SECTION 306: PORTLAND CEMENT OR LIME TREATED SUBGRADE
306.1 Description
This Work consists of the following: 1. Preparing the Roadbed; 2. Providing, applying, mixing, and processing Portland Cement or Lime; and 3. Compacting the mixture.
306.2 Materials
306.2.1 Portland Cement Treated Subgrade
The Contractor shall provide Portland cement in accordance with Section 509, “Portland Cement Concrete Mix Designs” or Section 510, “Portland Cement C oncrete.”
306.2.2 Lime Treated Subgrade
306.2.2 1 Hydrated Lime
The Contractor shall provide hy drated lime in accordance with A ASHTO M 216. When dry sieved in a mechanical shaker for ten (10) min ± 30 s, a 0. 5 lb test sample of hydrated lime shall conform to the gradation requirement in Table 306.2.2.1:1 , “Hydrated Lime Gradation Requirements.” Table 306.2.2.1:1 Hydrated Lime Gradation Requirements Sieve size % passing No. 30 97.0 – 100.0 No. 200 75.0 – 97.0
306.2.2 2 Quicklime
The Contractor shall provide quicklime in accordance with AASHT O M 216. When dry sieved in a mechanical shaker for ten (10) min, ± 30 s, ensure a 0.5 lb test sample of quicklime is in accordance with Table 306.2. 2.2:1, “Quicklime Gradation R equirements.” Table 306.2.2.2:1 Quicklime Gradation Requirements Sieve size % passing 3/4 inch 95 – 100 No. 100 0 – 25
306.2.2 3 Lime-Slurry
The Contractor shall provide lime-slurry as a suspension of sol ids in water that can be pumped. The water or liquid portion of the slurry is free of d issolved material. Lime-slurry shall be a mixture of quicklime and water. The hydrated lime s olids in the mixture shall meet the following requirements: 1. Chemical Composition. Lime-slurry with a “solids content” of at least 90% (by weight) calcium and magnesium oxides; 2. Residue. Lime-slurry mixture with a retained “solids content” residue i n Section 306: Portland Cement o r Lime Treated Subgrade Page 136 accordance with Table 306.2.2.3:1, “Lime Slurry 'Solids Content ' Gradation Requirements;” and Table 306.2.2.3:1 Lime-Slurry “Solids Content” Gradation Requirements Sieve size % passing No. 4 99 – 100 No. 30 96 – 99 3. Grade. Provide lime-slurry with a minimum “dry solids content,” of 35 %.
306.3 Construction Requirements
306.3.1 Subgrade Preparation
The Contractor shall treat the Subgrade with either Portland ce ment or hydrated lime; quicklime, or lime-slurry in accordance with the State Material s Bureau’s mix design. The Contractor shall identify and correct soft areas, then shap e the subgrade to the grades shown in the plans before adding Portland cement or hydr ated lime, quicklime, or lime- slurry. The Contractor shall ensure that the scarified depth o f the treated Subgrade (shown in the Plans) is free of Deleteri ous Material and stones retained on a three (3.0) inch sieve. The Contractor shall: 1. Not perform Work during wet or inclement weather. 2. Mix and place the Portland cement-treated or lime-treated Su bgrade, only if when the air temperature is at leas t 40 °F and rising in the shade. 3. Not mix or place cement-treated or lime-treated Subgrade on frozen Subgrade. When the air temperature is forecast to fall below 32 °F within a 48-hour period, the Contractor shall cease Work or ensure the Subgrade temperature will not fall below 40 °F. 4. Proof-roll the Material with Equipment, approved by the Proj ect Manager, to expose and correct the soft areas. Where unstable Subgrade is encount ered in cuts or existing grad es, due to no fault or neglect of the Contractor, sub-excavation and borrow will be pa id for and measured as per Section 203, “Excavation, Borrow, and Embankment.” Engineered designs will be measured and paid for on an item by item basis or as specified in the Co ntract. The Contractor shall conduct operations in such a way that the Project Manager can t ake the necessary cross- sectional measurements before the backfill is placed.
306.3.2 Portland Cement Treated Subgrade
Prior to the addition of Portland cement, the Contractor shall pulverize the Subgrade to the specified depth so that at least 80% (by weight) passes thr ough a No. 4 sieve. The Contractor shall: 1. Apply Portland cement at the specified application rate and to the depth shown on the Plans or as indicated on the State Materials approved mix d esign. 2. Ensure that cement dust is not a hazard to the public or wor kers when processing the Portland cement-treated Subgrade. Section 306: Portland Cement o r Lime Treated Subgrade Page 137 3. Perform mixing, placing, compacting, and finishing on the sa me day as the cement placement.
306.3.2 1 Mixing
The Contractor shall mix the portland cement, soil, and water w ith a self-propelled rotary- type mixing machine (approved by the Project Manager) to provid e a uniform mixture. Overlap at least six (6) inches between passes. The Department will consider streaks and pockets of portland ce ment as evidence of unacceptable mixing. The Contractor shall ensure the Material moisture content range s between optimum to five percent (5%) over optimum within the entire treated depth.
306.3.2 2 Finishing Operations
The Contractor shall: 1. Compact to 95% maximum density in accordance with AASHTO T 1 80 (Modified Proctor), Method D (TTCP Modifi ed), immediately after mixing is complete. 2. Finish to ± 0.1 ft along centerline and ± 0.05 ft at right a ngles to the centerline. 3. Correct deviations from these tolerances. 4. Final roll the surface to finish the completed Work and pre vent hairline cracking. 5. Finish within four (4) h of adding the Portland cement. The Contractor shall allow the cement-treated Subgrade to cure for at least seven (7) Days before placing Base Course or Subbase Material on top of t he cement-treated Subgrade or as approved by the Project Manager. Maintain a moist, not s aturated, condition during the entire curing period, to prevent drying. If permitted by local jurisdiction, the Contractor may use an alternate curing procedure by applying a CSS-1 or SS-1 e mulsified asphalt to the surface so that the surface is fully covered and sealed, as app roved by the Project Manager.
306.3.3 Lime Treated Subgrade
The Contractor shall: 1. Use a distributor that will apply a uniform application and automatically adjust the spread rate for variable travel speeds. 2. Apply hydrated lime or quicklime dry, within ±0.5% of the s pecified percentage, by weight shown on the Plans or as indicated on the State Material s approved mix design, onto the prepared scarified Subgrade. 3. Not use a tailgate spreader. When used, the Contractor shal l apply quicklime at the equivalent percentage to hydrated lime (one (1.0) ton quicklime is equivalent to 1.3 tons hydrated lime). 4. Apply lime-slurry, at the specified percentage of dry solids content onto the prepared scarified Subgrade, with a distributor having a pump and a spra y bar. 5. Continuously circulate the slurry in transit and during appl ication. The Contractor shall apply the lime-slurry within 24 h of its production. Aft er 24 h, the slurry is considered expired. 6. Dispose of the expired slurry in an environmentally-acceptab le manner, and shall not use it on the Project. 7. Replace lime-slurry that is left exposed on the ground to th e open air for more than Section 306: Portland Cement o r Lime Treated Subgrade Page 138 ten (10) hours and shows excessive moisture loss.
306.3.3 1 Initial Mixing
The Contractor shall: 1. Process the hydrated lime, quicklime, or lime-slurry so as n ot to present a hazard to the public or workers. 2. Mix the Material immediately after applying the lime treatme nt using a self-propelled rotary-type mixing machine. 3. Provide a loose uniform mixture, with clods and lumps no lar ger than two (2) inch, that, when compacted, will meet t he required depth and width sh own in the Plans. The Contractor shall overlap a t least six (6) inches between pa sses. The Department will consider visible streaks and pockets as evi dence of unacceptable mixing. Immediately following mixing, the Contractor shall ensure the e ntire treated Subgrade depth’s moisture content is three percent (3%) to five percent (5%) above optimum in accordance with AASHTO T 180 (Modified Proctor), Method D (TTCP Modified). Lightly compact the surface to minimize water loss or gain and lime car bonation.
306.3.3 2 Curing
The Contractor shall allow the treated lightly compacted Subgra de to cure for at least 24 h. Apply a seal during the cure period using either: 1. A water curing seal that mai ntains moisture content at not l ess than three percent (3%), or more than five percent (5%) above optimum as determine d by AASHTO T 180 (Modified Proctor), Method D (TTCP Modified); or 2. An SS or CSS emulsified asphalt seal using a rate between 0. 10 to 0.20 gal per square yard as determined by the Project Manager. Treated Subgrade temperature must remain above 40 °F during the entire curing period.
306.3.3 3 Final Mixing
The Contractor shall ensure, b y additional pulverization, that the stabilized lime-soil mixture meets the requirements of Table 306.3.3.3:1, “Lime-Trea ted Subgrade Gradation Requirements” before final compaction. Table 306.3.3.3:1 Lime-Treated Subgrade Gradation Requirements Sieve size % passing One (1) inch 100.0 No. 4 60.0 – 100.0
306.3.3 4 Finishing Operations
The Contractor shall: 1. Compact the treated Subgrade, immediately after final mixing is complete, to 95% of the maximum density in accordance with AASHTO T 180 (Modified P roctor), Method D (TTCP Modified). The Project Manager will verify the compact ed depth of lime- treated Subgrade with a Contractor-provided phenolphthalein ind icator chemical or Section 306: Portland Cement o r Lime Treated Subgrade Page 139 beet juice. 2. Finish the treated Subgrade to ± 0.1 ft along the centerline and ± 0.05 ft at right angles from centerline. 3. Lightly roll the completed se ction to prevent hairline crack ing.
306.3.4 Protection of Treated Subgrade
The Contractor shall: 1. Allow only sprinkling or spraying Equipment, on the treated subgrade during the curing period, unless otherwise approved by the Project Manager . 2. Install a base, Sub-base, or wearing surface before opening the Roadway to the public, unless otherwise approved by the Project Manager.
306.4 Method of Measurement
The Department will pay for lime as Hydrated Lime using the fol lowing conversion: 1. One (1) ton of quicklime equals 1.3 ton of hydrated lime.
306.5 Basis of Payment
Pay Item Pay Unit Cement-Treated Subgrade Square Yard Portland Cement Ton Lime Treated Subgrade Square Yard Hydrated Lime, per Section 402 Ton
306.5.1 Work Included in Payment
The Department will consider as included in the payment for th e pay item(s) listed in this section and will not measure or pay separately for the followin g Work: 1. Preparing the Roadbed; 2. Providing, applying, mixing and processing Portland Cement o r Lime and compacting the mixture; 3. Correcting soft areas and reshaping the subgrade before addi ng cement or lime; and 4. Ensure scarified depth of the treated subgrade (shown in the plans) is free of deleterious material and stones retained on three (3.0) inch si eve. Division: 400 Page 140 DIVISION 400 – SURFACE TREATMENTS AND PAVEMENTS
Division C — ontents
401: Pavement Smoothness Measurement .......................... ......... 141 402: Asphalt Materials and Mineral Admixtures ................. ............ 153 403: Open Graded Friction Course .............................. .................. 162 405: Detour Pavements ......................................... ......................... 169 407: Tack Coat ................................................ ............................... 172 408: Prime Coat ............................................... .............................. 174 411: Hot-Poured Crack Sealant ................................. .................... 177 412: Hot In-Place Recycling O f Asphalt Pavement (Remixing Method) ...................................................... .................................... 180 413: Single-Machine Hot In-Place Surface Repaving ............. ....... 185 414: Cold Milling ............................................. ................................ 191 415: Pavement Surface Restoration ............................. ................. 193 416: Minor Paving ............................................. ............................. 201 417: Miscellaneous Paving ..................................... ........................ 205 423: Hot Mix Asphalt (HMA) (Major Paving) ..................... ............. 209 424: Warm Mix Asphalt (WMA) (Major Paving) .................... .......... 229 450: Portland Cement Concrete Pavement (PCCP) (QLA) ........... . 234 451: Portland Cement Concrete Pavement (PCCP) (Non-QLA) .... 25 2 452: Sealing and Resealing Concrete Pavement Joints ........... ..... 255 454: Cracking and Seating Concrete Pavement ................... ......... 258 455: Diamond Grinding and Diamond Grooving of Portland Cement Concrete Pavement (PCCP) ..................................... ..................... 260 Division: 400 Page 140 DIVISION 400 – SURFACE TREATMENTS AND PAVEMENTS
Division C — ontents
401: Pavement Smoothness Measurement .......................... ......... 141 402: Asphalt Materials and Mineral Admixtures ................. ............ 153 403: Open Graded Friction Course .............................. .................. 162 405: Detour Pavements ......................................... ......................... 169 407: Tack Coat ................................................ ............................... 172 408: Prime Coat ............................................... .............................. 174 411: Hot-Poured Crack Sealant ................................. .................... 177 412: Hot In-Place Recycling O f Asphalt Pavement (Remixing Method) ...................................................... .................................... 180 413: Single-Machine Hot In-Place Surface Repaving ............. ....... 185 414: Cold Milling ............................................. ................................ 191 415: Pavement Surface Restoration ............................. ................. 193 416: Minor Paving ............................................. ............................. 201 417: Miscellaneous Paving ..................................... ........................ 205 423: Hot Mix Asphalt (HMA) (Major Paving) ..................... ............. 209 424: Warm Mix Asphalt (WMA) (Major Paving) .................... .......... 229 450: Portland Cement Concrete Pavement (PCCP) (QLA) ........... . 234 451: Portland Cement Concrete Pavement (PCCP) (Non-QLA) .... 25 2 452: Sealing and Resealing Concrete Pavement Joints ........... ..... 255 454: Cracking and Seating Concrete Pavement ................... ......... 258 455: Diamond Grinding and Diamond Grooving of Portland Cement Concrete Pavement (PCCP) ..................................... ..................... 260 Section 401: Pavement Smoothness Measurement Page 141