficient by more than 1/2-inch, the Contractor shall correct such areas at no additional cost by scarifying to a depth of at least 3 inches, adding new material of proper gradation, and the material shall be blended and recompacted to grade. The Contractor shall replace, at his expense, base material where depth tests have been taken.

If the survey shows a thickness deficiency, the Contractor may elect to verify depths via measurement of core holes, completed at the Contractor’s expense. The resulting core holes must be filled by the Contractor with CTB or non-shrink grout.

247-4.5 Curing. Cure the finished section until the moisture content is at least 2 percentage points below optimum or as directed before applying the next successive course or prime coat.

247-4.6 Materials not Accepted for Use. Any materials not accepted by the OAR for use in the project or any excess materials not used by the Contractor must be removed and disposed of off the Airport property in accordance with local laws and regulations, unless otherwise noted. No material may be wasted on the Airport site unless approved by the Owner. This is subsidiary to the various bid items of the project.

MEASUREMENT AND PAYMENT

247-5.1 See Section 01 22 00, Measurement and Payment, for description of pay items related to this scope of work.

REFERENCES

The publications listed below form a part of this specification to the extent referenced. The publications are referred to within the text by the basic designation only.

Texas Department of Transportation

DMS 11000 Evaluating and Using Nonhazardous Recyclable Materials Guidelines Materials Producer List (MPL)

Standard Specifications for Construction and Maintenance of Highways, Streets and Bridges Tex-100-E Surveying and Sampling Soils for Highways

Tex-103-E Determining Moisture Content in Soil Materials Tex-104-E Determining Liquid Limits of Soils

Tex-106-E Calculating the Plasticity Index of Soils Tex-107-E Determining the Bar Linear Shrinkage of Soils Tex-110-E Particle Size Analysis of Soils

Tex-113-E Laboratory Compaction Characteristics and Moisture-Density Relationship of Base Materials

Tex-115-E Field Method for Determining In-Place Density of Soils and Base Materials

Tex-116-E Ball Mill Method for Determining the Disintegration of Flexible Base Material

Tex-117-E Triaxial Compression for Disturbed Soils and Base Materials Tex-140-E Measuring Thickness of Pavement Layer

Tex-145-E Determining Sulfate Content in Soils - Colorimetric Method

Tex-400-A Sampling Flexible Base, Stone, Gravel, Sand, and Mineral Aggregates Tex-406-A Material Finer than 75 micrometer (No. 200) Sieve in Mineral

Aggregates (Decantation Test For Concrete Aggregates) Tex-460-A Determining Crushed Face Particle Count

Tex-1001-S Operating Inertial Profilers and Evaluating Pavement Profiles