363shall be at least 98 percent of the mean density obtained in the approved control strip. In addition, each individual test value obtained within a test section shall be at least 95 percent of the mean density obtained in the approved control strip.
304.06 Measurement and Payment
This item is considered incidental to the cost of furnishing, placing, and compacting the specified course and will not be measured for payment. The cost of constructing density control strips shall be included in the cost of the material for which the control strip is required. SECTION 305—SUBGRADE AND SHOULDERS
305.01 Description
This work shall consist of constructing the subgrade and shoulders to the cross section and grade shown on the plans and within the specified tolerances indicated on the plans and in these specifications.
305.02 Materials
Materials may consist of material in place, treated material in place, or imported material. Imported material may be borrow material, select material, or other material as shown on the plans or specified in the Contract. Materials other than regular excavation or borrow material that are shown on the plans or specified in the Contract shall conform to the applicable requirements of these Specifications. Geotextile materials used for subgrade stabilization shall conform to Section 245.03(d).
305.03 Procedures
a.Shaping and Compacting Subgrade:
1.Subgrade consisting of material in place: The subgrade area shall be scarified to a depth of 6 inches for a distance of 2 feet beyond the proposed edges of the pavement on each side. If sandy or other soil is encountered that will not compact readily, clay or other suitable material shall be added or water applied in such quantity and within the allowable moisture content specified herein as will permit compaction of the subgrade. Subgrade material shall be com - pacted at optimum moisture, within ±20 percent of optimum. The density of the subgrade when compared to the theoretical maximum density as determined in accordance with VTM-1 shall conform to the following: % Retained on No. 4 Sieve Min. % Density 0-50 100 51-60 95 61-70 90 Percentages of material shall be reported to the nearest whole number.305.03 364The Contractor shall then shape and check the subgrade to ensure a typical cross section and uniform grade prior to placement of any subsequent courses. If the subgrade becomes eroded or distorted prior to placement of material for subsequent courses, the Contractor shall scarify, reshape, and recompact it in accordance with the original requirements. At the time of placing material for subsequent courses, the Contractor shall compact the sub - grade to the required density, free from mud and frost, and to a condition that will permit compaction of subsequent courses without distortion. The Contractor shall remove material from the unstable area and contaminated aggregate if the approved subgrade becomes unstable after placement of the subbase or base course and becomes mixed with the aggregate therein. The area shall then be backfilled and compacted, and the subsequent course thereon reconstructed.
2.Subgrade consisting of treated materials in place: Subgrade shall be treated in accordance with the applicable provisions of Section 306.03 and Section 307.05 except that the tolerance for depth will be waived when lime or cement is being used to bridge or correct extremely weak areas. The Contractor will not be required to perform additional mixing and compacting if lime can be satisfactorily manipulated during initial mixing, and the Contractor has satisfactorily bridged the weak area. Additional layers of fill may be placed without delay. Field density determinations will be performed in accordance with AASHTO T310 and VTM- 10, modified to include material sizes used in the laboratory determination of density; with a portable nuclear field density testing device; or by other approved methods. When a nuclear device is used, the nuclear density determination for treated in-place subgrade material will be related to the density of the same material tested in accordance with VTM-1 or VTM-12 and a control strip will not be required.
3.Subgrade consisting of imported material: The area to receive the material shall be graded to a true crown and cross section. Material shall be placed and compacted in accordance with the applicable specifications governing the type of material. When select material is used, material shall be placed and compacted in accordance with Section 308.02 except that the provision for mixing will not be required. The Contractor shall compact the top 6 inches of the finished subgrade in accordance with the provisions of 1.herein. The provisions of 1. herein that are not specifically amended shall apply. Imported material shall be placed in approximately equal layers not more than 8 inches for commercial materi - al and 6 inches for local material, compacted measure. The Engineer will test material after compaction for thickness and density. If material fails to conform to thickness requirements, the Contractor shall correct the material by scarifying, adding material if necessary, mixing, reshaping and recompacting, or removing and replacing. If the material fails to conform to density requirements, the Engineer will require additional rolling until the required density is obtained provided the material is compacted at optimum moisture, within ±20 percent of optimum. If the moisture content is outside the allowable tolerance, the Engineer will require the layer to be scarified, brought to optimum moisture within the allowable tolerance, and recompacted to the specified density.305.03 365An aggregate spreader will not be required in the placement of select material and other imported materials used as subgrade and shoulder courses.
b.Treatment of Unsuitable Subgrade: When solid rock occurs in cuts or the material is not suitable for subgrade or finishing purposes, the roadbed shall be excavated below the grade shown on the plans in accordance with the Standard Drawings. When solid rock or other unsuitable material has been removed, excavated areas shall be backfilled in accordance with the Standard drawings.
c.Finishing Subgrade: The Contractor shall provide effective drainage for the subgrade and maintain it in a satisfactory condition until the next course is placed. When practicable, the subgrade shall be prepared at least 500 feet ahead of placement of any sub - base, base, or surface course. Material for subsequent courses shall not be placed until the subgrade has been checked and approved. The finished subgrade elevation shall be within ±0.04 foot of the plan elevation unless otherwise specified. When imported material is used, acceptance of the course will be based on Section 308.04.
d.Geotextile (Subgrade Stabilization): When geotextile for subgrade stabilization is required, it shall be placed as shown on the plans. Geotextile shall be spliced by an overlap of at least 2 feet or by sewing double-stitched seams with stitching spaced 1/4 inch to 1/2 inch apart or as shown on the plans.
e.Shoulders: Aggregate shoulder material shall be placed in accordance with the applicable specifications governing the type of material or construction being used and shall be compacted at optimum moisture, within ±2 percentage points of optimum. Except when aggregate material No. 18 is used, the density of the aggregate shoulder material, when compared to the theoretical maximum density as determined in accordance with VTM-1 or VTM-12, shall conform to the following: % Retained on No. 4 Sieve Min. % Density 0-50 100 51-60 95 61-70 90 Percentages of material will be reported to the nearest whole number. When aggregate material No. 18 is used, the density, when compared to the theoretical maximum density, shall be not less than 90 percent or more than 95 percent. Aggregate in the guardrail section of fills, 1 foot from the roadway side of the guardrail face to the outside of the shoulder, shall be compacted until a density of at least 90 percent of the theoretical maximum density has been obtained. The asphalt mixture in this area shall be sealed immediately after the hot mixture is spread. Rolling of the asphalt mixture shall continue until roller marks are eliminated and a density of at least 85 percent of the theoretical maximum density has been obtained. Stabilized and paved shoulders shall be constructed in accordance with the applicable specifications for pavement stabilization. If the aggregate shoulder material becomes overconsolidated prior to 305.03 366final finishing, it shall be scarified for the approximate depth, reshaped, and recompacted to conform to the specified grade and cross section. Shoulders shall be constructed simultaneously with nonrigid types of base or surface courses other than asphalt concrete or in advance of the base or surface course so as to prevent spreading of base or surface materials. The area of shoulders 12 inches adjacent to the pavement shall be rolled simul - taneously with the course being deposited. Where base or surface courses are being constructed under traffic and are more than 1 inch in depth, shoulder material adjacent thereto shall be placed within 72 hours after placement of the base or surface course.
305.04 Measurement and Payment
When material in place is used for the subgrade and shoulders, no measurement will be made by the Engineer. Treated material in place will be measured in accordance with the method of measurement for the specified stabilizing material. When imported material is specified, it will be measured as follows:
a.Select material, Type I, will be measured in tons.
b.Select material, Types II and III, will be measured in cubic yards in its original position.
c.Borrow will be computed in its original position by cross-sectioning the area excavated. If cross- sectioning the area excavated is not practical, the quantity will be determined from compacted measurements in the road and then converted to pit volume. When cubic yard measurement is specified and the plans do not show the thickness of material required, the material will be measured in the original position by the cross-section method. Where it is impractical to cross-section the area, measurement will be made in trucks in accordance with Section 109.01. When the ton unit is specified, the quantity will be determined in accordance with Section 109.01. The Engineer will deduct moisture in excess of optimum, + 2 percentage points from the net weight of both truck and rail shipments. Allowance will not be made for unauthorized depths beyond those shown on the plans and the allowable tolerances. When tonnage measurement is used, the Engineer will deduct for material exceeding the allowable tolerance based on 110 pounds per square yard per inch of depth. When material in place is used for subgrade and shoulders, no separate payment will be made. The cost thereof shall be included in the price for other applicable pay items. When imported materials are used, the subgrade and shoulders will be paid for at the contract unit price per cubic yard or per ton as specified. Treated material in place will be paid for in accordance with the applicable specification. Stabilized or paved shoulders shown as a pay item will be measured and paid for in accordance with Section 306.04, Section 307.06, Section 312.05, or Section 315.08, as applicable.305.03 367These prices shall include furnishing, hauling, placing, manipulating, and compacting material; clearing and grubbing local pits; material royalties; and access roads. Geotextile for subgrade stabilization will be measured in square yards, complete-in-place. Overlaps and seams will not be measured for separate payment. The accepted quantity of geotextile will be paid for at the contract unit price per square yard. This price shall include furnishing, placing, lapping, or seaming material. Payment will be made under: ——————————————————————————————— Pay Item Pay Unit——————————————————————————————— Borrow excavation Cubic yard Select material (Type and min. CBR) Cubic yard or ton Aggregate material (No.) Cubic yard or ton Aggregate base material (Type and no.) Cubic yard or ton Geotextile (Subgrade stabilization) Square yard——————————————————————————————— SECTION 306—LIME STABILIZATION
306.01 Description
This work shall consist of stabilizing roadbed material by constructing one or more courses of the pave - ment structure using a mixture of soil or approved aggregates, lime or lime and fly ash, and water.
306.02 Materials
a.Lime shall conform to Section 240.
b.Fly ash shall conform to Section 241. Bulk fly ash may be transported dry in bulk trucks and stored in tanks or may be transported in the dampened condition, with a maximum of 15 percent moisture, and stockpiled at the job site. The Contractor shall not use excessively wet or contaminated surface material in mixing operations. The Contractor shall cover stockpiled material with a non-absorptive cover material or periodically moisten the fly ash to prevent moisture loss and it from becoming airborne.
c.Water shall conform to Section 216.
d.Aggregates shall conform to Section 205, Section 207, and Section 208 as applicable, or other requirements as described in the Contract.
306.03 Procedures
The Engineer will not allow lime stabilization when aggregates or the surface on which the course is to be placed is frozen. Manipulation shall not be started until the surface is free from mud or frost and the ambient air temperature is at least 40 degrees F .306.03
Source: Virginia Road and Bridge Specifications, 2020 Edition. Pages 391–394 of 1,065.