303.01 220 SECTION 303 – MINERAL AGGREGATE BASE
303.01 Description ................................ ................................ ................... 220
303.02 Aggregate ................................ ................................ ..................... 220
303.03 Calcium Chloride ................................ ................................ ......... 221
303.04 Reserved ................................ ................................ ....................... 221
303.05 Emulsified Asphalt ................................ ................................ ....... 221
303.06 Equipment ................................ ................................ .................... 221
303.07 General ................................ ................................ ......................... 222
303.08 Mixing ................................ ................................ .......................... 223
303.09 Spreading ................................ ................................ ..................... 224
303.10 Shaping and Compaction ................................ ............................. 225
303.11 Maintenance ................................ ................................ ................. 227
303.12 Thickness Requirements ................................ .............................. 227
303.13 Surface Requirements ................................ ................................ .. 227
303.14 Method of Measurement ................................ .............................. 228
303.15 Basis of Payment ................................ ................................ .......... 229
DESCRIPTION
303.01 Description
This work consists of furnishing and placing one or more courses of aggregates, and additives if required, on a prepared subgrade. Mineral aggregates base shall be Type A or Type B, whichever is shown on the Plans and called for in the bid schedule. Recycled Concrete Aggregate (RCA) may be used as an alternate for Type A or Type B base material. MATERIALS
303.02 Aggregate
Depending upon whether the Plans require Type A or Type B base, provide mineral aggregate meeting 903.05. For Type A base, use aggregate of Grading D. For Type B base, the Contractor may use aggregate of Grading C or D. For RCA, use grading specified in 903.05.C. 303.03 221 The Engineer will accept aggregate for gradation as follows:
1.When the stationary plant method for mixing is used, the Engineer will accept aggregate immediately after or prior to mixing, based on periodic samples taken from the pugmill output or from the belt feeding the pugmill.
2.When two or more materials are blended on the road using mechanical mixers, the Engineer will accept aggregate after mixing and before compaction, based on samples taken from each layer of base material
3.For aggregate that does not require blending, the Engineer will accept aggregate at the aggregate production plant, based on samples taken from stockpiles of plant production immediately before delivery to the road.
303.03 Calcium Chloride
Provide calcium chloride meeting 921.02 for Type 1, Type 2 or calcium chloride liquor .
303.04 Reserved
303.05 Emulsified Asphalt
Use emulsified asphalt of a type allowed for Prime Coat in 401, meeting the test requirements specified in 904.03. EQUIPMENT
303.06 Equipment
Provide a stationary mixing plant, mechanical road mixer , or motor grader, whichever is applicable to the type of work to be performed, as specified in 303.08.
A.Stationary Mixing Plant Provide an approved twin -shaft pugmill capable of producing a constant, uniform mixture. Equip the mixing plant with the following: 303.07 222 1. suitable truck -loading hopper with a gate that will prevent segregation of the material when dumped into the truck;
2.A spray bar, capable of ensuring an even wetting of the aggregate, mounted at the entrance of or above the pugmill;
3.A meter, valve, or other approved type of regulating device to control the flow of water through the spray bar to maintain a uniform moisture content in the mixture;
4.A separate, quick, and automatically operating on -and-off device to shut the water off instantly when the pug mill stops; and
5.Adjustable mechanical feeders for each size material capable of regulating a constant, uniform flow of material.
B.Mechanical Mixer (for Road Mixing ) Provide a pugmill or rotary type mechanical mixer capable of producing a uniform blend of al l materials to the full depth of the course being placed. The mixer may be either self -propelled or trailer -drawn.
C.Compaction Equipment Provide one or more rollers of a type and sufficient weight to obtain the required density and seal the surface of the base course. CONSTRUCTION REQUIREMENTS
303.07 General
Construct Mineral Aggregate Base, Type A, Type B, or RCA in one or more layers, to the compacted thickness shown on the Plans. Prepare the subgrade as specified in 207 or 302, whichever is applicable. Obtain the Engineer’s approval of the subgrade before spreading any mineral aggregate. Subgrade that has been previously checked and approved, but subsequently subjected to freezing conditions or prolonged wet weather, shall be rechecked for approval. Do not spread mineral aggregate on a subgrade that is frozen or contains frost. 303.08 223 Do not haul over any material that has been placed until it has been spread, mixed, shaped and compacted to the requi red density.
303.08 Mixing
A.Mixing Methods Unless otherwise specified, mix the base course material, including an additive if shown on the Plans, by one or more of the following three methods:
1.Stationary Plant Method. Mix the base course material and water in an approved stationary mixing plant as specified in 303.06.A. Add sufficient water during the mixing operation to provide a moisture content satisfactory for compacting. If combining materials to meet the grading requirements, blend the materials, as specified in 903.05, before mixing. Ensure that all material fed into the plant travels the full length of the pugmill.
2.Road Mix Method (Mechanical Mixer). After placing the material for each layer of base course through an aggregate spreader or windrow -sizing device, mix the material usin g approved mechanical mixing machines as specified in 303.06.B. During mixing, add sufficient water to provide a moisture content satisfactory for compacting.
3.Road Mix Method (Motor Grader). After depositing and uniformly spre ading material for each layer of base course, sprinkle it with just enough water to moisten all particles, but without causing segregation of sizes or softening of the subgrade. Immediately after applying water, thoroughly mix the material by windrowing a nd spreading with motor graders until the mixture is uniform throughout. For Mineral Aggregate Base, Type A, use the stationary plant method. For Mineral Aggregate Base, Type B, requiring the blending of two or more materials, use either the stationary plant method or the road mix method (mechanical mixer), except as provided for in 903.05. For Mineral Aggregate Base, Type B, requiring additive, use either stationary plant mixing or road mixing. When using RCA as a replacement for Mineral Aggregate Base, Type A or Type B, use the intended method of mixing for the material listed above. 303.09 224 B. Use of Calcium Chloride If using calcium chloride, incorporate it in either the solid or liquid form, at the approximate rate of 6 pounds per ton of aggregate, noting that: • 6 pounds is equivalent to 1.29 gallons 60 °F 32% solution • 6 pounds is equivalent to 1.02 gallons 60 °F 38% solution For stationary plant mixing, proportion chloride material, in solid form, through a hopper equipped with an approved vibratory feeder and an adjustable opening capable of accurately con trolling the flow of material. Proportion calcium chloride liquor using an approved calibrated meter that has a registering capacity capable of indicating the total amount of liquid used during any single day’s operation. For road mixing, add the chloride material to the aggregate at the point in the mixing operation and in the manner directed by the Engineer.
303.09 Spreading
Spread material as follows according to the mix method used:
A.Stationary Plant Mixing After mixing, transport material to the site for each layer of base while it contains the proper moisture content. Spread the material to the required thickness and cross -section using an approved mechanical spreader.
B.Road Mixing ( Mechanical Mixer) Before mixing, spread material with an approved mechanical spreader that can be adjusted to spread materials in the proper proportions.
C.Road Mixing (Motor Grader) After thoroughly mixing the aggregate and water, spread the base material w hile at optimum moisture content in layers of specified thickness and cross -section using approved motor graders. If the required compacted depth of the base course exceeds 6 inches, construct the base in two or more layers of approximate equal thickness. The maximum compacted thickness of any one layer shall not exceed 6 inches. 303.10 225 In some cases, the Plans may show the base as extending for the full width of the roadbed. In other cases, the edges of the base may be shown as coinciding with the inside edges of the shoulders. In the latter case, place shoulder material to a minimum width of 3 feet before spreading each layer of base material in order to confine the base material and to allow for proper compaction. The Contractor may spread and mix any base ma terial used for constructing detours, for maintenance of traffic, for backfilling rock cuts, and for capping rock fills as specified in 303.09.B.
303.10 Shaping and Compaction
A.Final Shaping Immediately after spreading, shape the base material to the required degree of uniformity and smoothness. Except where using mechanical aggregate spreading equipment to place the base material, use a motor grader to shape each layer before compacting . If the mechanical spreading equipment fails to shape the base material properly, use a motor grader or other approved means to perform final shaping.
B.Compacti on Compact the base material to the required density before any appreciable evaporation of surface moisture occurs. Continuously compact each layer until the minimum density requirement, as specified in 303.10.C.2 , is achieved. The Contractor may use any type of compacting equipmen t provided the required density is attained. If the density requirement does not apply, as provided for in 303.10.C.3 , gradually compact the base material, progressing from the edges of the base to the center, parallel with the centerline of the road. Continue compacting until the base layer has been compacted to its full width as directed by the Engineer. Where lifts of shoulder materials are placed to confine the base material, overlap the initial pass of th e compacting equipment with the shoulder to a width of not less than 12 inches. Construct the surface of each layer so that the aggregates become firmly keyed and a uniform texture is produced. Maintain the surface in this condition until it is covered by the following stage of construction or until final acceptance of the project. Correct irregularities by loosening the material at those places and adding or removing material as required. 303.10 226 Use approved distributors to apply water uniformly over the base materials during compaction in sufficient quantity to allow for proper compaction without causing softening of the underlying subgrade due to excessive water use.
C.Compaction Acceptance
1.Lot Sizes and Testing. For density testing purposes, the Department will divide each completed layer into lots of approximately 10,000 square yards , and will average the results of five density tests performed on each lot. Smaller lots may be considered as directed or approved by the Engineer.
2.Density Requirements
a.Type A Base. The average density of each lot of Type A base, unless otherwise specified, shall be not less than 100% of maximum density as determined according to AASHTO T 99, Method D, with no individual test less th an 97% of maximum density.
b.Type B Base. The average density of each lot of Type B base, unless otherwise specified, shall be not less than 97% of maximum density as determined according to AASHTO T 99, Method D, with no individual test being less than 95 % of maximum density.
c.RCA Base. The average density of each lot of RCA base, unless otherwise specified, shall be not less than 100% of maximum density as determined according to AASHTO T 99, Method D, with no individual test less than 97% of maximum density. The moisture content shall be within plus or minus 3% of the optimum moisture content as determined by Departmental analysis. Mixing of the material with water shall be completed per 303.08. If the specified density is not obtained for either type of base, rework or replace the material to comply with the density requirement.
3.Exclusions. Unless otherwise specified, the density requirements specified in 303.10.C.2 will not apply to: 303.11 227 a. Type A or Type B base construction on projects that do not include the construction of a surface upon the base, or to
b.Projects having a specified total base thickness of less than 4 inches. When the specified density requirements do not apply, the Engineer will consider the desired degree of compaction to have been reached when the surface is tightly bound and shows no undue rutting or displacement under operation of the roller or other equipment. Obtain the Engineer’s approval of the compaction of each layer before placing material for th e next successive layer. Keep placing and compacting areas separate.
303.11 Maintenance
Maintain the completed base in a smooth and uniform condition until it is covered by the following stage of construction or the Project has been completed and accepted. Comply with the requirements of 104.05 regarding maintenan ce and protection.
303.12 Thickness Requirements
Construct the base to the grade and compacted thickness shown on the Plans, with an allowable working tolerance of plus or minus 1/2 inch. The thickness will be measured at such frequency as established by the Department using test holes or other approved methods.
303.13 Surface Requirements
The surface of the finished base shall be in reasonably close conformity to the lines, grades, and cross -sections sho wn on the Plans or established by the Engineer and shall have a satisfactorily smooth riding quality . 303.14 228 COMPENSATION
303.14 Method of Measurement
A.Mineral Aggregate for Mineral Aggregate Base, Type A, Type B, or RCA The Department will measure Mineral Aggregate for Mineral Aggregate Base, Type A, Type B, or RCA, by the ton, in accordance with 109.
B.Water The Department will deduct the weight of total moisture, as determined by dry weights , of the base material at the time of weighing in excess of 3% of optimum moisture content. The Department will not measure or pay for water when mixing is performed in a stationary plant, When road mixing is performed, the Department will measure water added to the material at the direction of the Engineer by the M.G. (1,000 gallons) using calibrated tanks or distributors, or accurate water meters.
C.Calcium Chloride The Department will measure calcium chloride by the ton. The Department will weigh calci um chloride received in liquid form as specified in 109, and will convert the weight of liquid calcium chloride to tons as follows:
1.32% Solution Tons Calcium Chloride =(Total tons of 32% solution) x 0.32 0.94
2.38% Solution Tons Calcium Chloride =(Total tons of 38% solution) x 0.38 0.94 303.15 229 The Department will consider calcium chloride liquor used in a solution of 32% or more, but less than 38%, as a 32% solution. The Depar tment will consider a solution of 38% or greater as a 38% solution.
303.15 Basis of Payment
A.The Department will pay for accepted quantities at the contract prices as follows: Item Pay Unit Mineral Aggregate, Type ____ Base Ton Calcium Chloride Ton Water MG The Department will pay for the work required to prepare the subgrade in accordance with 303.07 as provided for in the applicable Section or Subsection under which the work is performed.
B.Adjustments Specific Gravity. In cases where the Bulk SSD specific gravity of the mineral aggregate exceeds 2.8 5, the Department will adjust the tonnage of mineral aggregate for payment by multiplying the tonnage of mineral aggregate used by a specific gravity of 2.8 5 and dividing by the higher specific gravity. 304.01 230 SECTION 304 – SOIL-CEMENT BASE
304.01 Description ................................ ................................ ................... 230
304.02 Materials ................................ ................................ ...................... 230
304.03 Equipment ................................ ................................ .................... 231
304.04 Limitations ................................ ................................ ................... 231
304.05 Preparing the Existing Subgrade ................................ .................. 232
304.06 Pulverizing ................................ ................................ ................... 232
304.07 Cement Application, Mixing, and Spreading ............................... 232
304.08 Compaction ................................ ................................ .................. 233
304.09 Finishing ................................ ................................ ...................... 234
304.10 Construction Joints ................................ ................................ ....... 234
304.11 Thickness and Surface Tolerances ................................ ............... 234
304.12 Curing ................................ ................................ .......................... 234
304.13 Reconstruction and Replacement ................................ ................. 235
304.14 Traffic ................................ ................................ .......................... 235
304.15 Maintenance ................................ ................................ ................. 235
304.16 Method of Measurement ................................ .............................. 236
304.17 Basis of Payment ................................ ................................ .......... 236
DESCRIPTION
304.01 Description
This work consists of mixing in -place or select soil with Portland cement, and moistening and compacting the soil -cement mixture in one or more courses. MATERIALS
304.02 Materials
Provide materials as specified in: Portland Cement, Type I ................................ ........................ 901.01 Portland-Pozzolan Cement, Type IP ................................ ...... 901.01
Source: Tennessee Standard Specifications for Road and Bridge Construction, 2021 Edition. Pages 229–238 of 1,072.