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Home / DOT Specifications / New Mexico / 2019 NMDOT Standard Specifications for Highway & Bridge Construction / 306
Bases (300-399)

306Portland Cement or Lime Treated Subgrade

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306.1DESCRIPTION

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.

306.2MATERIALS

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 limes 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 %.

306.3CONSTRUCTION REQUIREMENTS

306.3.1 Subgrade Preparation The Contractor shall treat the Subgrade with either Portlandce ment or hydrated lime; quicklime, or lime-slurry in accordance with the State Materials 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 hydrated 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 grades, 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 portlandce ment as evidence of unacceptable mixing.

The Contractor shall ensure the Material moisture content ranges 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 Modified), 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, nots 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 Materials 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. After 24 h, the slurry is considered expired.

6.Dispose of the expired slurry in an environmentally-acceptable 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 compacted 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 completedse ction to prevent hairline cracking.

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.

306.4METHOD 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.

306.5BASIS 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 Contents

412: Hot In-Place Recycling O f Asphalt Pavement (Remixing 450: Portland Cement Concrete Pavement (PCCP) (QLA) ........... . 234 451: Portland Cement Concrete Pavement (PCCP) (Non-QLA) .... 25 2 455: Diamond Grinding and Diamond Grooving of Portland Cement Division: 400 Page 140 DIVISION 400 – SURFACE TREATMENTS AND PAVEMENTS

Division Contents

412: Hot In-Place Recycling O f Asphalt Pavement (Remixing 450: Portland Cement Concrete Pavement (PCCP) (QLA) ........... . 234 451: Portland Cement Concrete Pavement (PCCP) (Non-QLA) .... 25 2 455: Diamond Grinding and Diamond Grooving of Portland Cement Section 401: Pavement Smoothness Measurement Page 141

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Source: New Mexico Standard Specifications for Highway and Bridge Construction, 2019 Edition. View official source ↗
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