310CRUSHED AGGREGATE BASE COURSE

310.1DESCRIPTION—This work is construction of a stone or slag base course. When placed on subgrade, it

includes the preparation of subgrade, as specified in Section 210.

310.2MATERIAL—

follows: Stone having unsatisfactory cementing qualities may be used, provided limestone fines in an amount of 20% are blended with the material. Acceptable granulated blast furnace slag, meeting the gradation requirements for No. 10 aggregate may be used. Granulated blast furnace slag, formed when molten iron slag is rapidly quenched in water, is acceptable providing it does not have a density greater than 90 pounds per cubic foot (dry rodded density, AASHTO T 19). Slag material reasonably uniform and free from harmful amounts of clay, silt, vegetation, or other objectionable substances, is acceptable with a maximum size of 2 inches and not more than 20% passing the No. 100 sieve.

310.3CONSTRUCTION—

base material without segregation.

equipment as required for Method 2.

of base course, before placing base course; or build up and roll shoulders simultaneously with compaction of each layer.

template cut to the required cross section of the finished base course. Equip the template with metal or other vertical extensions attached to each end, so the bottom of the template will be at the elevation of the top of the base course. Furnish at least three templates. Test the cross section for surface irregularities at intervals of not more than 25 feet. Use a 12-foot straightedge to test for longitudinal irregularities in the surface of the base course. Hold the straightedge parallel to the road centerline in contact with the surface. Move the straightedge from one side of the base course to the other. Advance along the base course in 5-foot increments. Refer to Section 210.3(d) for GPS or Laser Controlled Equipment.

replacement. Remove pavement in these areas to neat lines, as specified in Section 203.

spread and compact by another acceptable method. If base course material is placed on existing pavement as an overlay or build-up, construct in compacted layers. If subgrade or subbase materials become mixed with the base course, remove the mixture; reshape and recompact the subgrade and/or subbase; reconstruct the unsatisfactory base course area. Use calcium chloride only when and as directed.

subbase, or existing pavement as a bed and filler; spread to a depth of 2 inches on subgrade, or 1 inch on subbase or existing pavement. Do not place this initial layer of fine material on wet, frozen, or unsuitable subgrade or subbase.

If the base course is more than 8 inches in compacted depth, construct in two or more layers of approximately equal depth, with no layer less than 4 inches nor more than 8 inches in depth.

unless otherwise specified. In areas inaccessible to spreading equipment, spread material directly from trucks, if allowed. Remove segregated material and replace with well -graded material. Do not spread the material more than the distance completed in an average day's work ahead of choking and compacting, as specified in Section 310.3(c)3 and (c)4, respectively. Test each layer of material for surface irregularities, as specified in Section 310.3(b)2, and correct irregularities before rolling.

to the center. On superelevated curves, begin on the low side and progress to the high side. Install string lines with ample supports, offset along each side to control the elevation and depth of the base course. Maintain string lines until the base course is completed and the deficiencies have been corrected. Roll parallel with the roadway centerline, uniformly lap each preceding track, cover the entire surface with the rear wheels, and continue until the material does not creep or wave ahead of the roller wheels. Place red flags at the initial limits of compa cted coarse material completed. The flags will be moved ahead as ad ditional material is compacted. Do not apply filler to the coarse material outside of the flag - marked sections.

uniformly over the surface with spreading equipment, to assure filling voids. In areas inaccessible to equipment, spreading with a square -edged shovel may be used; spread in a sweeping motion alternately in opposite directions, until the voids are filled. Do not end-dump the material directly on the surface of the coarse material. Immediately following the spreading, sweep and roll the material until remaining voids in the coarse material are filled and the base course i s thoroughly compacted and set. Use brooms attached to the roller and hand brooms. Loosen and scatter excess fines formed in piles or cakes upon the surface. Spread and roll the material in sections of not less than 150 feet nor more than 1,000 feet in length, unless otherwise directed. Compact and bond each section, as specified in Section 310.3(c)4, before beginning another.

Cover the entire surface with the rear wheels, applying additional fines where necessary to fill voids, and continue rolling until the base course is thoroughly compacted and set. After completion of spreading and rolling of fines, sprinkle with water and roll the surface of single - layer construction or roll the surface of each layer of multi-layer construction. Perform diagonal and cross- rolling, as required or directed. Continue the sprinkling and rolling, applying additional fines until voids are filled and a slight wave of grout forms in front of the roller wheels. Use roller-attached brooms and hand brooms to distribute the grout uniformly, filling the voids. Allow the rolled section to dry before proc eeding with the surface course. Sprinkle and reroll the surface on succeeding days, as required, to thoroughly bond and to provide a satisfactory base course. The Inspector-in-Charge will determine the quantity of fines and water required to produce a smooth, hard monolithic surface.

Sprinkle water, using acceptable methods.

If the base course is more than 10 inches in compacted depth, construct in two or more layers of approximately equal depth, with no layer less than 5 inches nor more than 10 inches in depth.

compact, using vibratory equipment. Roll the layer, as specified in Section 310.3(c)2.

rolling, spread fine material uniformly over the surface in an amount equal to about one-half of that required to fill the voids in the coarse material. Operate the vibrator over the surface so the fines settle into the voids. Spread and vibrate the remaining fines in one or more applications to satisfactorily fill the voids; however, do not cause flotation of the coarse aggregate. Use manual methods to fill areas not completely filled by vibration.

with water and roll. Continue the operation, as specified in Section 310.3(c)4.

310.3(b)2. Correct all surface irregularities exceeding 1/2 -inch by loosening the surface and removing or addi ng material as required. Compact the corrected area and surrounding surface by rolling.

directed, for each 3,000 square yards or less. The Representative will measure the depth of the base course. The initial bed and filler layer of fine material is considered part of the base course for determining the final compacted depth. Remove and replace any area in which the depth is deficient by 1/2 -inch or more. Additional test holes may be required, if directed, to determine the limits of replacement areas. After the depth has been measured, backfill test holes with acceptable material and compact.

as specified in Section 901.3(b). Maintain and protect base course opened to traffic by authority of the Representative, as specified in Sections

107.15and 901

Allow only necessary local traffic and essential construction equipment on the base course, unless otherwise directed. Repair or replace marred, distorted, or otherwise damaged pavement.

310.4MEASUREMENT AND PAYMENT—