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<br />4275
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<br />mineral aggregate; haulil'lg, placing, blading, mixing,
<br />and compacting the subbase course; and an
<br />. incidenta' work connected therewith.
<br />
<br />272. BASE COURSE
<br />
<br />a. Materials.- The mineral aggregate for base course
<br />shall be furnished by the contractor, shall consist of
<br />Quarry waste, broken stone, crushed gravel, or a
<br />combination thereof and shall be uniform in quality
<br />and grading. The 'aggregate shall be free from adobe,
<br />vegetable matter, loam, and other deleterious
<br />substances and shall be of such quality that it will
<br />compact thoroughly when watered and rolled to
<br />form a firm well-bonded base. When tests indicate
<br />the material is deficient in binder, additional soil
<br />binder shall be added to the material on the road
<br />but only in such amounts as will insure the total
<br />material conforming to the following requirements.
<br />Soil binder shall be pulverized before miXing with
<br />gravel or stone.
<br />
<br />11) Grading.-l"he aggregate when tested by
<br />means of standard screens (Designation 4)' shall
<br />conform to the following limits of gradation:
<br />
<br />100 percent passing a screen with
<br />3/4.inch-square openings;
<br />30 to 60 percent passing a No.4-mesh screen;
<br />25 to 50 percent passing a No. a.mesh screen;
<br />5 to 12 percent passing a No. 200.mesh
<br />screen; and
<br />Liquid limit not greater than 30 and the
<br />plasticity index shall not exceed six when
<br />tested in accordance with AASHO T89 and
<br />T90.
<br />
<br />(2) Quality.-When subjected to the Los Angeles
<br />abrasion test (Designation 21), the aggregate shall
<br />have a toss, using Grading A, not to exceed 50
<br />percent, by weight, at 500 revolutions. The
<br />designation in parentheses refer to methods of
<br />test described in the Seventh Edition of 'the
<br />Bureau of Reclamation Concrete Manual. The
<br />Government will test the aggregate, and the
<br />contractor shall provide such facilities as may be
<br />necessary for procuring representative test
<br />samples (Designation 1i.
<br />
<br />b. Placing.- The subbase course shall conform to
<br />line and grade before placing base course. The base
<br />course when thoroughly compacted shall conform
<br />to the grades and dimensions shown on the drawings
<br />or otherwise established, The base course shall be
<br />constructed in one course. Depositing and spreading
<br />the material shalt commence at the point farthest
<br />from the point of loading and shall progress
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<br />;Jl:r.'
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<br />C'
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<br />SPECIFICAtiONS NO. DC'6945~";"
<br />. .. . ~ .
<br />(SUPPLEMENTAL NOTICE N~J~...,
<br />
<br />Par. 27~,;:~
<br />. '." .--.::.ti,~
<br />continuously without brea"ks, exc~pt' as dt"tler1!'t~ .
<br />. ~~ll.' I
<br />directed. The material shall be spread from ,~.
<br />hauling veh~cle ~y h~nd: from spre~din~ bo'~~;s1V,
<br />from self.-spreadlng" vehicles. Dump~ng.. In ~~I?:~i'. ~.
<br />the 'subbase. course will not be permitted.' .'"
<br />material shall be deposited and spread in a laye' ~f:
<br />uniform thickness and of such'. depth '. that att~,
<br />being compacted the course will be 'of the reqli~d
<br />thickness, After the material has been spread, '.;.tt
<br />shall be mixed thoroughly, by a heavy blade graller
<br />having a wheel base not less than 15 feet long, ui{iil.
<br />the materia\ shows a uniform mixture of a\\ size~.of
<br />"
<br />particles. Wetting may be necessary to obtain pro~e~r
<br />mixing.
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<br />c. Compacting.-Rolliri9 of the material sh.~1I
<br />commence immediately after it has been mixed"~~s
<br />described above. Rollers shall weigh from 7 torn'
<br />,.
<br />tons and shall be of the steel smooth-wheel tYpe:
<br />Rolling shall commence at the outer edges of i~.e
<br />course and shall progress toward the center. Under
<br />no circumstances shall the center of the courselhe
<br />rolled first. Sufficient water to obtain compacti.on .
<br />t shall be applied during the rolling operations. Each
<br />course shall be compacted to a dry density,: in
<br />accordance with either of the following control t~sts
<br />,
<br />whichever shows the higher dry unit weight' . ,
<br />
<br />(1) N inety.five percent of the laborato~y
<br />standard maximum soil density (dry) ;.a..'
<br />r
<br />determined by the Bureau of Reclamati'on
<br />';'..j:
<br />Proctor Compaction Test, or ';.1.
<br />
<br />(2) The dry density of the material at 70 perJnt
<br />'tJ..
<br />relative density as determined by the rela'lve
<br />density test. t
<br />
<br />d. Measurement,- The quantity of male;;al for base
<br />Course for which payment will"-:!'J\;' :"'~~e will 'be
<br />~ " " ". ,I ,
<br />determined as provided in }~,~!~gyap,h 268. T-he
<br />...ight of base-course materia' Ipr which paym~nt
<br />will be made will be the total weight of the minJ~al
<br />aggregate and binder. ..
<br />
<br />e. Payment.-Payment for base course will be rni;l:de
<br />at the unit price per ton bid therefor in '.tQe
<br />schedule, which unit price shall include the cos.tbl:
<br />preparing the subbase; furnishing all materi'als,
<br />including binder and water incorporated with .the
<br />mineral aggregate; hauling, placing, blading, mi"t~g,
<br />and compacting the base course; and all incidental
<br />work connected therewith.
<br />
<br />273. FINISHING ROADWAY
<br />
<br />a. Generai.-After the earthwork has been
<br />completed and before the bituminous surfacing and.
<br />
<br />259
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