24 STABILIZED SOILS
24-1 General
24-1.01 General
24-1.01A Summary
24-1.01B Definitions
stabilizing agent: Material added to improve strength and durability of the basement material.
24-1.01C Submittals
24-1.01C(1) General
At least 15 days before starting soil stabilization activities submit the name of the laboratory you will use for QC tests. The laborator y must be qualified under the Department's Independent Assurance Program. Before performing QC sampling and testing, submit the time and location the sampling and testing will occur. Submit QC testing results within 24 hours of receiving the results. Submi t a certificate of compliance with the stabilizing agent samples that includes a statement certifying the stabilizing agent furnished is the same as on the Authorized Material Source List for the stabilizing agent specified. Submit a weighmaster certificat e for stabilizing agent remaining on hand after completion of the work. Submit a stabilized soil quality control plan.
24-1.01C(2) Samples
From 30 to 180 days before use, submit one 10 lb sample of each stabilizing agent proposed and from each source. Submit stabilizing agents in airtight containers. Mark the sample date on the container. Include the SDS.
24-1.01D Quality Assurance
24-1.01D(1) General
If requested, perform QC testing in the presence of the Engineer. If required, construct test strips with materials, tools, equipment, and methods you will use in the work. Construct test pads for compaction tests by scraping away material to the depth ordered. If a compaction test fails, corrective action must include the layers of material alrea dy placed above the test pad elevation.
24-1.01D(2) Quality Control
24-1.01D(2)(a) General
Reserved
24-1.01D(2)(b) Quality Control Plan
Reserved
24-1.01D(2)(c) Qualifications
Reserved
24-1.01D(2)(d) Preparing Basement Material
After preparing an area for soil stabilization, verify the surface grades.
24-1.01D(2)(e) Mixing
Except for clods larger than 1 inch, randomly test the adequacy of the mixing with a phenolphthalein pH indicator solution.
24-1.01D(3) Department Acceptance
Stabilized soil accepta nce is based on: SECTION 24 STABILIZED SOILS
1.Visual inspection
2.Compliance with the requirements shown in the following table: Stabilized Soil Requirements for Acceptance Quality characteristic Test method Requirement Relative compaction (min, %) California Test 231 and 216 See section for the specified stabilization agenta Stabilization agent application rate Calibrated tray or equal Final application rate ordered by the Engineer ± 5% aFor lime stabilized soil, see section 24 -2.03E. For cement stabilized soil, see section 24 -3.03D.
24-1.02 Materials
24-1.02A General
Reserved
24-1.02B Water
Notify the Engineer if a water source other than potable water is used and perform testing for chlorides and sulfates. If potable water is not used, water for stabilized soil must be clean and contain no more than 650 parts per million of chlorides as Cl determined under California Test 422 and no more than 1,300 parts per million of sulfates as SO 4 determined under California Test 417.
24-1.02C Curing Seal
Curing seal must b e asphaltic emulsion, Grade SS-1, SS -1h, CSS -1, or CSS -1h.
24-1.02D Stabilizing Agent
Lime sources must be on the Authorized Material List for approved producers of lime for use in soil stabilization.
24-1.03 Construction
24-1.03A General
Do not mix dif ferent types of stabilizing agent or from more than one source. Deliver stabilizing agent in full loads unless it is the last load needed for a work shift.
24-1.03B Preparing Basement Material
For native soil and embankment other than imported borrow, remove rocks or solids larger than 1/3 of the layer thickness. Regardless of the layer thickness, remove rocks and solids greater than 4 inches. Removing soil clods is not required. Notify the Engineer if you encounter rocks or solids greater than 1/3 of the layer thickness. Removing rocks and solids is change order work. Grade the basement material to be stabilized to within 0.08 foot of the lines and grades shown.
24-1.03C Applying Stabilizing Agent
The Engineer orders the application rate as pou nds of stabilizing agent per square yard of basement material to be stabilized. Do not vary from the Engineer's ordered application rate by more than 5 percent.
24-1.03D Mixing
Stabilizing agent and basement material must be uniformly mixed at least twice to within 0.05 foot of the depth shown at any point. If you exceed the mixing depth shown by more than 10 percent, add stabilizing agent in proportion to the exceeded depth. Remix until the mixture is uniform with no streaks or pockets of stabilizing agen t.
24-1.03E Compaction
Compact using a sheepsfoot or segmented wheel roller immediately followed by steel drum or pneumatic - tired rollers. SECTION 24 STABILIZED SOILS Wherever the thickness shown is 0.50 foot or less, compact in 1 layer. Wherever the thickness shown is more than 0.50 foot, compact in 2 or more layers of approximately equal thickness. The maximum compacted thickness of any 1 layer must not exceed 0.50 foot unless you first construct a test strip to demonstrate your equipment and met hods provide uniform distribution of stabilizing agent and achieve the specified compaction. The test strip must contain at least 500 cu yd of material and no more material than 1 day's production. Construct test strips with materials, tools, equipment, an d methods you will use in the work. Use other compaction methods in areas inaccessible to rollers.
24-1.03F Finish Grading
Wherever the finished surface of stabilized soil is above the allowable tolerance, trim and remove the excess material. Do not leave loose material on the finished surface. If finish rolling cannot be completed within 2 hours of trimming, defer trimming. Finish rolling of trimmed surfaces must be performed with at least 1 complete coverage with s teel drum or pneumatic -tired rollers. Do not proceed with construction activities for subsequent layers of material until the Engineer verifies the final grades of the stabilized soil.
24-1.03G Curing
24-1.03G(1) General
Cure by one of the following methods:
1.Water cure
2.Curing seal
3.Moist material blanket
24-1.03G(2) Water Cure
Water may be used to cure the finished surface before you place a moist material blanket or apply curing seal. Keep the surface above the o ptimum moisture content of the stabilized soil. Use this method for no more than 3 days, after which you must apply a curing seal or place a moist material blanket.
24-1.03G(3) Curing Seal
Curing seal equipment must have a gauge indicating the volume of c uring seal in the storage tank. Apply curing seal to the finished surface of stabilized soil under section 37 -1.03 when the stabilized soil is at optimum moisture content and:
1.When the ambient temperature is above 40 degrees F and rising.
2.At a rate from 0.10 to 0.20 gallon per square yard. The exact rate is determined by the Engineer. Repair damaged curing seal the same day the damage occurs.
24-1.03G(4) Moist Material Blanket
Moist material blanket may be either a temporary or permanent layer of material of sufficient thickness to prevent drying of the stabilized soil. You may use moist material blanket if the stabilized soil can bear the weight of construction equipment. Maintain the moist material blanket above the optimum moisture content, as appropriate, until the next structural layer is placed.
24-1.04 Payment
The payment quantity for stabilized soil is measured from the horizontal planned surface of the stabilized soil. The payment quantity for lime or cement (cement stabilized soil) do es not include the quantity of stabilizing agent:
1.Wasted or disposed of in a manner not specified.
2.Remaining on hand after completion of the work. If you use a partial load of stabilizing agent, the quantity remaining is determined by scale weights o f the truck and the remaining stabilizing agent. SECTION 24 STABILIZED SOILS
3.Added stabilizing agent when the mixing depth exceeds the depth shown by more than 10 percent.
24-2 Lime Stabilized Soil
24-2.01 General
24-2.01A Summary
Section 24 -2 includes specifications for stabi lizing soil by mixing basement material with lime and water.
24-2.01B Definitions
mellowing period: Time between the initial and final mixing to promote initial chemical reactions between lime, water, and basement material.
24-2.01C Submittals
Submit lime samples under ASTM C50. Include the chemical and physical analyses with the submittal. At least 25 days before applying lime in slurry form, submit the slurry's lime content for authorization.
24-2.01D Quality Assurance
24-2.01D(1) General
24-2.01D(1)(a) General
Place unique, sequentially numbered lock seals on each load and affix them to trailer blowdown valves that are locked open. The bill of lading for each lime delivery must have that specific lock seal number legibly and visibly imprinted.
24-2.01D(1)( b) Preparing Basement Material
For every 500 cu yd of basement material to be lime stabilized:
1.Test the relative compaction under California Test 231
2.Test the moisture content under California Test 226
24-2.01D(1)( c) Applying Lime
The Engineer determines the final application rate for each lime product proposed from the samples submitted based on California Test 373 except each test specimen must be:
1.Compacted under ASTM D1557 , Method A or B .
2.Cured by sealing it with 2 layers of plastic at least 4 mil thick. The plastic must be tight around the specimen. Seal all seams with duct tape to prevent moisture loss. Each s ealed specimen must be placed in an oven for 7 days at 110 ± 5 degree s F. After 7 days remove the specimen from the oven and air -cool. Remove d uct tape and plastic wrap before capping. Do not soak s pecimen . Wherev er the basement material to be stabilized changes, the Engineer changes the application rate. The Engineer provides the optimum moisture content determined under ASTM D1557 for each application rate. Whenever lime in slurry form is used, report the quantit y of slurry placed by measuring the volume of slurry in the holding tank once per 40,000 sq ft stabilized soil, or twice per day, whichever is greater. The Engineer verifies the application rate of lime used in dry form with a calibrated tray, or equal, on ce per 40,000 sq ft of stabilized soil, or twice per day, whichever is greater.
24-2.01D(2) Quality Control
24-2.01D(2)(a) General
Reserved
24-2.01D(2)(b) Mixing
During mixing operations, measure and record the ground temperature at full mixing depth. Take a composite sample from 5 random locations after initial mixing. The moisture content of the composite sample tested under California Test 226 must be a minimum of 3 percent greater than SECTION 24 STABILIZED SOILS optimum. Determine the moisture versus density relationship of th e composite sample material under California Test 216, except part 2, section E, paragraph 6 is modified as follows: After adjustment of the moisture content, compact each of the remaining test specimens in the mold, then record the water adjustment, tamp er reading, and the corresponding adjusted wet density from the chart on Table 1 using the column corresponding to the actual wet weight of the test specimen compacted. Note each of these wet weights on Line I. After mixing and before compacting, determin e maximum density under California Test 216 from composite samples of mixed material samples from 5 random locations and at each distinct change in material. Test the gradation for compliance with section 24 -2.03D. Test the moisture content of the mixed material under California Test 226. Moisture content during the mellowing period determined under California Test 226 must be at least 3 percent higher than the optimum moisture content.
24-2.01D(2)(c) Compaction
Test relative compaction on a wet weight basis. After initial compaction determine the in -place density under California Test 231 and moisture content under California Test 226, at the same locations. Perform one test per 500 cu yd of lime stabilized soil. Test in 0.50 -foot depth intervals .
24-2.01D(2)(d) Quality Control Testing
Lime stabilized soil quality control must include testing the quality characteristics at the frequencies shown in the following table: QC Testing Frequencies Quality characteristic Test method Sampling location Minimum frequency Ground surface temperature before adding lime and full depth ground temperature during mixing operations --Each temperature location 1 test per 20,000 sq ft, minimum 1 per day Lime application rate Calibrated tray or equal Roadway 1 test per 40,000 sq ft, minimum 2 per day Gradation on mixed material California Test 202 Roadway 1 per 500 cu yd, minimum 1 per day Moisture content California Test 226 Roadway 1 per 500 cu yd on each layer, each day during mixing and mellowing periods, minimum 1 per day Relative compaction California Test 231 Roadway 1 per 500 cu yd on each layer, minimum 1 per day
24-2.02 Materials
Lime must comply with ASTM C977 and the requirements shown in the following table: Lime Quality Quality characteristic Test method Requirement Available calcium and magnesium oxide (min, %) ASTM C25 or ASTM C1301 and C1271 High calcium quicklime: CaO > 90 Dolomitic quicklime: CaO > 55 and CaO + MgO > 90 Loss on ignition (max, %) ASTM C25 7 (total loss) 5 (carbon dioxide) 2 (free moisture) Slaking rate ASTM C110 30 °C rise in 8 minutes SECTION 24 STABILIZED SOILS A 0.50 lb sample of lime dry -sieved in a mechanical sieve shaker for 10 minutes ± 30 seconds must comply with the percentage passing for the sieve size shown in the following table: Lime Gradation Sieve size Percentage passing 3/8" 98–100 Slurry must:
1.Be free of contaminants
2.Contain at least the minimum dry solids
3.Have uniform consistency Prepare lime slurry at the job site.
24-2.03 Construction
24-2.03A General
Before applying lime, measure the ground surface temperature. Apply lime at ground temperatures above 35 degrees F. Do not apply lime if you expect the ground temperature to drop below 35 degrees F before you complete mixing and compacting. During mixing, maintain the in -place moisture of the basement material to be stabilized at a minimum of 3 percent above the optimum moisture determined under California Test 216 as modified in section 24 - 2.01D(2)(b). During compaction and f inish grading, add water to the surface to prevent drying until the next layer of mixed material is placed, or until you apply curing treatment. Scarify the surface of lime stabilized soil at least 2 inches between each layer. Do not scarify the finished surface of the lime stabilized soil. From the application of lime to 3 days after the application of curing treatment, only equipment and vehicles essential to the lime stabilization work are allowed on the lime stabilized soil.
24-2.03B Preparin g Basement Material
Compact the basement material to at least 90 percent relative compaction.
24-2.03C Applying Lime
Apply lime in dry form. You may apply lime in slurry form, if authorized. Apply lime uniformly over the area to be stabilized using a vane spreader. Lime slurry must be in suspension during application. Apply lime slurry uniformly making successive passes over a measured section of the roadway until the specified lime content is reached. Apply the residue from lime slurry over the length of the roadway being processed.
24-2.03D Mixing
Mix lime on the same day it is applied. After the initial mixing, allow a mellowing period for at least 36 hours before final mixing. You may add water and mix during the mel lowing period. Complete all the mixing work within 7 days of the initial application of lime. Before compaction, the mixed material, except rock, must be within the percentage passing limits for the sieve sizes shown in the following table: Mixed Material Gradation Sieve size Percentage passing 1" 98–100 No. 4 60–100
24-2.03E Compaction
Do not use vibratory rollers . SECTION 24 STABILIZED SOILS Start compacting immediately after final mixing. Compact the lime stabilized soil to at least 95 percent relative compaction.
24-2.03F Finish Grading
The finished surface of the stabilized soil must not vary more than 0.08 foot above or below the grade established by the Engineer unless the stabili zed soil is to be covered by material paid for by the cubic yard, in which case the finished surface must not vary above the grade established by the Engineer. Maintain the moisture content of the lime stabilized soil at a minimum of 3 percent above optimu m moisture content through the entire finish grading operation. Wherever lime stabilized soil is below the allowable tolerance, you may use trimmed material to fill low areas only if final grading and final compaction occurs within 48 hours of beginning in itial compaction. Before placing trimmed material, scarify the surface of the area to be filled at least 2 inches deep.
24-2.03G Curing
Choose the method of curing and apply the chosen curing method within 48 hours of c ompleting the sheepsfoot or segmented wheel compaction and within the same day of any trimming and finish grading.
24-2.04 Payment
The Department does not adjust the unit price for an increase or decrease in lime quantity.
24-3 Cement Stabilized Soil
24-3.01 General
24-3.01A Summary
Section 24 -3 includes specifications for constructing CSS by mixing basement material with cement and water.
24-3.01B Definitions
Reserved
24-3.01C Submittals
Submit cement samples under California Test 125. Include the mill analysis. Submit a certificate of compliance under section 90 -1.01C(3).
24-3.01D Quality Assurance
24-3.01D(1) General
24-3.01D(1)(a) General
Stop CSS activities and immediatel y notify the Engineer if either of the following occurs:
1.Any quality control test result does not comply with the specifications
2.Visual inspection shows noncompliant CSS If CSS activities are stopped, before resuming activities:
1.Notify the Engine er of the adjustments you will make
2.Reprocess, remedy, or replace the noncompliant CSS until it complies with specifications
3.Construct a 1,000 square yard test strip of CSS demonstrating ability to comply with the specifications
4.Obtain the Enginee r's authorization
24-3.01D(1)(b) Preparing Basement Material
For every 1,000 sq yd of basement material to be cement stabilized:
1.Test the relative compaction under California Test 231
2.Test the moisture content under California Test 226
24-3.01D(1) (c) Applying Cement
The Engineer determines the final application rate based on ASTM D1633, Method A, except: SECTION 24 STABILIZED SOILS
1.Test specimens must be compacted under ASTM D1557, Method A or B.
2.Test specimens must be cured by sealing each specimen with 2 layers of pl astic at least 4 mil thick. The plastic must be tight around the specimen. Seal all seams with duct tape to prevent moisture loss. Sealed specimens must be placed in an oven for 7 days at 100 ± 5 degree s F. At the end of the curing period, specimens must b e removed from the oven and air -cooled. Duct tape and plastic wrap must be removed before capping. Specimens must not be soaked before testing. The application rate is ordered as pounds of cement per square yard of basement material to be stabilized. Before applying cement, measure and record the air temperature and in situ moisture content of the basement material to be stabilized. The Engineer verifies the application rate using a calibrated tray or equal once per 40,000 sq ft of stabiliz ed basement material, or twice per day, whichever is greater.
24-3.01D(2) Quality Control
24-3.01D(2)(a) General
Reserved
24-3.01D(2)(b) Mixing
During mixing operations, measure and record the air temperature for the basement material to be stabilized. For each day of mixing, test the in -place moisture content under California Test 231, Part 1, Section E and verify moisture content under California Test 226. Sample immediately after mixing. After mixing, maintain the in -place moisture of the basement mat erial to be stabilized within a range of 1 percent below to 2 percent above the optimum moisture determined under California Test 216. Determine in-place moisture content under California Test 231. During compaction and finish grading, add water to the sur face to prevent drying until the next layer of mixed material is placed, or until you apply curing treatment.
24-3.01D(2)(c) Compaction
After compaction, determine in -place wet density under California Test 231 and moisture content under California Test 2 26, at the same locations. Perform one test per 1,000 sq yd of CSS. Test in 0.50 -foot depth intervals from the bottom of the CSS layer regardless of the layer thickness. Convert wet density to dry density and calculate relative compaction under California Test 216 on a dry density basis.
24-3.01D(2)(d) Quality Control Testing
Cement stabilized soil quality control must include testing the quality characteristics at the frequencies shown in the following table: SECTION 24 STABILIZED SOILS QC Testing Frequencies Quality characteristic Test method Sampling location Minimum frequency Air temperature before adding cement to basement material --Each temperature location 1 test per 20,000 sq ft, minimum 1 per day Moisture content of basement material before adding cement California Test 226 Roadway 1 per 1 ,000 sq yd per layer, minimum 1 per day Cement application rate Calibrated tray or equal Roadway 1 test per 20,000 sq ft, minimum 2 per day Gradation on mixed material California Test 202 Roadway 1 per 1 ,000 sq yd per layer, minimum 1 per day Moisture content of mixed material California Test 226 Roadway 1 per 1 ,000 sq yd per layer, minimum 1 per day Moisture content of compacted material at time of relative compaction testing California Test 231 Roadway 1 per 1 ,000 sq yd per layer, minimum 1 per day Relative compaction California Test 231 Roadway 1 per 1 ,000 sq yd per layer, minimum 1 per day
24-3.02 Materials
Cement must comply with section 90 -1.02B(2).
24-3.03 Construction
24-3.03A General
Remove standing water from the basement material. Apply cement at air temperatures above 40 degrees F and rising. Do not apply cement to frozen basement material. During compaction and finish grading, add water to the surface to prevent drying until the ne xt layer of mixed material is placed, or until you apply curing treatment. Do not scarify surfaces of intermediate or final layers of CSS.
24-3.03B Applying Cement
Apply cement uniformly over the area to be stabilized using a vane spreader. Do not apply d ry cement in windy conditions that will result in dust outside the treatment area.
24-3.03C Mixing
You may mix cement and the basement material off the job site. Complete initial mixing work within 30 minutes of the a pplication of cement. After mixing, maintain the in -place moisture of the basement material to be stabilized within a range of 1 percent below to 2 percent above the optimum moisture. Before compaction, the CSS, except rock, must within the percentage passing limits for the sieve sizes shown in the following table: Cement Stabilized Soil Gradation Sieve sizes Percentage passing 2" 100 3/4" 98–100 No. 4 55–100
24-3.03D Compaction
Complete initial compaction of a layer within 2 hours of initial mixing of cement. Complete all compaction of a layer within 4 hours of mixing of cement. SECTION 24 STABILIZED SOILS Compact the CSS to at least 97 percent relative compaction.
24-3.03E Finish Grading
Maintain the moisture content of the CSS to within a range of 1 percent below and 2 percent above the optimum moisture content through the entire finish grading operation. Finish rolling of trimmed surfaces must be performed within 2 hours of completion of compacting. The finished surface of the CSS must not vary more than 0.05 foot above or below the grade established by the Engineer unless the CSS is to be covered by material paid for by the cubic yard, in which case the finished surface may not vary above the grade established by the Engineer. Fill areas of finished CSS that are lower than the grade established by the Engineer with material specified for the subsequent layer.
24-3.03F Curing
24-3.03F(1) G eneral
Choose the method of curing and apply the chosen cure method on the same day as completing compaction and any trimming and finish grading. Do not trim CSS after curing.
24-3.03F(2) Subsequent Pavement Layer
For CSS you may cure by placing a subsequent pavement layer over the finished CSS. You may place subsequent pavement layers any time after finish grading if the CSS is sufficiently stable to support the required construction equipment without marring or perma nently distorting the surface.
24-3.04 Payment
The Department does not adjust the unit price for an increase or decrease in cement quantity. The Department does not pay for subsequent layer material used to fill low areas of cement stabilized soil.
24-4 24-8 Reserved
Source: California Standard Specifications, 2024 Edition. Pages 393–402 of 1,372.