Section 305 — Full Depth Reclamation with Cement
Description
305.01This work consists of pulverizing an existing pavement and base in- place, adding crushed aggregate if required, mixing this material with cement and water, and shaping and compacting the mix to produce a stabiliz ed base.
Material
305.02Conform to the following Subsections: Crushed aggregate 703.06 Hydraulic cement 701.01 Water for construction 725.01(c)
Construction Requirements
305.03Proportioning. Collect representative samples of the pavement and base from the project. Process and blend these materials to achieve a gradation representative of the in -place pulverized material. Estimate the median ceme nt content by percent of total mix weight to meet the requirements shown in Table 305-1 . At this median cement content and at cement contents 1 or 2 percent above and below this median, determine the optimum moisture content, maximum density, and the parameters shown in Table 305-1. Choose range of cement contents to properly bracket the strength requirements shown in Table 305-1. Table 305-1 Soil-Aggregate- Cement Mix Design Parameters
Property Requirement
Unconfined compressive strength,
ASTM D1633, Method A(1) Average strength range (3 specimens) 200 to 400 psi Maximum strength of a single specimen break 500 psi or less Loss in mass, AASHTO T 135 & T 136 , 12 cycles 14% maximum
(1)At 7-day cure at 70 °F according to ASTM D1632. Submit a mix design for approval at least 14 days before production which includes the following:
(a)Optimum cement content conforming to the requirements shown in Table 305-1;
(b)Maximum density and moisture content at the optimum cement content according to AASHTO T 134, at least 5 points;
(c)Source of cement and imported crushed aggregate including certifications;
(d)Results of tests and applicable charts and graphs;
(e)Gradation and proportion of imported crushed aggregate;
(f)Proportion of base material to pavement and gradation of the mix;
(g)200-pound sample of the pavement, base, and imported crushed aggregate, if requested; and
(h)20-pound sample of portland cement, if requested. Start production only after the mix design is approved. If the mix design is rejected, submit a new mix design for approval.
305.04General. Establish existing pavement cross- section according to Subsection 152.05. Maintain the established cross-section or construct to proposed cross-section. Protect manholes, valve covers, and other buried facilities from damage.
305.05Producti on Start -Up Procedures. If an asphalt overlay is required, do not start FDR production until the asphalt overlay mix design has been approved.
(a)Preparatory phase meeting. Conduct a pre -stabilization preparatory phase meeting according to Subsection 153.06(a) at least 7 days before the start of stabilizing operations . Before the preparatory phase meeting, convert the approved mix design cement percentage to pounds per square yard and submit to the CO.
(b)Control strip. Provide 7 days’ notice before starting production. On the first day of production, stabilize a 1000-foot control strip, one- lane wide, at the designated lift thickness and mix design proportions. Construct the control strip on the project at an approved location. Constr uct the control strip using construction procedures intended for the entire project. Take nuclear gauge density readings behind each roller pass to determine the roller pattern necessary to achieve the specification requirements in Subsection 305.10. Cease production after construction of the control strip until the stabilized base and the control strip are evaluated for acceptance. Repeat the control strip process until an acceptable control strip is produced. See Subsection 106.01 for the disposition of material in rejected control strips. Accepted control strips may remain in place and will be accepted and measured as a part of the completed base. When a control strip is accepted, full production may start. Use these start -up procedures when changing construction procedures, when resuming production after a termination of production due to unsatisfactory quality according to Subsection 106.04, or the starting of a new construction season.
305.06Add ing Crushed Aggregate. Conform to Subsection 304.04.
305.07Pulverizing. Conform to Subsection 304.05.
305.08Applying Cement. Do not add cement when the underlying surface is frozen, muddy, or when conditions allow for excessive loss to eroding or blowing. Start cement application when the air temperature is above 40 °F and is expected to stay above 40 °F for 48 hours. Apply cement by one of the following methods:
(a)Dry method. Use a metered mechanical spreader to uniformly apply the cement. Use canvas (or similar) skirts around the spreader box to minimize dust.
(b)Slurry method. Use approved equipment and dispersal processes to uniformly apply a cement and water slurry without pooling or run off. Equip slurry tanks with an agitator to keep the cement suspended in water. Apply the slurry to the pulverized material with 60 minutes from time water first contacts the cement. Make successive passes over the material if necessary to obtain the proper moisture and cement content for mixing and compacting.
305.09Mixing. Start mixing within 30 minutes after cement application. Use a road reclaimer conforming to Subsection 304.05. Add water as necessary to adjust the moisture content of the mixture to within 2 percent of optimum as indicated in the approved mix design. Continue mixing until the cement is uniformly distributed within the in situ material creating a homogeneous full depth layer. Complete mixing within 1 hour of the cement application.
305.10Compacting and Finishing. Compact the processed material uniformly to at least 95 percent of maximum density as determined from AASHTO T 134. Provide rollers sized and configured to achieve the required compaction and finishing. Operate rollers according to the manufacturer’s recom mendations. Compact the processed material full width by rolling from the sides to the center, parallel to the centerline of the road. Along curbs, headers, walls, and places not accessible to the roller, compact the material with approved tampers or compa ctors. During compaction and final grading maintain the moisture content of the mixture to within 2 percent of optimum. Do not leave areas of stabilized material uncompacted or undisturbed for more than 30 minutes. Complete compaction within 1 hour after mixing. Finish the compacted surface according to Subsection 301.06 to produce a surface that is smooth, dense, and free of compaction planes, ridges, or loose material. Clean the compacted surface of loose material, dirt, o r other deleterious material by approved methods. Complete finishing operations within 4 hours from the start of mixing including corrections to irregularities in the surface.
305.11Construction Joints. If cement application operations are delayed or stopped for more than 2 hours, make a transverse construction joint by cutting back into the completed work to form an approximately vertical face. Tie new work into the completed work by remixing approximately 36 inches of the completed course.
305.12Micro- cracking. Micro -crack the finished compacted surface 48 to 72 hours after completion of compaction using a minimum 10- ton vibratory steel drum roller, set at maximum amplitude, advancing at approximately 3 feet per second, and make three full passes, or as approved.
305.13Curing. Allow material to cure at least 24 hours before placing the next course. Cure by one of the methods below:
(a)Water method. Keep the surface continuously moist by applying water through a spray bar equipped with nozzles producing a fine, uniform spray. During the first 24 hours of curing, use a water truck with side spray to avoid driving on the newly stabilized layer. P revent damage to the finished surface. Maintain a moist surface until next course is placed.
(b)Prime coat method. Seal the surface by placing an inverted prime coat according to Subsection 411.06(b) . Provide and maintain a continuous film over the surface. Apply prime coat within 72 hours after compacting and finishing. Keep surface moist a ccording to Subsection 305.13(a) until prime coat is placed. Do not allow traffic and construction equipment on stabilized base until it is sufficiently stable to withstand marring and permanent deformation. Restrict traffic according to Section 156. Limit traffic speeds to 20 miles per hour.
305.14Maintenance. Maintain the cement stabilized layer to the correct line, grade, and cross -section until placement of the next course. If the cement stabilized layer loses stability, density, or finish before placement of the next course, reprocess, recompact, and add cement as necessary to restore the strength of the damaged material. Overlay the stabilized base within 14 days after completing finishing operations according to Subsection 305.10.
305.15Acceptance. See Table 305-2 for sampling, testing, and acceptance requirements. Crushed aggregate will be evaluated under Subsections 106.02 and 106.03. Cement will be evaluated under Subsections 106.02 and 106.03. Construction of full depth reclamation with cement will be evaluated under Subsections 106.02 and 106.04. Prime coat will be evaluated under Section 411.
Measurement
305.16Measure the Section 305 pay items listed in the bid schedule according to Subsection 109.02 .
Payment
305.17The accepted quantities will be paid at the contract price per unit of measurement for the Section 305 pay items listed in the bid schedule. Payment will be full compensation for the work prescribed in this Section. See Subsection 109.05 . Table 305-2 Sampling, Testing, and Acceptance Requirements
Material or
Product
Type of
Acceptance
(Subsection) Characteristic Category Test Methods
Specifications Sampling
Frequency Point of
Sampling Split
Sample Reporting
Time Remarks
Mix Design
Full depth
reclamation (FDR) with cement mixture Measured & tested for conformance (106.04 ) All – Subsection
305.031 per submitted mix design Existing roadway Yes 14 days minimum before production – Production Start -up (control strip)
FDR with
cement material Measured & tested for conformance (106.04 ) Gradation − AASHTO T 27 3 minimum Behind reclaimer before compaction No Upon
Completion
of test Minus 1½-in sieve requirement only
Moisture -
density (maximum density) – AASHTO T 134 1 minimum " Yes " 5 points per proctor minimum
Moisture
content (in-place) – AASHTO T 255 3 minimum In-place after compaction No " − Density − AASHTO T 310 or other approved methods Subsection 305.05(b) " " " − Table 305- 2 (continued) Sampling, Testing, and Acceptance Requirements
Material
or
Product Type of
Acceptance
(Subsection) Characteristic Category Test Methods
Specifications Sampling
Frequency Point of
Sampling Split
Sample Reporting
Time Remarks
Production
FDR with
cement material Measured & tested for conformance (106.04 ) Moisture - density (maximum density) – AASHTO T 134 1 per change of material Behind reclaimer before compaction Yes Before using in work 5 points per proctor minimum Density – AASHTO T 310 or other approved procedures 1 per 2000 yd2 In-place after compaction No End of shift –
Process
control (153.03 ) Gradation – AASHTO T 27 1 per 3500 yd2 minimum Behind reclaimer before compaction " Upon completion of test Monitor percent passing the 1½-in & No. 4 sieves
Moisture
content (in-place) – AASHTO T 255 or other approved methods " In-place after compaction " " −
Unconfined
compression strength (7-day) – Table 305-1 1 per day minimum Behind reclaimer before compaction " 7 days 7-day cure
Finished Product
FDR with
cement material Measured & tested for conformance (106.04 ) Surface tolerance & grade – Subsection
301.06As directed Completed
FDR
surface No Before placement of next layer or as requested −