SECTION 321 - IN-GRADE PREPARATION
321.01 Description. The term "in-grade preparation" is defined as the work required to
prepare, blade, shape, scarify, disk, mi x, compact, etc. the existing material to specification requirements prior to placement of a subsequent course of material. Figure 1, Section 101, graphically defines the limits of the roadway, the design soil and the components of the pavement structure. In-grade preparation shall be in reasonable close conformity with the lines, grades, and typical section(s) shown on the plans. All work will be performed in the sequence and timing specified. No direct compensation will be allowed for in -grade preparation, except as specifically provided herein.
321.01.1 Applicability. In-grade preparation will be required on all projects that require
replacement of any component of a pavement structure or chemical treatment of the design soil. In-grade preparation will not be required on pavements or chemically treated courses that are to remain in place undisturbed. Unless otherwise specified, the in-grade preparation course shall be the top six inches of the design soil.
321.02 Blank.
321.03 Construction Requirements.
321.03.1 General. Prior to beginning in-grade preparation, the roadway will be cleaned
of all vegetation or debris, bl aded, shaped an d filled as necessary to obtain the required line, grades and typical section as shown on the plans or as specified. The Contractor will perform unclassified excavation where re quired for grade changes, removal of temporary ramps at bridge ends, shape foreslopes and cut ditches to the required line, grade and typical section, and other work required to alter work performed on previous contracts. All material obtained in preparation prior to in-g rade preparation work will be disposed of or utilized by the Contractor.
321.03.2 First In-Grade Course.
321.03.2 1--Design Soil. When the first in-grade preparation course is the top portion of
the design soil, which was constructed under a previous contract, the top six inches, unless a greater depth is specified, shall be broken up, either by scarifying or blading to the specified depth and then thoroughly mixed by a disk-harrow. If the embankment design soil was constructed under this contract in accordance with the requirements of Section 203, then only the cut section will require mixing as stated herein. The disk shall be of sufficient weight and size to cut a mi nimum depth of eight inches, or ten inches when eight inches design soil mixing is required, in loose material. After mixing with a disk-harrow, the roadway will be shaped and compacted to the proper section and density.
321.03.2 2--Component of Pavement Structure . When the first in-grade preparation
course is a component of the pavement structure, other than design soil, the course shall be prepared by blading, shaping to the speci fied section, and compacting to the specified density for the particular layer being prepared.
321.03.3 Unsuitable Materials . All materials which cannot be stabilized and
compacted to the required density, shall be removed and disposed of as directed. The material removed will be replaced by acceptable materials. Unless the unsuitable material was placed under this contract, the removal, dis posal, and replacement of the material will be measured and paid for under the appropriate items of the contract. Materials that meet contract requirements, except for moisture content, will not be classified as unsuitable materials.
321.03.4 Stability. When density and stability cannot be obtained due to the instability
of the underlying material, the Contractor will take the necessary action to stabilize and compact the underlying material. Unless th e unstable material was placed under this contract, the work required to stabilize and compact the material will be paid for under the appropriate items of the contract. When the Contractor has initiated appropriate action to stabilize and compact the underlying material and density cannot be obtained, then the material will be classified as unsuitable and proceed in accordance with Subsection 321.03.3.
321.03.5 Haul, Protection and Repair . All materials hauled through or over any part
of the project shall be hauled in the sequence and manner to cause the least damage to the previously placed course. The Contractor's operations shall provide the maximum protection to each course in place from deformation or c ontamination from underlying material. The first course of material to be placed on a chemically treated design soil shall be placed by hauling to the point nearest the source of the material, thus hauling over the material being placed. Subsequent hauling shall be over the maximum practical thickness of material in order to provide the greatest protection to the underlying material. The Contractor shall satisfactorily maintain the material over which he is hauling, and the materials being hauled shall be spread as hauling progresses to prevent hauling equipment from repetitive passes alongside lines of dumped and unspread material. The Contractor shall repair, at no additional cost to the State, all damage to prepared in- grade material whether the material was placed under this contract or under previous contract.
321.03.6 Density. The required density for in-grade preparation of courses that do not
require a chemical treatment or modification shall be the required density for the particular course. The required density for courses that require chemical treatment or modification shall be 93.0 percent prior to the addition of the chemical, stabilizer or modification.
321.03.7 Tolerances.
321.03.7 1--General. It shall be understood that although certain tolerances in grade,
cross section, and density are allowable under the specifications, it shall be the Contractor's responsibility to prepare the surface of all in-gra de courses to the degree of true grade and cross section and to the density and stability necessary to ensure the ability to construct subsequent courses to the specified requirements for surface, thickness, and compaction. It is essential in pavement structure construction that the degree of accuracy must be increased for each succeeding course in order that the final surface requirements can be met and the thickness of each course will be within design tolerances. It shall be the Contractor's responsibility to construc t each course to the degree of accuracy, maximum allowable tolerances notwithstandi ng, necessary to ensure meeting final requirements.
321.03.7 2--Vertical Tolerances. No vertical tolerances will be allowed that will pond
water. Otherwise, allowable tolerances will be as follows:
321.03.7 2.1-For Design Soil.
Tolerances from Design Grade:
a.Where the top portion of the design soil is to be lime treated or lime-fly ash treated and the next course is stone or is to be chemically treated - - Before Treatment -1" (1) - Treatment In Place ±1" (2)
b.Where the top portion of the design soil is to be cement treated and the next course is stone or is to be chemically treated - - Before Treatment -1" - Treatment In Place -1"
c.Where the design soil is not to be treated and the next course is stone or is to be treated or untreated - - Preparation In Place -1"
d.Where the design soil is not to be treated and a superimposed course is not required under this contract - - In Place ±1" Notes: (1) From the design grade established before spreading lime to allow for bulking.
2.From the design grade established for bulked material.
321.03.7 2.2--For Bases.
The surface tolerances from design grade be fore placing base material shall be the tolerances from design grade in place as set out herein for design soils. Grade stakes or other reference points shall be set at 25-foot intervals; when tested longitudinally, the maximum deviation when measured at the midpoint (12½ feet) shall be ±1/2 inches.
a.Where a base course is not to be treated and the next course is to be bituminous pavement - - In Place ±1/2"
b.Where a base course is stone or is to be cement treated and the next course is a drainage layer - - In Place ±1/2"
c.Where a base course is to be lim e-fly ash treated and the next course is a drainage layer - - In Place ±1/2" (3)
d.Where a base course is stone or is to be cement treated and the next course is to be bituminous pavement - - In Place ±1/2"
e.Where a base course is to be lim e-fly ash treated and the next course is to be bituminous pavement - - In Place ±1/2" (3) Note: (3) From the design grade established for bulked material. Where stone is specified, it shall meet the requirements of Section 304.
321.03.7 2.3-For Drainage Layers.
Tolerances from Design Grade: Where a drainage layer is requ ired - - In Place +1/8” to -3/8"
321.03.7 2.4--For Any Course.
Tolerances from Design Grade:
a.Where a course is to be stone or is to be treated or untreated and the next course is a drainage layer or bituminous pavement - - In Place ±1/2"
b.Where a course is stone or is to be treated, followed by a drainage layer and concrete pavement - - Under the Form Line or Track Line ±1/8" (4) - Elsewhere -1" (5) Notes: (4) The Contractor may construct the course at the form line to a tentative grade having a tolerance of not more than minus 1/2 inch, in which case the Contractor shall, at no additional cost to the State, bring the surface of the base at the form line to the speci fied grade and density with materials and methods approved by the Engineer and consistent with the requirements for foundation formation for forms or tracks required under the contract.
5.Provided the Contractor places at no additional cost to the State, at the time of placing concrete base course or pavement, the additional concrete necessary to compensate for the deficiency from a true design base grade.
321.03.7 2.5--For Mechanical Stabilization and In-Grade Modification . Where
material is to be mechanica lly stabilized or modified with stabilizer aggregate or other materials on the roadbed, the tolerance from design grade, both before spreading the aggregate and after mechanical stabilization, shall be those as respectively set out hereinbefore with an appropriate allowance having been made in the grade prior to spreading the aggregate to compensate for anticipated bulking.
321.03.7 2.6--Thickness. Unless otherwise specified and except for chemical treatment,
mechanical stabilization, in-grade modification, and in-grade preparation of the top portion of the design soil, no thickness determination as such will be required for bases. The preceding tolerances from design grade shall determine the tolerance limits for thickness. The thickness tolerance for in-grade preparation of the top portion of design soil shall be plus or minus one inch. For chemical treat ment, mechanical stabili zation, or in-grade modification, thickness tolerances shall be those set out in the sections applicable to the required courses.
321.03.7 3--Horizontal Tolerances. Allowable horizontal tolerances for in-grade
preparation shall be those set out in the respective sections for the required courses. Where no horizontal tolerance is specified, th e tolerance for a course shall be that which will not result in an unsightly appearance or detract from the esthetic value of the finished crown line and slope. Each course of base and shoulder materials, and combined courses of shoulder materials and the top portion of the design soil shall be shaped in such a manner that after compaction the finished course and combined courses shall closely conform to the widths, lines grades, and cross sections shown on the plans or established.
321.04 Method of Measurement. Unless shown as a separate pay item in the proposal,
in-grade preparation will not be measured for direct payment, but shall be considered a necessary part of the construction involved, and the cost thereof shall be included in the appropriate contract unit prices. When shown as a separate pay item, in-grade preparation of the depth specified will be measured by the mile for each separate roadway of the main facility without respect to width or number of lanes or courses involved. No separate measurement for payment will be made for frontage roads, interchanges, intersections, entrances, or other features of the work, nor for intersecting roads unless such roads are set out under the contract as separate projects. It shall be understood that the cost of in-grade preparation for such subsidiary facilities is included in the contract unit price per mile for the main facility. In the case of in-grade preparation of material in place under previous contract, if it is necessary to excavate, pickup, load, and haul any of the in-grade material for use at other locations or for disposal as directed in order to prepare the section in accordance with the design grade, typical sections and conditions specified, such work shall be performed and will be measured and paid for under the applicable provisions and requirements as follows:
a.When designated in the contract, under the provisions and requirements designated.
b.When material loaded and hauled is used in lieu of material required under another item, measurement and payment will be made under the item of use.
c.Measurement and payment for base or pavement material required in the work performed will be made in accordance with the requirements and provisions for use of such material.
d.When an item of excavation is not included in the contract, excavation required by the Engineer to be picked up, loaded, and hauled to other locations will be paid for as Extra Work or at unit prices established by Supplemental Agreement.
e.Necessary haul of material not specified to be furnished by the Contractor, or not designated as absorbed haul (AH), shall be performed and will be paid for as provided under Section 205, or, in the event the contract does not provide a unit bid price for haul, as Extra Work.
321.05 Basis of Payment. Except as provided above, no payment will be made for in-
grade preparation. It shall be fully understood that compensation: for all specified scarifying, disk-harrowing, mixing, or other processing; for furnishing and applying all water; for all aerating necessary to dry wet materials; for all shaping and compacting; for all other work of whatever nature necessary for preparation as set forth under this section; and for furnishing all labor, tools, equipment and incidentals necessary to complete the work shall be included in the unit prices for the materials used and the work performed under contract items. When shown as a separate pay item in the contract, in-grade preparation will be paid for at the contract unit price per mile, which price shall be full compensation for satisfactorily completing the work. Payment will be made under: 321-A: ___" In-Grade Preparation - per mile
Division 400 — Division 400
Division 400 — Bituminous Pavements
Referenced in this section
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Source: Standard Specifications for Road and Bridge Construction, 2017 Edition. Pages 245–251 of 1,113. View official source ↗