SECTION 306–FULL DEPTH RECLAMATION

306.01 DESCRIPTION

This Section describes Full Depth Reclamation (FDR) with cement consisting of pulverizing existing flexible pavement to the specified depth and in place mixing of the asphalt pavement, base course and/or subbase with Portland cement and water to produce a dense, hard, cement-treated base course.

306.02 MATERIALS

306.02.01 Materials

Provide Materials conforming as specified:

Water 919.08

Cement 903.01

Tack Coat:

Emulsified Asphalt, Grade SS1, SS1h, CSS1, or CSS1h …………………………………..…………………..902.01.03

Corrective Aggregate:

Coarse Aggregate 901.03

Reclaimed Asphalt Pavement (RAP) 901.05.04

A. Preconstruction Sampling and Mix Design. Submit mix designs for approval to the ME at least 30 days prior to the start of FDR operations. Ensure that the mix designs conform to the procedures in PCA E052.07S Soil-Cement Laboratory Handbook and PCA EB234.02 Guide to Full-Depth Reclamation (FDR) with Cement except that Freeze-Thaw, Wet-Dry and Tube Suction Testing are not required. Perform the mix design with representative samples from the project site by obtaining one sample for every 1500 lane-feet and additional samples when material composition or thicknesses change. Perform a mix design for each change in material by an AASHTO approved laboratory experienced in full depth reclamation mixture design. When performing the mix design, crush and mix the HMA with the underlying base course and/or subbase at the percentages to be encountered in the field. Mix the blended material, which may also contain corrective aggregate, with cement at various rates that ensure a mixture with a 7-day compressive strength of 400 psi +/- 100 psi. Determine compaction density using ASTM D558, Standard Test Method for Moisture-Density Relations of Soil Cement. Determine compressive strength using ASTM D1633, Standard Test Method for Compressive Strength of Molded Soil-Cement Cylinders. Calculate the initial cement spread rate from the in-place dry unit weight in the mix design for the depth of treatment specified. Provide mix designs that establish acceptable tolerances for cement, water, additives and corrective aggregate to allow mix adjustments during production. Ensure the mix design includes details on soil/aggregate gradation, cementitious material, compressive strength, and density to be achieved during compaction.

306.02.02 Equipment

Provide equipment as specified:

Bituminous Material Distributor………………………………………………………………………………………1003.07

Cement Spreaders…………………………………………………………………………………………………………….1012.01

Reclaimer/Stabilizer..………………………………………………………………………………………………………..1012.02

Motor Grader..………………………………………………………………………………………………………………….1008.07

Pneumatic-Tired Compactor..……………………………………………………………………………………………1002.01

Dynamic Compactor..………………………………………………………………………………………………..………1002.02

Steel Wheel Roller..…………………………………………………………………………………………………………..1002.03

Padfoot Roller..………………………………………………………………………………………………………………….1002.04

Water Truck…..…………………………………………………………………………………………………………………..1008.08

Provide a nuclear density gauge conforming to ASTM D 6938

306.03 CONSTRUCTION

306.03.01 Full Depth Reclamation, Cement Stabilized

A. Roadway Preparation. Remove crack filler, raised pavement markers, loop wires, thermoplastic markers and other materials that will adversely affect the FDR mix as observed from the roadway prior to beginning the reclaiming process. Survey and protect from damage manholes, inlets, valve covers, and other buried structures and utilities prior to processing.

B. Weather Limitations. Do not construct FDR when the soil, aggregate or subbase is frozen, or when the ambient temperature is below 40°F or when freezing temperatures are anticipated within 7 days of the end of the FDR placement. Do not construct FDR when the existing base course or subbase contains excessive moisture or when high winds may displace the application of dry cement.

C. Control Strip. During the first day of production, construct a control strip to verify that the construction process meets the specified requirements. Ensure the control strip is at least 500 feet in length and adequate size for the Contractor to:

1.  Demonstrate that the equipment, materials, and processes proposed can produce a reclaimed material layer that conforms to the specifications.

2.  Adjust the rates for cement, water, and any additives recommended for the reclaimed material.

3.  Determine the roller pattern necessary to obtain the density requirements.

4.  Obtain representative samples for moisture, density and compressive strength testing

The Contractor may continue FDR operations through the first day if the Contractor’s equipment and process meet the specifications. Suspend operations and submit a plan for corrective action if the specifications are not achieved. Do not continue FDR operations beyond the first day unless a control strip has been approved by the RE. Rework, re-compact, or remove and replace FDR control strips and FDR production areas that do not meet the specifications. Upon acceptance of the control strip by the RE, use the same equipment, materials, and construction methods for the remainder of FDR operations. If adjustments are necessary, submit a request to the Department for approval and construct a new control strip to demonstrate satisfactory results.

D. Corrective Aggregate. When required by the design, use corrective aggregate that consists of coarse aggregate, RAP or a combination of coarse aggregate and RAP that meets the requirements in table 306.03.01-1. Uniformly spread and grade corrective aggregate on the roadbed with equipment except in limited or restricted areas where the use of hand spreading is allowed. Place aggregate either prior to pulverization or following pulverization but prior to the addition of cement and mixing. If applied following pulverization, blend the granular material with the reclaimed material by means of additional full depth mixing to form a homogeneous mixture prior to the application of cement.

E. Pulverization. Pulverize the pre-determined full depth of HMA, base course and/or subbase soils to the depth specified using a reclaimer/stabilizer. Ensure the material is pulverized to a homogenous mixture with the specified gradation. Ensure the optimum moisture content during this process by means of surface application or through the reclaimer/stabilizer integrated fluid injection system.

Construct pulverization in a series of parallel lines to minimize longitudinal and transverse joints. Overlap longitudinal joints between successive cuts a minimum of 6-inches and overlap transverse joints a minimum of 2-feet.

When a paving fabric is encountered during the pulverizing operation, make the necessary changes in equipment or operations so that incorporation of the shredded fabric into the reclaimed material does not affect the performance parameters or inhibit placing or compaction of the FDR stabilized base. Remove and properly dispose of oversized pieces of paving fabric greater than `3 inches in any dimension.

Residual materials that cannot be completely removed from the processed materials may be incorporated if the contractor can demonstrate that those added materials will not adversely affect the FDR stabilized base course. Ensure any such materials retained in the mix are appropriately sized and blended and do not adversely affect the performance of the FDR stabilized base. Ensure the processed (pulverized) material meets the following gradation:

Table 306.03.01-1 Gradation Requirements for Pulverized Material
Sieve Size / Minimum Percent Passing
3" / 100
2" / 95
No. 4 / 55

Remove and dispose of excess material, if required, prior to cement application. Ensure that the surface of the pulverized pavement is at elevations that when mixed with cement and water and re-compacted to the required density, conform to the elevations shown on the Plans, or as directed by the RE.

F. Cement Application and Mixing. Use dry cement for FDR. Provide an approved spreader/distributor to ensure that the specified quantity of cement is uniformly applied. Apply and mix cement in a series of parallel lines to minimize longitudinal and transverse joints. Ensure that no traffic other than the reclaiming equipment is allowed to pass over the spread cement or any corrective aggregate until the reclaiming operation is complete. Overlap longitudinal joints between successive passes a minimum of 3-inches and overlap transverse joints a minimum of 2-feet. Apply cement to within a tolerance of +/- 5% of the rate required by the mix design. Use multiple passes as necessary to ensure the proper amount of cement is applied.

Spread cement in a manner that minimizes dust. Reduce the distance between the spreader and the reclaiming operation appropriately during windy days; suspend operations when dry cement is displaced by wind. Use dust control measures to minimize fugitive dust.

Ensure that the water application is through the reclaimer/stabilizer integrated fluid injection system during mixing. Perform mixing while introducing water into the pulverized material through the metering device on the mixer.

Ensure that the time from cement placement to start of mixing does not exceed 30 minutes.

If necessary, add water to the pulverized material during mixing to provide a moisture content not less than 1 percent below nor more than two percent above (-1 to +2 of OMC) the optimum moisture content of the cement mixture (ASTM D 558) to ensure chemical action of the cement stabilizer and processed materials. Continue mixing until the entire mixture, RAP, base course and/or subbase soil is uniform in color, meets the gradation requirements and is at the required moisture content throughout. Make adjustments to cement, water, and additives as required ensuring a reclaimed mixture that conforms to the density and compressive strength requirements. Record and submit all adjustments to the Department.

Perform quality control checks at a minimum of every 1000 feet for gradation, moisture and thickness at the conclusion of mixing operations. Report results to the RE. Ensure the entire operation of cement spreading, water application and mixing results in a uniform pulverized base, cement and water mixture for the full depth and width specified. The RE or ME may reject or require additional mixing of any sections rendered non-uniform in color, with particles not coated with cement, not meeting gradation or not at the required moisture content throughout. Visual inspection of the material, review of gradation and moisture by the RE or ME are considered sufficient grounds for such rejection.

If the measured thickness deviates by plus or minus ½ inch from that specified, reconstruct or replace the base course. Fill test holes with base course material and compact to the required density.

Uniformly treat areas around inlets, manholes, utility risers, valves and adjacent to curbs/gutters or in corners that are inaccessible to the reclaimer/stabilizer. Excavate the material to the depth of treatment and place where it is accessible to be mixed, then replace and compact following proper mixing.

G. Compaction. Immediately after cement application and mixing, shape the road with a motor grader and compact with a steel roller to provide better depth control. Ensure that compaction begins no more than 20 minutes after mixing or immediately upon achieving gradation and moisture requirements. Complete all compaction operations within 2 hours from start of mixing operations. Ensure no section is left undisturbed for more than 30 minutes during compaction operations. Uniformly compact the mixed material in one layer to a minimum of 98% of the maximum dry density as determined by ASTM D 558 during the mix design. Acceptance is based on a moving average of five consecutive tests with no test below 96%. Determine dry density based on wet density determined by AASTHO T 310 and moisture content determined by laboratory testing using ASTM 4643 or ASTM 4959. Report results to the RE and ME. The RE or ME will take random samples and test to verify quality control test results and conformance with the requirements.

H. Finishing and Surface Tolerance. As compaction nears completion, shape the surface of the FDR stabilized base to the specified lines, grades and cross sections. If necessary, lightly scarify or broom-drag the surface to remove equipment imprints or to prevent compaction planes. Continue compaction until the surface is uniform and the specified density is obtained. Ensure the surface is kept moist during the finishing process by means of water spray devices that do not erode the surface. Perform compaction and finishing in a manner that produces a surface free of compaction planes, cracks, ridges or loose material. Ensure the surface does not vary more than a tolerance of ½-inch using a 10-foot straight edge placed on the surface. Correct humps exceeding this tolerance by trimming, milling or abrasive grinding. Feathering is not permitted for repair of low areas. Complete all finishing operations within 4 hours from start of mixing except that trimming (cuts only) must be completed within 24 hours of mixing.

I. Curing. After completion of final finishing, cure the cement stabilized surface by application of asphalt emulsion tack coat, or maintain continuously moist for a period of 7 days with a water spray that will not erode the surface of the FDR stabilized base. If curing material is used, apply as soon as possible, but not later than 24 hours after completing finishing operations. Ensure the surface is maintained continuously moist prior to application of the asphalt emulsion.

For bituminous curing membranes ensure the FDR stabilized base is free of all loose extraneous materials and applied tack coat conforming to 401.03.02.

J. Traffic. Completed portions of FDR stabilized base can be opened immediately to low speed local car traffic and to construction equipment, provided the curing material or moist curing is not impaired and provided the FDR base course is sufficiently stable to withstand marring or permanent deformation. Do not leave any dry cement exposed at the end of the workday. Protect finished portions of the FDR stabilized base to prevent equipment from marring or damaging completed work that are traveled on by construction equipment used in constructing an adjoining section. Prevent heavy trucks from traveling on the stabilized base until the final surfacing is placed, and/or a proof roll has passed. Perform proof rolling to represent the type of traffic expected on the pavement. If deformation does not occur, the RE may allow low volumes of truck traffic before the final surfacing is placed. If deformation does occur, ensure truck traffic is kept off until the stabilized base has hardened sufficiently to prevent marring or permanent deformation.

K. Maintenance. Maintain the surface of the FDR stabilized base in a condition suitable for the safe movement of traffic. Protect and maintain the surface from runoff water, other deleterious substances, and/or any other damage. Repair any damage to the completed FDR stabilized base prior to the placement of the final surfacing. If it is necessary to replace any processed material, replace for the full depth, with vertical cuts, using an approved material. Skin patches are not permitted.

Correct depressions exceeding the specified depth tolerance by applying tack coat and filling with HMA just prior to placement of the final surfacing.

Place subsequent pavement layers when the FDR stabilized base has cured for a minimum of 7 days and is sufficiently stable to support the required construction equipment without marring or permanent distortion of the surface.