307.01 Subgrade Treatment
182 Before mixing is complete, uniformly moisten the mixture for the length of the section being treated to ensure workability and prevent excess wet and dry spots in the finished blend. Avoid using excess water during mixing and placing to prevent undue softening of the subgrade.
C.Spreading Spread the caliche base material uniformly over the length and wi dth of the section after the Resident Engineer tests and approves the blended windrow. Prevent segregation of the mixture. Ensure that the thickness of each layer of caliche base material does not exceed the compaction equipment’s capability to obtain th e specified density.
D.Compaction -Density Uniformly moisten each layer during compaction and continue rolling to produce a density of at least 100 percent of maximum density, determined in accordance with AASHTO T 99.
E.Tolerances Finish the caliche base in accordance with Subsection 301.04.A, "Tolerances. "
305.05 Method of Measuremen T
The Resident Engineer will measure the volume of the compacted in -place Caliche Base by multiplying the completed length of caliche b ase by the area of the typical section shown on the Plans.
305.06 Basis of Payment
The Department will pay for each pay item at the contract unit price per the specified pay unit as follows: Pay Item: Pay Unit: CALICHE BASE Cubic Yard [Cubic Meter]
307.01 Description
This work consists of providing, placing, and compacting one or more layers of a mixture of soil, chemical additives, and water to achieve a stable subgrade. Chemical additives used to stabilize or modify are defined as cementitious additives (portland cement, fly ash, or cement kiln dust) or lime additives.
A.Subgrade Stabilization Incorporate chemical additives into the subgrade to increase the strength of t he subgrade soils and to provide structural value for the pavement structure. SUBGRADE TREATMENT 307.04
B.Subgrade Modification Incorporate chemical additives into the subgrade to change the PI of the subgrade soils and improve its workability as a platform to support construction equipment. Determine soluble sulfate content of the soil in accordance with the Department's Materials Division test method OHD L -49 on projects where sulfate soils may be present, especially for projects in Field Divisions 4, 5, 6, and 7. Determine the applicability of subgrade treatment in accordance with OHD L-50 and OHD L-51. Do not perform subgrade treatment if sulfate content exceeds the threshold value specified in OHD L-49, OHD L-50, and OHD L-51.
307.02 Materials
Provide materials in accordance with the following subsections: Material: Subsection: Portland Cement 701.02 Water 701.04 Fly Ash 702.01 Cement Kiln Dust 702.03 Hydrated Lime 706.01 Quick Lime 706.02 Store all additives in a building or compartment that will protect them from dampness and allow easy access for inspection and identification of each shipment. Do not mix additives from different sources in storage. Do not mix lime from different sources in storage. Do not use additives that have been contaminated or exposed to moisture.
307.03 Equipment
Provide subgrade stabilization equipment in accordance with Subsection 301.03, “Equipment.”
307.04 Construction Methods
A.General Regulate the sequence of subgrade treatment, use the prescribed amount of additive, and maintain the work or rework. Complete a layer of treated material containing a uniform mixture of soil, additive, and water that has the following characteristics: No loose or segregated material, Uniform density and moisture content, Full depth compaction, and A smooth surface suitable for placing subsequent courses.
B.Weather Limitations Apply additives for subgrade stabilization when the air temperature is at least 40 F [4 C] and rising. Apply additives for subgrade modification when the air temperature is at least 33 F [1 C] and
307.04 Subgrade Treatme Nt
184 rising. Measure the air temperature at a location 4 ft [1.2 m] above the ground, in the shade, and away from artificial heat. Do not apply additives if the ground is frozen. Protect the quality of the additive and treated subgra de from the weather.
C.Preparation of Existing Roadbed Before beginning any subgrade treatment, shape and compact the roadbed to the dimensions and elevations indicated in the Plans or directed by the Resident Engineer. Roll the subgrade and correct soft areas revealed by this rolling, as approved by the Resident Engineer.
D.Scarifying and Loosening Scarify and loosen the subgrade material before applying the additive if directed by the Resident Engineer. Scarify and loosen a length of roadway on which the additive application and mixing can be completed in one day. Avoid loosening the subgrade material below the depth of specified additive treatment. The Resident Engineer may waive portions of the work if excessive rock is encountered. Excessive rock is defined as subgrade material consisting of at least 25 percent particles with a dimension greater than 2½ in [63 mm]. Perform exploratory scarifying directed by the Resident Engineer to make an excessive rock determination.
E.Application Base the ad ditive type and final application rates on classification tests of the subgrade soil. The Department will perform the classification tests. If approved by the Resident Engineer, the Contractor may have tests performed by a Department -approved laboratory at no additional cost to the Department. Apply the additive at a rate prescribed by the Department's Materials Division procedures for stabilization (OHD L-50) or modification (OHD L-51). If available, a copy of a soils report may be obtained from the De partment's Office Engineer Division before the Bid Opening. The soils report consists of soil classification data and is for estimating purposes only. Refer to the Department's Materials Division Website for the most current OHD procedures. To propose th e substitution of a cementitious additive not indicated in the Plans, submit a proposal to the Resident Engineer for approval. In the proposal, include the following: The test results performed by a Department -approved laboratory; The recommended applicat ion rates; and The cost comparison of the planned and proposed additives. Do not substitute additives before the Resident Engineer approves the requested substitution. Provide equipment to control the additive application rate. If the classification of subgrade soil changes, establish a new application rate in accordance with the Department’s Division procedures for soil stabilization (OHD L -50) or modification (OHD L -51) before applying the additive.
1.Application of Cementitious Additive Use dry meth ods of application for placing the cementitious additive on the subgrade. Use approved types of spreading equipment that can distribute the cementitious additive uniformly. SUBGRADE TREATMENT 307.04 Do not apply cementitious additive using the slurry method. Do not allow the addi tive to become wet before mixing, and do not place on a wet subgrade. Do not apply cementitious additives if wind blows the additive off the subgrade work area. Replace lost additive at no additional cost to the Department. Complete on the same day mixi ng, compacting, and finishing subgrade areas where additives are placed. Remove additive exposed to moisture and replace before completion of the first mixing operation, at no additional cost to the Department. Pretreat subgrades requiring soil modification with lime, at the rate prescribed in the Materials Division policy for soil modification in accordance with Subsection 307.04.E.2, “Application of Lime Additive,” before applying the cementitious additive.
2.Application of Lime Additive Do not apply lime if wind blows the lime additive off the subgrade work area. Use approved types of spreading equipment that can distribute the lime additive uniformly. Place the lime o n an area of subgrade where the first mixing operations can be completed on the same day. Do not expose the lime additive to open air for more than six hours.
a.Dry Method
1.Quick Lime For quick lime, use Department -approved equipment that uniformly distributes controlled amounts.
2.Hydrated Lime Use bagged hydrated lime for dry -method application as approved by the Resident Engineer only under unusual circumstances or when it would be impossible or impractical to use other methods. Meet all applica ble Federal, State, and local laws. Ensure that the bagged lime shows the manufacturer’s certified weight.
b.Slurry Method Do not use compressed air in any of the slurry mixing methods. Mix lime with water into a slurry using one of the following metho ds that will maintain the lime and water slurry in a uniform mixture until spread:
1.Central Plant Meet mixing requirements using integral paddles, recirculating pumps, or other devices. Equip the slurry distributor truck with a recirculating pump or agi tator that can keep the lime and water in a uniform mixture until spread.
2.Transit Mix Weigh or meter the lime from the storage bin into the tank transit mix truck using a Department -approved method. Equip the tank transit mix truck with a recirculating pump or agitator that can maintain a uniform mixing of lime and water while in transit.
307.04 Subgrade Treatment
186 Equip the distributor truck with a pump. Apply the slurry through spray bars under pressure to assure a uniform flow and distribution. Ensure that the slurry mixture meets the following: At least 1 ton [0.9 Metric ton] of lime to 500 gal [1,893 L] of water, and A maximum of 40 percent lime.
F.Mixing Spread the additive, and mix with the subgrade continuously. Unless otherwise approved by the Resident Engineer, compl ete the mixing operation during the same day that the additive is applied. Before field mixing determine the optimum moisture content for maximum density of the compacted soil-additive mixture in accordance with AASHTO T-99. To account for moisture loss during the mixing process, increase the moisture content by 2 percentage points to 5 percentage points above the optimum moisture content for the mixture. Use a pulver mixer equipped with a spray bar in the mixing chamber and capable of producing a soil-additive mixture with a moisture content within the specified range. Use a Department -approved mixing procedure that uses traveling mixing equipment that uniformly disperses the additive and water through the soil.
1.Mixing for Cementitious Additive Treat ment Reduce the size of the soil -additive mixture to meet the following gradation requirements: Table 307:1 Soil-Additive Mixture Gradation Sieve Size Percent Passing 1½ in [37.5 mm] 100 ¾ in [19.0 mm] ≥50 In a single mixing, achieve the gradation and moisture content requirements to the depths specified on the Plans. The Department will not pay for the second use of a pulver mixer if the Resident Engineer determines that the gradation or moisture content do not meet requirements. Modify the work pro cess to meet the above requirements in a single mixing if directed by the Resident Engineer. Provide cementitious additive and re -pulverization to the correct moisture content of any portion of the work area that the additive has hydrated before compaction at no additional cost to the Department, unless waived by the Resident Engineer.
2.Mixing for Lime Treatment
a.First Mixing Mix the soil, lime, and water to achieve a uniform mixture of material with a maximum diameter of 1½ in [37.5 mm]. Add water i n the first mixing process to ensure proper chemical reaction between the lime and soil. Allow the mixture to cure. When using hydrated lime, allow a curing time of 72 hr at temperatures above 40 F [4 C]. When using quick lime, allow a curing time of 48 hr at temperatures above 40 F [4 C]. SUBGRADE TREATMENT 307.04 The Resident Engineer may extend the cure time if the temperature falls below 40 F [4 C] during the curing period. The Department does not require cure time extensions for modification or lime pretreatment. Main tain the materials in a moist condition during the curing period. Seal the surface of the treated area by lightly rolling the surface to repel water and contain moisture. If directed by the Resident Engineer, rescarify portions of the treatment area and provide additional sprinkling to ensure proper moisture.
b.Quick Lime Mixing Minimize harmful exposure of workers to the heat of hydration. Use Department -approved means to turn under a significant portion of the quick lime within 2 hr after spreading a nd before adding water. To initiate hydration, add sufficient water within 6 hr after spreading. CAUTION: Uncovered quick lime in the presence of moisture may be hazardous to worker.
c.Final Mixing After the specified curing time, use Department -approve d methods to mix the material uniformly. Ensure the soil -lime mixture meets the following requirements: Table 307:2 Soil-Additive Mixture Gradation Sieve Size Percent Passing 1½ in [37.5 mm] 100 No. 4 [4.75 mm] 60 minimum
3.Mixing for Lime Pretreatment Provide the first lime mixing in accordance with Subsection 307.04.F(2)(a), “First Mixing.”
4.Mixing for Depths of At Least 8 in [200 mm] Compacted Thickness Do not exceed 8 in [200 mm] in depth for treated layers. For cut sections deeper than 8 in [200 mm], remove material above the bottom 8 in [200 mm] to treat the bottom layer. During normal fill construction, add and mix the specified amount of treatment additive to each 8 in [200 mm] layer. Com plete the fill construction as shown on the Plans. The Resident Engineer may approve the use of special equipment or methods to vary the mixing depths.
5.Mixing for Excessive Rock Areas In two separate stages, pulverize and mix excessive rock areas as di rected by the Resident Engineer. The Resident Engineer may waive the particle size requirement.
307.04 Subgrade Treatment
188 G. Compaction
1.General Compact the soil -additive mixture immediately after final mixing. Complete compaction on the same day as the mixing. Sprinkle and roll the soil -additive mixture. Scarify, reshape, sprinkle, and re -compact with rolling to immediately correct all irregularities, depressions, or weak spots.
2.Moisture -Density Requirements Compact before loss of mixing moisture occurs. Ensure compaction within 2 percentage points of optimum moisture content for the mixture. The Resident Engineer may authorize changes or adjustments in the moisture requirements. Conduct moisture -density tests on roadway samples to verify the target density for the soil - additive mixture before beginning compaction. Use the AASHTO T99 test method modified to provide one compacted specimen of the mixture. Uniformly compact the depth of the soil -additive mixture to at least 95 percent of target density. Determine field density in accordance with AASHTO T 310 or Subsection 202.04.A(5), “Compaction of Fill.”
3.Excessive Rock The Resident Engineer may adjust the requirements for soil -additive mixture uniformity, target densit y, and optimum moisture in excessive rock areas. Provide substantial compliance to the specification requirements in these areas, as approved by the Resident Engineer. The Resident Engineer may waive the density and moisture content requirements and appr ove compaction by visual observation.
H.Finishing and Curing Compact the final layer of the treated subgrade to the lines, grades, and typical sections shown on the Plans. Finish the completed section with a light roller to prevent hairline cracks. Spri nkle the treated subgrade to maintain the moisture content until placing a prime coat seal or succeeding layer. Do not place construction loads or operating equipment until the treated subgrade has cured and can withstand the loads without damaging the sub grade. If the subgrade deforms under the construction loads and cannot return back to its original condition, or if it deflects more than 1 in [25 mm], allow the subgrade additional curing time before operating equipment on the subgrade. The Department will not pay for the replacement and refinishing the treated subgrade if the material loses the required stability, density, or finish before the next course is placed. SUBGRADE TREATMENT 307.06
I.Tolerance Finish the treated subgrade in accordance with Subsection 301.04.A, “Tolerances.” After completing the final grade, use a color -sensitive indicator solution, such as phenolphthalein or thymol blue, to measure the thickness and uniformity of the compacted soil and chemical mixture in accor dance with Subsection 301.04.A(2), “Width and Thickness. ” Apply the indicator solution along the side of a small hole excavated to the required depth of chemical treatment and note the depth and uniformity of the c olor change.
307.05 Method of Measuremen T
The Resident Engineer will measure the area of completed in -place Cementitious Stabilized Subgrade, Cementitious Modified Subgrade, Lime Pretreatment, Lime Stabilized Subgrade, Lime Modified Subgrade, Modified Subg rade, and Stabilized Subgrade.
307.06 Basis of Payment
The Department will pay for each pay item at the contract unit price per the specified pay unit as follows: Pay Item: Pay Unit:
A.FLY ASH Ton [Metric Ton]
B.CEMENT KILN DUST Ton [Metric Ton]
C.PORTLAND CEMENT Ton [Metric Ton]
D.LIME Ton [Metric Ton]
E.CEMENTITIOUS STABILIZED SUBGRADE Square Yard [Square Meter]
F.CEMENTITIOUS MODIFIED SUBGRADE Square Yard [Square Meter]
G.LIME PRETREATMENT Square Yard [Square Meter]
H.LIME STABILIZED SUBGRADE Square Yard [Square Meter]
I.LIME MODIFIED SUBGRADE Square Yard [Square Meter]
J.MODIFIED SUBGRADE Square Yard [Square Meter]
K.STABILIZED SUBGRADE Square Yard [Square Meter] The Department will not pay for lime exposed to ope n air for more than six hours, or for lime lost due to excessive washing or blowing. If Selective Subgrade Topping is a separate pay item, the Department will consider the cost of cementitious or lime additives to be included in the contract unit price for the relevant subgrade modification or stabilization pay item. The Department will pay for quick lime based on a 90 percent available lime index (using the rapid sugar method in accordance with ASTM C-25) and will calculate payments as a percent of CaO by weight. The Department will pay for hydrated lime based on a 90 percent available lime index (using the rapid sugar method in accordance with ASTM C-25) and will calculate payments as percent Ca(OH) 2 by weight.
310.04 Subgrade
190 If the available lime index for quick lime or hydrated lime falls below 90 percent, the Department will reduce the payment by 1 percent of the lime contract unit price for each 1 percent from 90 percent to 80 percent. If the available lime index falls below 80 percent, the Department will not pay for the additional lime necessary to bring the available lime index to 90 percent. The Department will consider the cost of excavating layers deeper that 8 in to be included in the contract unit price for the relevant subgrade modification or stabilization pa y item. The Department will consider the cost of water and rolling to be included in the contract unit price for the relevant subgrade treatment pay item. The Department will pay for Prime Coat in accordance with Section 408, "Prime Coat." The Department will consider the cost of chemical additives, at the specified rate for the appropriate soil classification in accordance with OHD L-51, to be included in the contract unit price for Modified Subgrade . The Department will consi der the cost of chemical additives, at the rate specified for the appropriate soil classification in accordance with OHD L-50, to be included in the contract unit price for Stabilized Subgrade . If a separate pay item for Selective Subgrade Topping exists, the Department will consider the cost of cementitious and lime additives to be included in the contract unit price for Cementitious Stabilized Subgrade, Cementitious Modified Subgrade, Lime Stabilized Subgrade, or Lime Modified Subgrade. SECTION 310 SUBGRA DE
310.01 Description
This work consists of preparing the existing materials for the immediate construction of subbase, base, pavement, or surface.
310.02 Materials — Vacant
310.03 Equipment — Vacant
310.04 Construction Me Thods
A.Subgrade Method A for Traffic -Bound Surface Course Shape and crown the width of the existing roadbed with a blade grader to the grade shown on the Plans. Complete the cross section to at least a 2 percent crown or as directed by the Resident Engi neer.
Source: Oklahoma Standard Specifications for Highway Construction, 2019 Edition. Pages 196–203 of 935.