302Class II Base Course

302.01 DESCRIPTION. Furnish and place Class II roadway and

shoulder base course on a prepared surface in accordance with these specifications, in conformity with the lines, grades, thickness, and typical sections shown on the plans or established. Control the selection, placement, mixing and compaction of materials so that the completed base course is uniform and conforms to plan dimensions and other acceptance requirements. Quality assurance requirements shall be as specified in the latest edition of the Department’ s publication titled Application of Quality Assurance Specifications for Embankment and Base Course. When not specified, any of the following types may be used:

302.02 MATERIALS. Materials shall comply with the following

sections or subsections and requirements. Geotextile Fabric 203.11 & Section 1019 Asphalt Concrete Section 502 Portland Cement Concrete Section 901 Portland Cement 1001.01 Blended Hydraulic Cement 1001.02 Asphalt Materials Section 1002 Stone 1003.01 & 1003.03.1 Recycled Portland Cement Concrete 1003.01 & 1003.03.2 Blended Calcium Sulfate 1003.01 & Error! Reference source not found. Water 1018.01

302.02.1 Soils for Soil Cement: Soils for soil cement base course

shall consist of materials that will stabilize with cement in accordance with DOTD TR 432. Such materials are those soils classified as A-1-a, A-1-b, A-2-4, A-2-6, A-4, and A-6 in accordance with DOTD TR 423. Do not use soil with a Liquid Limit greater than 35, a Plasticity Index (PI) greater than 15, or an organic content greater than 2 percent. Determine Liquid Limit and Plasticity Index in accordance with DOTD TR 428. Determine organic content in accordance with DOTD TR 413. Do not use soil with over 79 percent sand or 60 percent silt when tested in accordance with DOTD TR 407. Soils may be blended to adjust the percentages of sand or silt to meet specification requirements; however, in- place blending is not allowed. Do not blend or treat soils that do not meet Liquid Limit or PI requirements to reduce Liquid Limit or PI. Do not use topsoil. Obtain the material to be stabilized from outside right-of-way limits except as provided in 106.02.3. The engineer will take samples from the roadway or stockpile in accordance with the Material Sampling Manual. The District Laboratory Engineer will approve materials prior to blending and the final product. Acceptance of soils with organic contents between 2 to 5 percent may be allowed based on determination of increased cement percentages in accordance with DOTD TR 432 Method B or C, whichever is applicable, using the design compressive strength criteria listed for stabilization. Maximum cement rate allowed will be 14 percent by volume. Perform the laboratory testing specified above at no expense to the Department . The laboratory used must be approved by the Materials Engineer Administrator. Take samples in the presence of the engineer in accordance with the Material Sampling Manual. Obtain sufficient material to provide the District laboratory with approximately 200 pounds of the base material to be treated for verification testing. The engineer will take immediate possession of the verification samples. Also provide approximately 10 pounds of the selected cementitious material to the District laboratory. Provide materials for verification testing at no cost to the Department. Submit all design data used to determine the recommended cement rate to the District Laboratory Engineer for approval. Prior to approval of the design, the District Laboratory will perform verification testing. Verification testing by the District Laboratory will consist of molding, curing and testing a minimum of three specimens in accordance with TR 432, at the percentage of cementitious material and at the optimum moisture determined by the contractor’s laboratory. The recommended cement rate will be considered verified if test results indicate that the minimum strength criteria have been met and that the optimum moisture are within 2 percent of that submitted by the contractor. Normal testing time for verification testing may require up to 21 calendar days. Do not begin construction operations until the design is approved.

302.02.2 Portland Cement: Use Type I or II portland cement. The

quantity of cement used shall be supported by proof of delivery.

302.02.3 Blended Hydraulic Cement: The cement shall be Type

IP. The quantity of cement used shall be supported by proof of delivery.

302.02.4 Asphalt Concrete Base Course: The material

requirements for asphalt concrete base course shall be as described in Section 502. The top half of the base thickness shall be asphalt concrete and the remaining thickness shall be the same type and construction as the top layer of embankment, treated layer, or subgrade. Do not place raw, untreated material between a treated layer and the asphalt concrete.

302.02.5 Blended Calcium Sulfate: Take gradation samples in

accordance with 1003.03.3 from the dedicated stockpiles at the point of material origin.EQUIPMENT. Obtain approval of equipment prior to use. When using in-place mixing, the equipment shall conform to 303.03. When using central mixing, the equipment shall conform to 301.03.1. Compaction equipment shall conform to 301.03.1.5.

302.04 GENERAL CONSTRUCTION REQUIREMENTS. Place base

course material on a subgrade prepared in accordance with Section 203, Section 304, Section 305, Section 306 as specified. Construct asphalt concrete base course in accordance with Section 502. Do not use blended calcium sulfate in areas needed to facilitate traffic control. Do not place blended calcium sulfate within 10 feet of metal drainage structures. The contractor will be allowed to substitute any untreated Class II base course material listed in 302.01. Finished lift thickness shall be 9 inches maximum. The Department may allow single lift construction for depths exceeding 9 inches and up to 12 inches based on a rolling pattern that obtains the required density. Use a Class D geotextile separator fabric if an aggregate base course is to be placed on untreated or lime-treated soils.

302.05 Mixing.

302.05.1 Soil Cement: Combine soil with cement and water by in-

place mixing or in a central plant and shape on the subgrade. When in- place mixing is done, spread and mix the cement prior to adding any more water. A minimum of 70 percent of the pulverized soil, as determined by DOTD TR 431, shall pass the No. 4 sieve after mixing. Determine the optimum moisture of the mixture in accordance with DOTD TR 415 or TR 418. The percentage of moisture in the mixture, by dry weight, shall not vary from the optimum moisture by more than ±2.0 percent at the time of compaction when tested in accordance with DOTD TR 403.

302.05.1 1 In-Place Mixing: Samples to determine optimum

moisture and maximum dry density will be taken by the project engineer. Determine maximum dry density in accordance with DOTD TR 415 or TR 418 and in-place density in accordance with DOTD TR 401. After placement of soil and prior to mixing with cement, shape the soil to required section and compact to at least 93.0 percent of maximum dry density at the required grade. From materials sampled in -place on the project, t he engineer will determine the percentage of cement in accordance with DOTD TR 432 prior to mixing. Depending on the type of cement and soil to be used, normal testing time to determine required cement content may require 21 calendar days. Add water as needed to bring the moisture content of the mixture within the tolerance and uniformly mix with the materials. During the mixing process, add water only through the spray bar of the in-place mixer which is adjusted to provide uniform coverage across the completed width of the roadway for the full depth of the base. Do not allow wet streaks or spots. The method of cement distribution shall be such that the amount of cement used can be readily determined. Determine the spread rate of cement in accordance with DOTD TR 436. When the moisture content is not within ±2.0 percent of optimum, discontinue operations and do not resume until the moisture content is controlled within this tolerance. Do not place and pulverize more than one transport until moisture content is within ±2.0 percent of optimum.

302.05.1 2 Central Plant Mixing: Mixing in a central mix plant

shall conform to Section 301. When using central plant mixing, a reduction of 1.0 percent in the volume of cement required will be permitted.

302.05.2 Crushed Stone and Recycled Portland Cement

Concrete: Do not allow crushed stone or recycled portland cement concrete base courses to segregate during construction. Take gradation samples in accordance with 1003.03 from the dedicated stockpiles at the point of material origin.

302.05.3 Blended Calcium Sulfate: Do not use for crossovers,

drives, or in areas needed to facilitate traffic control. In lieu of blended calcium sulfate, substitute any untreated Class II base course material listed in 302.01. Do not place blended calcium sulfate within 10 feet of metal drainage structures. Use approved backfill material in Section 701.

302.06 TRANSPORTING AND PLACING ON SUBGRADE. Use

only transportation and spreading methods that do not damage the subgrade. Place and spread sufficient base course material to obtain required width and compacted thickness within the tolerances set forth in

302.12 Do not allow subgrade material to contaminate the base course.

Any contamination will require retesting and correction of deficiencies. Do not place, spread, or mix base course material on portland cement concrete or asphalt concrete pavements. Do not allow base course construction operations to damage adjacent pavement surfaces, edges and joints. Add water or use other suitable means to prevent dust during the transporting and placing of materials.

302.07 Compacting and Finishing.

302.07.1 General: The finished base course shall have a smooth,

uniform, closely knit surface, free from ridges, waves, laminations or loose material. Thoroughly roll the surface and finish to grade. The cross-slope shall not vary by more than ±0.003 foot/foot. Density requirement shall be in accordance with 302.12. Do not damage the subgrade layer during compaction operations.

302.07.2 Soil Cement: When using central plant mixing, compact

the material and finish in accordance with 301.10, except that the automatic grade machine will not be required. When using in-place mixing, compact the material and finish in accordance with 303.06. Begin mixing operations within one hour of placement. Complete compaction and finishing operations within three hours after initial mixing of cement with base course materials. Upon expiration of the three -hour period after initial mixing, only intermediate finishing (tight blading) of the base course surface will be allowed. Dispose of excess bladed material. Do not drift bladed material along the base. Use stabilized material in the base course except for that small amount necessary for tight blading. Excessive blading, exceeding 10 percent of the base thickness, to achieve plan depth will not be allowed. Complete operations, including tight blading, within 24 hours of mixing. The finished base course shall have a smooth, uniform, closely-knit surface, free from ridges, waves, laminations, or loose materials. Do not spread cement within 2 hours of sunset, unless otherwise approved by the project engineer.

302.07.3 Crushed Stone and Recycled Portland Cement

Concrete: Compact these materials using an approved sheepsfoot-type roller and finish-roll with an approved pneumatic tire roller or a smooth steel wheel roller. Keep the surface uniformly moist during compaction and final finishing.

302.07.4 Asphalt Concrete: Compact and finish asphalt concrete

in accordance with Section 502. The soil layer shall be compacted and finished in accordance with the top layer of embankment or subgrade.

302.07.5 Blended Calcium Sulfate: During placement of blended

calcium sulfate, the percentage of moisture in the mixture, by dry weight, shall not vary from the optimum moisture by more than ±2.0 percent. After application of water, allow the moisture to reach equilibrium in the base before applying rolling techniques. Roll blended calcium sulfate to the edge of the embankment or subgrade. Compact each layer to at least 95 percent of maximum dry density. Determine optimum moisture and maximum density in accordance with DOTD TR 418 Method G modified to include a maximum drying temperature of 140°F. Proof roll by using a load of 25 tons in a 12 to 14 cubic yard tandem dump truck with ten wheels or approved loaded truck determined by the project engineer. Proof rolling shall be a minimum of 5 passes in each direction at the same locations and at a maximum vehicle speed of 3 mph. Test all blended calcium sulfate base by proof rolling immediately prior to placement of surfacing material, including asphalt binder. Correct any irregularities or soft spots prior to placement of the surfacing material. Any rain event on the project site between the proof rolling and placement of the surfacing will require an additional proof rolling as noted above.

302.08 Quality Control of Roadway Operations.

Control the selection, placement, compaction, cement spread, mixing, moisture content, density, thickness, width, surface finish, cross-slope, and grade to produce a completed base course that is uniform and conforms to plan dimensions and other acceptance requirements as provided herein. Control operations to prevent contamination, segregation, soft spots, wet spots, laminations, and other deficiencies. Perform tests necessary to adequately control the work.

302.09 Protection and Curing.

302.09.1 Soil Cement: Upon completion of intermediate finishing,

immediately protect the base course against drying by applying an asphalt curing membrane in accordance with Section 506. Place asphalt curing membrane on the same day as treatment. Maintain complete coverage of the curing membrane from the initial application until the placement of the next course. When allowing traffic, including construction equipment, on the base course, place at least the first lift of surfacing within 30 calendar days unless otherwise directed.

302.09.2 Crushed Stone, Recycled Portland Cement

Concrete, Soil Layer Under Asphalt Concrete, and Blended Calcium Sulfate: Cover the base course with asphalt prime coat in accordance with Section 505 as soon as practical to avoid water infiltration due to rainfall. Maintain complete coverage of asphalt prime coat from the initial application until the placement of the next course.

302.10 MAINTENANCE OF BASE COURSE. Protect the base course

from damage from public traffic or the contractor’s operations and satisfactorily maintain the base course, including the asphalt curing membrane or prime coat. Repair damaged base course at no direct pay. When requiring patching of the base course, in addition to removing damaged or unsound base course, remove a sufficient width and depth of sound base course to ensure satisfactory placement of patching material. The engineer’s approval of the type of patching material will be required before use. Patching or other base course repair shall restore a uniform surface, shall conform to the requirements of the material being used, and shall be completed before paving operations begin. Patch any failures detected during paving. Do not allow public traffic or construction traffic on the completed base course during the 72 -hour curing period. If conditions permit, route both public traffic and construction traffic off the completed base course onto shoulders or other suitable areas during the 72-hour curing period. Traffic may be permitted on the base course during the curing period if conditions warrant and approved by the engineer. When permitting traffic to use the completed base course subsequent to the 72-hour curing period and prior to construction of the surface course, further protect the base by additional applications of asphalt curing membrane or prime coat in accordance with

301.12 at no direct pay.

Prior to surface course construction, correct deficiencies and weak spots, clean the base course surface, repair any damages caused by traffic, and keep the surface true to grade and cross section at no direct pay. Apply and maintain additional asphalt curing membrane or prime coat as directed at no direct pay. When surfacing with asphalt concrete, place the first lift of surfacing within 30 calendar days.

302.11 WEATHER LIMITATIONS. Do not construct base course when

the subgrade or stockpiles are frozen, when raining, when the ambient air temperature is below 35°F, in the case of cement treated bases, or the temperature forecasted by the U.S. Weather Service is to be 25°f or less within the 24-hour period following placement.

302.12 ACCEPTANCE REQUIREMENTS. Soils and aggregates will

be sampled for acceptance by the Department in accordance with the Materials Sampling Manual. For central plant mixing, determine the cement content in accordance with 301.16. For in-place mixing, determine the cement content in accordance with 302.05. Test the moisture content of the soil cement or cement treated mixtures for conformance to optimum moisture content in accordance with DOTD TR 403. Test the pulverization of the soil cement or cement treated mixtures in accordance with DOTD TR 431. At least 70 percent shall pass the No. 4 sieve. Check base course, except asphalt concrete, for acceptance in increments of 1000 linear feet per roadway or 2000 linear feet per shoulder constructed separately. Asphalt concrete acceptance will be in accordance with Section 502.

302.12.1 Density Requirements: Upon completion of compaction

operations, determine base course in-place density, except asphalt concrete, in accordance with DOTD TR 401. Determine density requirements for asphalt concrete base course in accordance with Section 502. The density requirements for Class II ba se course materials other than asphalt concrete shall be a minimum of 95.0 percent maximum dry density in accordance with DOTD TR 418.

302.12.1 1 Soil Cement and Treated Layer Under Asphalt

Concrete: When the density test value for the section falls below 95.0 percent, a payment adjustment will be applied in accordance with Table 302-1 as follows. Table 302-1 Density Acceptance and Payment Schedule Density Test Value (percent) Percent of Contract Unit Price 95.0 & Above 100 94.0 to 94.9 90 93.0 to 93.9 75 Below 93.0 50 or Remove 1 1 At the option of the Chief Engineer.

302.12.1 2 Crushed Stone, Recycled Portland Cement

Concrete, Blended Calcium Sulfate, and Soil Layer under Asphalt Concrete Base Course: When any test value is less than the required density, continue compaction until obtaining the specified density. The acceptance requirements for blended calcium sulfate base course shall be the same as stone base course with the following modifications. Upon completion of compaction operations, determine the density in accordance with DOTD TR 401 except that all moisture content determinations for density calculations shall be conducted by oven drying the material for 24 hours at 140°F. A forced draft type oven capable of maintaining the temperature shall be provided by the contractor for field moisture content determination for density control.

302.12.2 Thickness Requirements: Determine the thickness of

the completed base course in accordance with DOTD TR 602. Do not allow the completed base course to vary from plan thickness in excess of the tolerances in Table 302-2 below. Correct base course thickness deficiencies in excess of these tolerances at no direct pay. Table 302-2 Base Course Thickness Tolerance (All Bases Except Asphalt Concrete) Under-Thickness, Inches (Stabilized & Treated Bases) Over-Thickness, Inches 3/4 11/2 When using crushed stone base or recycled concrete base over soil cement base, the individual base layer tolerances shall be in accordance with Table 302-2, and the total base course under-thickness shall not exceed 1 inch. Any failing area will be isolated for purposes of correction. Determine asphalt concrete base thickness in accordance with Section 502. When using central plant mixing, over-thickness may be waived at no direct pay.

302.12.2 1 Soil Cement, and Treated Layer Under Asphalt

Concrete: When not permitting grade adjustments, correct under- thickness deficiencies in excess of tolerance by removing and replacing the full depth of base course in deficient areas with one of the following materials:

302.12.2 2 Crushed Stone, Blended Calcium Sulfate, and

Recycled Portland Cement Concrete: When allowing grade adjustments, correct under-thickness in excess of 3/4 inch to plan thickness by furnishing, placing, reworking, shaping, and compacting additional base course material as required. When not allowing grade adjustments, remove the material and replace at no direct pay.

302.12.2 3 Asphalt Concrete Base Course: When not

allowing grade adjustments, correct under-thickness in excess of the tolerances given in 502.12 to plan thickness by removing and replacing the full depth of base course. When allowing grade adjustments, correct under-thickness in excess of the tolerances given in 502.12 to plan thickness by placing and compacting an 11/4-inch thick minimum supplemental layer of asphalt concrete complying with Section 502 at no direct pay.

302.12.3 Width Requirements: Determine the width of the

completed base course in accordance with DOTD TR 602. Do not allow roadway base course width to vary from plan width in excess of +6 inches. Do not allow shoulder base course width to vary from plan width in excess of +3 inches. No under-widths are allowed for shoulder or roadway bases. When the base course for both roadway and shoulders are constructed at the same time, the 6-inch tolerance will be applied. Correct base course width deficiencies in excess of the above tolerances as follows at no expense to the Department:

302.12.3 1 Soil Cement and Asphalt Concrete Base

Course:

302.12.3 1.1 Over-Width: Over-widths of asphalt concrete

and treated base courses mixed in a central plant may be waived at no additional cost to the Department. When not allowing grade adjustments, remove the full depth and width of base course in areas having over-widths in excess of the foregoing tolerances and replace to the plan width with one of the following materials:

302.12.3 1.2 Under-Width: Correct under-widths of base

course in excess of the foregoing tolerances to plan width and thickness by furnishing and placing additional materials; however, the width of widening materials shall be not less than 12 inches. When approved, corrections may be made by restabilizing the existing material in accordance with this section, and the cement content may be reduced from design contents with approval of the District Laboratory Engineer. Materials for widening deficient base course may be asphalt concrete complying with Section 502 or concrete complying with Section 901.

302.12.3 2 Crushed Stone, Blended Calcium Sulfate, and

Recycled Portland Cement Concrete: Over-widths will be waived at no additional cost to the Department. Correct under-widths in excess of the foregoing tolerances to plan widths by furnishing, placing, reworking, shaping, and compacting additional base course material as required.

302.12.4 Grade and Cross-Slope: The finished grade shall be

within ±1/2 inch of the established grade. Do not allow the cross-slope to vary by more than ±0.003 foot/foot.

302.12.5 Correction Deficiencies: Correct deficiencies in surface

finish, cross-slope, grade, contamination, segregation, soft spots, wet spots, laminations, and other deficiencies at no direct pay. Correct deficiencies by removing and replacing or as directed.

302.13 MEASUREMENT. The quantities of Class II base course for

payment will be the design volumes or areas specified in the plans and adjustments thereto. Design quantities are based on the horizontal dimensions and compacted thickness of the completed base course shown on the plans. Design quantities will be adjusted if the engineer makes changes to adjust to field conditions, if plan errors are proven, or if design changes are necessary. Geotextile fabric used beneath the base course will not be measured for payment.

302.14 PAYMENT. Payment for Class II base course will be made at the

contract unit price, adjusted as specified in 302.12 and the following provisions, which includes furnishing and placing required base course materials, portland cement, blended hydraulic cement, water, asphalt curing membrane, and prime coat. Any payment adjustment in asphalt concrete shall be in accordance with Section 502 and shall apply to the cubic yard total quantity of base course when payment is by cubic yard. For other materials, when making payment adjustments for more than one deficiency, they shall be cumulative. Payment for geotextile fabric will be included in the contract unit price for base course. Payment will be made under: Item No. Pay Item Pay Unit 302-01 Class II Base Course Cubic Yard 302-02 Class II Base Course ____ in Thick Square Yard