28 CONCRETE BASES
28-1 General
28-1.01 General
28-1.01A Summary
Section 28 -1 includes general specifications for constructing concrete bases .
28-1.01B Definitions
Reserved
28-1.01C Submittals
For a concrete base requiring field qualification, submit the name of your proposed testing laboratory at least 25 days before the qualification. For a base not requiring field qualification, submit the name of the proposed laboratory at least 10 days before submitting your mix design.
28-1.01D Quality Assurance
28-1.01D(1) General
Aggregate samples must not be treated with lime, cement, or chemicals before testing for sand equivalent. Stop concrete base activities and immediately not ify the Engineer whenever:
1.Any QC or QA test result does not comply with the specifications
2.Visual inspection shows a noncompliant concrete base If concrete base activities are stopped, before resuming activities:
1.Notify the Engineer of the adjus tments you will make
2.Remedy or replace the noncompliant concrete base
3.Field qualify or construct a new test strip as specified for the concrete base involved to demonstrate compliance with the specifications
4.Obtain authorization
28-1.01D(2) Qual ity Control
28-1.01D(2)(a) General
Reserved
28-1.01D(2)(b) Quality Control Plan
Reserved
28-1.01D(2)(c) Qualifications
Reserved
28-1.01D(3) Department Acceptance
Reserved
28-1.02 Materials
Aggregate must be clean and free of decomposed material, organic material, and other deleterious substances.
28-1.03 Construction
28-1.03A General
Reserved
28-1.03B Subgrade Preparation
Immediately before placing the base , verify that t he subgrade to receive the base complies with the specified compaction and elevation tolerances and is:
1.Free of loose and extraneous material SECTION 28 CONCRETE BASES
2.Uniformly moist, but free of standing or flowing water
28-1.03C Placing
Place concrete base under section 40 -1.03F(1) except the 3rd paragraph does not apply. Spread, screed, shape, and consolidate concrete base under section 40 -1.03F(4) or under section 40 - 1.03F(5) except where there are confined work areas. If authorized for co nfined work areas, you may:
1.Spread and shape concrete base using suitable powered finishing machines and supplement with hand work as necessary.
2.Consolidate the base using high -frequency internal vibrators within 15 minutes after depositing the base on the subgrade.
3.Vibrate such that adequate consolidation occurs across the full paving width. Do not use vibrators for extensive weight shifting of the concrete base. Contraction joints must comply with section 40 -1.03B(3).
28-1.04 Payment
The payment quantity for any type of concrete base is the volume determined from the dimensions shown. The payment quantity for asphaltic emulsion (concrete base) is determined from the gauge reading on the curing seal equipment.
28-2 Lean Concrete Bases
28-2.01 General
28-2.01A Summary
Section 28 -2 includes specifications for constructing lean concrete base .
28-2.01B Definitions
Reserved
28-2.01C Submittals
28-2.01C(1) General
Submit QC test data and QC test results within 24 hours of test completion. At least 10 days before field qualification, submit:
1.Aggregate qualification test results
2.Proposed aggregate gradation
3.Mix design, including: 3.1. Proportions 3.2. Types and amounts of c hemical admixtures
4.Optional notice of intent to produce LCB qualifying for a transverse contraction joint waiver under section 28 -2.03D Submit a lean concrete base QC plan.
28-2.01C(2) Field Qualification
For each field qualification test, submit 6 of the 12 cylinders within 24 to 72 hours after preparing them. Submit field qualification data and test reports including:
1.Mixing date
2.Mixing equipment and procedures used
3.Batch volume in cubic yards, the minimum is 5 cu yd
4.Type and source of ingredients used
5.Age and strength from compression strength results SECTION 28 CONCRETE BASES The test reports must be signed by the person in responsible charge of the laboratory performing the tests.
28-2.01D Quality Assurance
28-2.01D(1) General
28-2.01D(1)(a) General
The cylinders for compressive strength testing under ASTM C31 or ASTM C192 must be 6 by 12 inches. If the aggregate gradation test results, sand equivalent test results or both comply with the contract compliance requirements but not the operating range requi rements, you may continue placing LCB for the remainder of the workday. Do not place additional LCB until you demonstrate the LCB to be placed complies with the operating range requirements.
28-2.01D(1)(b) Qualifications
Field qualification tests and calc ulations must be performed by an ACI certifie d Concrete Laboratory Technician, Grade I.
28-2.01D(1)(c) Aggregate Qualification Testing
Qualify the aggregate for each proposed aggregate source and gradation. The qualification tests include
1.a sand equiv alent and (2) an average 7 -day compressive strength under ASTM C39 of 3 cylinders manufactured under ASTM C192 except cure cylinders in molds without lids after initial curing. For the compressive strength test, the cement content for each cylinder must be 300 lb/cu yd. The 7 -day average compressive strength must be at least 610 psi. The cement must be Type II portland cement. LCB must have from 3 to 4 percent air content during aggregate qualification testing.
28-2.01D(1)(d) Field Qualification Testing
Before placing LCB, you must perform field qualification testing and obtain authorization for each mix design. Retest and obtain authorization for changes to the authorized mix designs. Notify the Engineer at least 5 business days before field qualification. Perform the field qualification at the job site or an authorized location. Field qualification testing includes tests for compressive strength, air content, and penetration or slump. For compressive strength field qualification testing:
1.Prepare 12 cyli nders under ASTM C31 except final cure cylinders in molds without lids from a single batch.
2.Perform 3 tests; each test consists of determining the average compressive strength of 2 cylinders at 7 days under ASTM C39. The average compressive strength for each test must be at least 530 psi . If you submitted a notice to produce LCB qualifying for a transverse contraction joint waiver, manufacture additional specimens and test the LCB for compressive strength at 3 days. Prepare the compressive strength cyli nders under ASTM C31 except final cure cylinders in molds without lids at the same time using the same material and procedures as the 7 -day compressive strength cylinders except do not submit 6 additional test cylinders. The average 3 -day compressive stren gth for each test must be not more than 500 psi.
28-2.01D(2) Quality Control
28-2.01D(2)(a) General
Reserved
28-2.01D(2)(b) Quality Control Manager
Reserved
28-2.01D(2)(c) Quality Control Testing
Test the LCB under the test methods and at the locations and frequencies shown in the following table: SECTION 28 CONCRETE BASES LCB Sampling Location and Testing Frequencies Quality characteristic Test method Sampling location Minimum sampling and testing frequency Sand equivalent ASTM D2419 Source 1 per 500 cubic yards but at least 1 per day of production Aggregate gradation ASTM C136 Air content ASTM C231 Job site Penetrationa ASTM C360 Slumpa ASTM C143 Compressive strength ASTM C39b aTest for either penetration or slump . bPrepare cylinders under ASTM C31 except final cure cylinders in molds without lids.
28-2.01D(3) Department Acceptance
The Department accepts LCB based on compliance with the requirements shown in the following table: LCB Requirements for Acceptance Quality characteristic Test method Requirement Compressive strength (min, psi at 7 days) ASTM C39a 530b aCylinders prepared under ASTM C31 except final cure cylinders in molds without lids. bA compressive strength test represents up to (1) 1,000 cu yd or (2) 1 day's production if less than 1,000 cu yd.
28-2.02 Materials
28-2.02A General
You may use a water -reducing chemical admixture. Water -reducing chemical admixture must comply with ASTM C494, Type A or Type F. The air content in LCB must not exceed 4 percent. If the aggregate used for LCB is produced from processed reclaimed asphalt concrete or other material that may cause the air content to exceed 4 percent, reduce the air content with an admixture. Cement content in LCB must no t exceed 300 lb/cu yd. LCB must comply with the requirements shown in the following table: LCB Requirements Quality characteristic Test method Requirement Sand equivalent (min) ASTM D2419 18 Aggregate gradation ASTM C136 Note a Air content (max, %)b ASTM C231 4 Penetration (inches) ASTM C360 0–1-1/2 nominalc Slump (inches) ASTM C143 0–3 nominalc Compressive strength (min, psi at 7 days) ASTM C39 530 Compressive strength (max, psi at 3 days)d ASTM C39 500 aComply with the table titled "Aggregate Gradation" in section 28 -2.02C. bIf no single test in the first 5 air content tests exceeds 1 -1/2 percent, no further air content tests are required. cMaximum penetration must not exceed 2 inches and maximum slump must not exceed 4 inches . dOnly applicable if you (1) submitted a notice stating intent to produce LCB qualifying for a transverse contraction joint waiver and (2) successfully field qualified the LCB for 3 -day compressive strength.
28-2.02B Cementitious Material
The SCM content requirements in the 4th paragraph of section 90 -1.02B(3) do not apply to LCB. For aggregate qualification testing, use Type II portland cement under section 90 -1.02B(2) without SCM. SECTION 28 CONCRETE BASES
28-2.02C Aggregate
Use either 1 -1/2 inch or 1 inch gradation. Do not change your selected aggregate gradation without authorization. When tested under ASTM C136, the aggregate gradation must be within the percentage passing limits for the sieve sizes shown in the following table: Aggregate Gradation Sieve size Percentage passing 1-1/2" maximum 1" maximum Operating range Contract compliance Operating range Contract compliance 2" 100 100 -- -- 1-1/2" 90–100 87–100 100 100 1" -- -- 90–100 87–100 3/4" 50–85 45–90 50–100 45–100 3/8" 40–75 35–80 40–75 35–80 No. 4 25–60 20–65 35–60 30–65 No. 30 10–30 6–34 10–30 6–34 No. 200 0–12 0–15 0–12 0–15 Aggregate must comply with the quality requirements shown in the following table: Aggregate Quality Quality characteristic Test method Operating range Contract compliance Sand equivalent (min) ASTM D2419 21 18 Compressive strength (min, psi at 7 days) ASTM C192 ASTM C39 -- 610 at 300 lb/cu yd cement content NOTE: Cement must comply with the specifications for Type II portland cement in section 90-1.02B(2).
28-2.03 Construction
28-2.03A General
Do not allow traffic or equipment on the LCB for at least 72 hours after the 1st application of the curing compound and completion of contraction joints. Limit the traffic and equipment on the LCB to that required for placing additional layers of LCB or paving.
28-2.03B Subgrade
Areas of the subgrade lower than the grade established by the Engineer must be filled with LCB.
28-2.03C Proportioning, Mixing, and Transporting
Proportion LCB under section 90-1.02F except the aggregate does not have to be separated into sizes. Mix and transport LCB under section 90 -1.02G except the 5th and 7th paragraphs in section 90 -1.02G(6) do not apply.
28-2.03D Placing
Do not mix or place LCB if the atmospheric temperature is below 35 degrees F. Do not place LCB on frozen ground. Unless otherwise described, construct LCB in minimum widths of 12 feet separated by construction joints. For LCB constructed monolithically in widths greater than 26 feet, construct a longitudinal contraction joint offset no more than 3 feet from the centerline of the width being constructed. If concrete pavement will be placed on LCB, construct longitudinal construction and longitudinal contraction joints in the LCB to provide at least 1 foot of horizontal clearance from planned longitudinal construction and longitudinal contraction joints in the concrete pavement. SECTION 28 CONCRETE BASES Construct transverse contraction joints in intervals that result in LCB areas where the lengths and widths are within 20 percent of each other. Measure the widths from any longitudinal construction or longitudinal contraction joints. The Engineer waives the requirement for transverse contraction joints if you:
1.Submitted a notice under 28 -2.01C(1)
2.Successfully field qualified LCB for 3 -day compressive strength testing under section 28 -2.02A
3.Submit QC test results for 3 -day compressive streng th under section 28 -2.01D(1)(c)
28-2.03E Finishing
For LCB to be paved with HMA, before the curing operation texture the LCB finished surface by dragging either a broom, burlap, or a spring steel tine device. If using a spring steel tine device, the device must produce a scored surface with scores parallel or transverse to the pavement centerline. Texture at a time and in a manner that produces the coarsest texture for the method used. For LCB to be paved with HMA, the finished surface must not vary more than 0.05 foot from the grade established by the Engineer. For LCB to be paved with concrete pavement, do not texture LCB. Before applying curing compound, finish LCB to a smooth surface free from mortar ridges and other projections. For LCB to be paved with concrete pavement, the finish ed surface must not be above the grade, or more than 0.05 foot below the grade established by the Engineer. The finished surface must be free from porous areas.
28-2.03F Curing
After finishing LCB, cure LCB with pigmente d curing compound under section 90 -1.03B(3) and 40 -1.03I. Apply curing compound:
1.In 2 separate applications
2.Before the atmospheric temperature falls below 40 degrees F
3.At a rate of 1 gal/150 sq ft for the first application
4.At a rate of 1 gal/20 0 sq ft for the second application Within 4 days after the first application, clean the surface and apply the second application. Immediately repair damage to the curing compound or LCB.
28-2.03G Surfaces Not Within Tolerance
For LCB not to be paved with concrete pavement, remove the base where the surface is higher than 0.05 foot above the grade established by the Engineer and replace it with LCB. For LCB to be paved with concrete pavement, remove the base wh ere the surface is higher than the grade established by the Engineer and replace it with LCB. If authorized, grind the surface with either a diamond or carborundum blade to within tolerance . After grinding LCB to be paved with concrete pavement and after a ll free water has left the surface, clean foreign material and grinding residue from the surface. Apply curing compound to the ground area at a rate of approximately 1 gal/150 sq ft. Where the surface of the LCB is lower than 0.05 foot from the grade estab lished by the Engineer, remove the base and replace it with LCB or, if authorized, fill low areas according to the pavement material as follows:
1.For HMA pavement, fill low areas with HMA that complies with the specifications for the lowest layer of pave ment. Do not fill low areas concurrently with the paving operation.
2.For concrete pavement, fill low areas with pavement concrete concurrent with the paving operation.
28-2.04 Payment
The payment quantity for lean concrete base does not include lean co ncrete base used to fill low areas of subgrade . SECTION 28 CONCRETE BASES
28-3 Rapid Strength Concrete Base
28-3.01 General
28-3.01A Summary
Section 28 -3 includes specifications for constructing rapid strength concrete base .
28-3.01B Definitions
early age: Any age less than 10 times the RSC base final set time. final set time: Elapsed time after the initial contact of the cement and water required for the mortar sieved from the concrete to reach a penetration resistance of 4,000 psi determined under ASTM C403. opening age: Age at which the RSC base achieves the specified strength for opening to traffic and construction traffic.
28-3.01C Submittals
28-3.01C(1) General
At least 10 days b efore placing RSC base, submit a mix design that includes:
1.Opening age
2.Proposed aggregate gradation
3.Proportions of hydraulic cement and aggregate
4.Types and amounts of chemical admixtures
5.Maximum time allowed between batching and placing
6.Final set time
7.Any special instructions or conditions such as water temperature requirements
28-3.01C(2) Quality Assurance Submittals
At least 45 days before placing RSC base, submit (1) a sample of cement from each proposed lot and (2) samples of prop osed admixtures in the quantities ordered. During RSC base activities, submit uniformity reports for hydraulic cement at least once every 30 days to METS, Attention: Cement Laboratory. Uniformity reports must comply with ASTM C917, except testing age and w ater content may be modified to suit the particular material.
28-3.01C(3) Quality Control Plan
Submit a rapid strength concrete base QC plan.
28-3.01D Quality Assurance
28-3.01D(1) General
28-3.01D(1)(a) General
At the preconstruction meeting be prepared to discuss the project specifications and methods of performing each item of work. Items discussed must include the processes for:
1.Production
2.Transportation
3.Placement
4.QC plan, if specified in the special provisions
5.Contingency plan
6.QC sampling and testing
7.Acceptance criteria Beams for modulus of rupture testing must be fabricated and tested under California Test 524. The beams may be fabricated using an internal vibrator under ASTM C31. For each test, 3 beam must be fabricated and the test results averaged. No single test represents more than that day's production or 130 cu yd, whichever is less. For early age testing, beams must be cured so the monitored temperatures in the beams and the test strip are always within 5 degrees F. The internal temperatures of the RSC base and early age beams SECTION 28 CONCRETE BASES must be monitored and recorded at intervals of at least 5 minutes. Thermocouples or thermistors connected to strip -chart recorders or digital data loggers must be installed to monitor the tem peratures. Temperature recording devices must be accurate to within ±2 degrees F . Until early age testing is completed, internal temperatures must be measured at 1 inch from the top, 1 inch from the bottom, and no closer than 3 inches from any edge. For ot her age testing, beams must be cured under California Test 524 except beams must be placed into sand at a time that is the earlier of either from 5 to 10 times the final set time, or 24 hours. RSC base must have an opening age modulus of rupture of not les s than 400 psi and a 7 -day modulus of rupture of not less than 600 psi.
28-3.01D(1)(b) Preconstruction Meeting
Reserved
28-3.01D(1)(c) Test Strip
Reserved
28-3.01D(2) Quality Control
28-3.01D(2)(a) General
Reserved
28-3.01D(2)(b) Quality Control Manag er
Reserved
28-3.01D(2)(c) Quality Control Testing
Test the rapid strength concrete base under the test methods and at the locations and frequencies shown in the following table: Rapid Strength Concrete Base Sampling Location and Testing Frequencies Quality characteristic Test method Sample Location Minimum testing frequencya Cleanness value California Test 227 Source 1 per 500 cubic yards but at least 1 per shift Sand equivalent California Test 217 Aggregate gradation California Test 202 Air content California Test 504 1 per 130 cu yd but at least 1 per shift Yield California Test 518 1 per shift Slump or penetration ASTM C143 or California Test 533 1 per 2 hours of placement Density California Test 518 Job site 1 per shift Aggregate moisture meter calibrationb California Test 223 or California Test 226 1 per shift Modulus of rupture California Test 524 1 per 130 cu yd but at least 1 per shift aTest at the most frequent interval. bCheck calibration of the plant moisture meter by comparing moisture meter readings with California Test 223 or California Test 226 test results. Notify the Engineer at least 2 business days before any sampling and testing. Submit testing results within 15 minutes of testing completion. Record inspection, sampling, and testing on the forms accepted with the QC plan and submit them within 48 hours of completion of each day of production and within 24 hours of 7 -day modulus of rupture tests. During t he placement of RSC base, fabricate beams and test for the modulus of rupture:
1.At opening age
2.At 7 days after placing the first 30 cu yd
3.At least once every 130 cu yd SECTION 28 CONCRETE BASES
4.Within the final truckload Opening age tests must be performed in the presen ce of the Engineer.
28-3.01D(3) Department Acceptance
The Department accepts RSC base based on compliance with the requirements shown in the following table: RSC Base Requirements for Acceptance Quality characteristic Test method Requirement Modulus of rupture (min, psi at 7 days) California Test 524 600 The Engineer adjust payment for RSC base for the 7 -day modulus of rupture as follows:
1.Payment for a base with a modulus of rupture of 600 psi or greater is not adjusted.
2.Payment for a base with a modulus of rupture of less than 600 and greater than or equal to 550 psi is reduced by 5 percent.
3.Payment for a base with a modulus of rupture of less than 550 and greater than or equal to 500 psi is reduced by 10 percent.
4.Payment for a base with a modulus of rupture of less than 500 psi is not adjusted and no payment is made. Remove and replace this base.
28-3.02 Materials
28-3.02A General
Reserved
28-3.02B Rapid Strength Concrete Base
Concrete for RSC base must be RSC. For batches with a volume of 1 cu yd or more, comply with one of the following methods:
1.Batch the ingredients at a central batch plant and charge them into a mixer truck for transportation to the pour site.
2.Batch the ingredients except the cement at a ce ntral batch plant and charge them into a mixer truck for transportation to a cement silo and weigh system, which must proportion cement for charging into the mixer truck.
3.Batch ingredients except the cement at a central batch plant and charge them into a mixer truck for transportation to a location where preweighed containerized cement is added to the mixer truck. The cement preweighing operation must use a platform scale. The platform scale must have a maximum capacity of 2.75 tons with a maximum gradua tion size of 1 lb. Preweigh cement into a fabric container. The minimum amount of cement to be proportioned into any single container must be 1/2 of the total amount required for the load of RSC base being produced.
4.Proportion cement, water, and aggrega te volumetrically. For the combined aggregate gradation, the difference between the percent passing the 3/8 -inch sieve and the percent passing the no. 8 sieve must be at least 16 percent of the total aggregate. You may use Type C accelerating and Type E a ccelerating and water reducing chemical admixtures.
28-3.02C Curing Seal
Asphaltic emulsion must be Grade SS -1.
28-3.03 Construction
28-3.03A General
Reserved
28-3.03B Subgrade
Reserved SECTION 28 CONCRETE BASES
28-3.03C Placing, Spreading, and Shaping
You may place RSC base in 2-lane monolithic segments. A longitudinal joint is not required in the center of the concrete base. Construct transverse contraction joints at 30 -foot intervals. Cut a groove in the RSCB with a power -driven concrete saw. Grooves for longitudinal and transverse contraction joints must be the minimum width possible for the type of saw used. Immediately wash slurry from the joint with water at a pressure less than 100 psi. The RSC ba se finished surface must not vary more than 1/4 inch from the bottom of a 12 -foot-long straightedge placed parallel with the center line. Broom the RSC base surface to produce a uniform, rough surface. Do not broom the surface until the concrete base has s et sufficiently.
28-3.03D Curing
Begin curing work as soon as free water leaves the RSC base surface. Cure RSC base by applying a curing seal of asphaltic emulsion under section 94. Apply curing seal at a rate f rom 0.15 to 0.25 gal/sq yd. The Engineer determines the exact application rate. If you damage applied curing seal, immediately cover the damaged area with additional curing seal. Do not remove curing seal until surfacing is placed. If you do not place HMA within 24 hours of applying curing seal, apply more asphaltic emulsion at a rate from 0.03 to 0.05 gal/sq yd residual binder content immediately before placing HMA.
28-3.03E Surfaces Not Within Tolerance
RSC base must be within 0.05 foot of the grade established be the Engineer. Remove and replace hardened RSC base with a surface higher than 0.05 -foot above the grade established by the Engineer with RSC base, or if authorized, hi gh areas may be ground until the surface of RSC base conforms to the tolerances specified. Grinding equipment must be equipped with diamond or carborundum blades. Clean the ground area of RSC base that is to be covered with pavement of all foreign material and grinding residue as soon as any free water has left the surface and apply curing seal. Where the surface of RSC base is lower than 0.05 foot from the grade established by the Engineer, remove the base and replace it with RSC base or, if authorized, fi ll low areas with HMA that complies with the specifications for the lowest layer of pavement. Do not fill low areas concurrently with the paving operation.
28-3.04 Payment
Not Used
28-4 Lean Concrete Base Rapid Setting
28-4.01 General
28-4.01A Summary
Section 28 -4 includes specifications for constructing lean concrete base rapid setting .
28-4.01B Definitions
early age: Any age less than 10 times the lean concrete base r apid setting final set time. final set time: Elapsed time after initial contact of cement and water required for the mortar sieved from the concrete to reach a penetration resistance of 4,000 psi determined under ASTM C403. opening age: Age at which the le an concrete base rapid setting achieves the specified strength for opening to traffic, including construction traffic.
28-4.01C Submittals
28-4.01C(1) General
At least 25 days before field qualification, submit the name of your proposed testing laborator y. Submit QC test date and QC test results within 24 hours of test completion. SECTION 28 CONCRETE BASES Submit a lean concrete base rapid setting QC plan.
28-4.01C(2) Mix Design
At least 10 days before field qualification, submit a mix design for lean concrete base rapid setting and include:
1.Opening age
2.Proposed aggregate gradation
3.Mix design, including 3.1. Proportions 3.2. Types and amounts of chemical admixtures
4.Maximum time allowed between batching and placing
5.Range of ambient temperatures over which the mix design is applicable
6.Final -set-time
7.Aggregate qualification test results if required Submit 1 mix design for each ambient temperature variation anticipated during base placement. Each mix design must have a maximum ambient temperature range of 18 de grees F. Submit compressive strength development data for each mix design. You may use strength development data from laboratory -prepared samples. The testing ages for strength development data must include 1 hour before opening age, opening age, 1 hour af ter opening age, 24 hours, and 7 days.
28-4.01C(3) Field Qualification
Submit field qualification data and test reports including:
1.Mixing date
2.Mixing equipment and procedures used
3.Batch volume in cubic yards, minimum 5 cu yd
4.Type and source of ingredients used
5.Age and strength at time of cylinder testing Reports must be certified with a signature by an official in responsible charge of the laboratory performing the tests.
28-4.01D Quality Assurance
28-4.01D(1) General
28-4.01D(1)(a) Gene ral
For compressive strength testing, prepare 6 cylinders under California Test 540. Test cylinders must be 6 by 12 inches. As an alternative to rodding, a vibrator may be used under California Test 524. Test cylinders under California Test 521 and perform 3 tests with each test consisting of 2 cylinders. The test result is the average from the 2 cylinders.
28-4.01D(1)(b) Field Qualification
Before placing lean concrete base rapid setting, you must perform field qualification testing and obtain authorizati on for each mix design. Retest and obtain authorization for changes to authorized mixed designs. Proposed mix designs must be field qualified before you place the base represented by those mix designs. The technician performing the field test must hold cur rent ACI certification as a Concrete Field Testing Technician -Grade I. Notify the Engineer at least 5 days before field qualification. Perform field qualification within the job site or a location authorized. Field qualification testing includes compressiv e strength, air content, and penetration or slump in compliance with the table titled "L CB Rapid Setting Requirements." Field qualification must comply with the following:
1.Test for compressive strength at opening age and 7 days of age . SECTION 28 CONCRETE BASES
2.At opening age, the compressive strength for each test must be at least 180 psi and the average strength for the 3 tests must be at least 200 psi .
3.At 7 days age, the compressive strength for each test must be at least 600 psi and the average strength for t he 3 tests must be at least 725 psi .
28-4.01D(2) Quality Control
28-4.01D(2)(a) General
Reserved
28-4.01D(2)(b) Quality Control Manager
Reserved
28-4.01D(2)(c) Quality Control Testing
Test the base under the test methods and at the locations and frequ encies shown in the following table: LCB Rapid Setting Sampling Location and Testing Frequencies Quality characteristic Test method Sampling location Minimum sampling and testing frequency Sand equivalent ASTM D2419 Source 1 per 500 cu yd, minimum 1 per day of production Aggregate gradation ASTM C136 Air content ASTM C231 Job site 1 per 4 hours of placement work, plus one in the last hour of placement work Penetrationa ASTM C360 Slumpa ASTM C143 Compressive strength California Test 521 aTest either penetration or slump . During placement of lean concrete base rapid setting, fabricate cylinders and test compressive strength for opening age and 7 days. Opening age tests must be performed in the presence of the Engineer.
28-4.01D(3) Depar tment Acceptance
The Department accepts LCB rapid setting based on compliance with the requirement shown in the following table: LCB Rapid Setting Requirements for Acceptance Quality characteristic Test method Requirement Compressive strength (min, psi at 7 days) California Test 521a 725 aCylinders made under California Test 540 .
28-4.02 Materials
28-4.02A General
LCB rapid setting must comply with the requirements shown in the following table: SECTION 28 CONCRETE BASES LCB Rapid Setting Requirements Quality characteristic Test method Requirement Sand equivalent (min) ASTM D2419 71a Aggregate gradation ASTM C136 Comply with section 28 - 2.02C Air content (max, %)b ASTM C231 4 Penetration (inches) ASTM C360 0–2-1/2 nominal 3 maximum Slump (inches) ASTM C143 0–5 nominal 6 maximum Compressive strength (min, psi at 7 days) California Test 521 725 Compressive strength (min, psi at opening age) California Test 521 200 aIf aggregate is qualified under section 28 -4.02D, item 2, the minimum is 18. bIf no single test in the first 5 air content tests exceeds 1 -1/2 percent, no further air content tests are required.
28-4.02B Cement
Cement must comply with the requirements for RSC.
28-4.02C Chemical Admixtures
Chemical admixtures must comply with chemical admixtures for concrete except you may use Type E chemical admixture. You may submit a request to use citric acid or borax. Your request must include a request from the cement manufacturer and a test sample.
28-4.02D Aggregates
Aggregate must com ply with either of the following:
1.Section 90 -1.02C except aggregate gradation must comply with the aggregate gradation table in section 28 -2.02C .
2.Section 28 -2.02C and the following: 2.1. Qualify the aggregate for each proposed aggregate source and gr adation . 2.2. Qualification tests include (1) sand equivalent and (2) average 7 -day compressive strength under ASTM C39 on 3 specimens manufactured under ASTM C192. The cement content for this test must be 300 lb/cu yd, and the 7 -day compressive strength must be at least 610 psi. Cement must be Type II portland cement under section 90 -1.02B(2) without SCM.
28-4.03 Construction
28-4.03A General
Construct LCB rapid setting under section 28 -2.03 except (1) section 28 -2.03A does not apply and (2) t he 3rd through 5th paragraphs of section 28 -2.03D do not apply. Concrete paving operations with equipment not supported by the base may start before opening age. Do not open pavement for traffic before opening age of the LCB rapid setting. Any other paving operations must start after the final set time of the base. The base must have a compressive strength of at least 450 psi under California Test 521 before:
1.Placing HMA
2.Placing other base material
3.Operating equipment on the base
28-4.03B Proportioning, Mixing, and Transporting
For batches 1 cu yd or more, comply with one of the following methods:
1.Batch the ingredients at a central batch plant and charge the m into a mixer truck for transportation to the pour site. SECTION 28 CONCRETE BASES
2.Batch the ingredients except the cement at a central batch plant and charge them into a mixer truck for transportation to a cement silo and weigh system, which must proportion cement for charging into the mixer truck.
3.Batch ingredients except the cement at a central batch plant and charge them into a mixer truck for transportation to a location where preweighed containerized cement is added to the mixer truck. The cement preweighing operation m ust utilize a platform scale. The platform scale must have a maximum capacity of 2.75 tons with a maximum graduation size of 1 lb. Preweigh cement into a fabric container. The minimum amount of cement to be proportioned into any single container must be 1/ 2 of the total amount required for the load of lean concrete base rapid setting being produced.
4.Proportion cement, water, and aggregate volumetrically under ASTM C685 or section 90 -3.02B .
28-4.03C Spreading, Compacting and Shaping
You may use metal or wood side forms. Wood side forms must be at least 1 -1/2 inches thick. After you deposit the LCB rapid setting on the subgrade, consolidate it with high -frequency internal vibrator s. Consolidate adjacent to the forms and across the full pavement width. Place the base as nearly as possible to its final position. Spread and shape the base with powered finishing machines and supplement with hand work if necessary . After you place lean concrete base rapid setting, do not add water to the surface to facilitate finishing. If authorized, you may use surface finishing additives as recommended by the manufacturer of the cement.
28-4.04 Payment
If volumetric proportioning is used and calibrat ion is performed more than 100 miles from the project limits, the Department deducts $1,000 for each calibration session.
28-5 Concrete Base
28-5.01 General
28-5.01A Summary
28-5.01B Definitions
Reserved
28-5.01C Submittals
Submit a concrete base QC plan.
28-5.01D Quality Assurance
28-5.01D(1) General
For each lot of concrete for a concrete base:
1.Quantity must not exceed 1,000 cu yd
2.Department determines the modulus of rupture of test beams aged 28 days under California Test 523
3.Department calculates the modulus of rupture by averaging the individual test results of 2 beams aged for 28 days
28-5.01D(2) Quality Control
28-5.01D(2)(a) General
Reserved
28-5.01D(2)(b) Quality Control Manager
Reserved
28-5.01D(2)(c) Quality Control Testing
Test the concrete base under the test methods and at the locations and frequencies shown in the following table: SECTION 28 CONCRETE BASES Concrete Base Sampling Locati on and Testing Frequencies Quality characteristic Test method Sample location Minimum testing frequencya Cleanness value California Test 227 Source 1 per 500 cubic yards but at least 1 per shift Sand equivalent California Test 217 Aggregate gradation California Test 202 Air content California Test 504 1 per 500 cu yd but at least 1 per shift Yield California Test 518 1 per shift Slump or penetration ASTM C143 or California Test 533 1 per 2 hours of placement Density California Test 518 Job site 1 per shift Aggregate moisture meter calibrationb California Test 223 or California Test 226 1 per shift Modulus of rupture California Test 524 1 per 500 cu yd but at least 1 per shift aTest at the most frequent interval. bCheck calibration of the plant moisture meter by comparing moisture meter readings with California Test 223 or California Test 226 test results.
28-5.01D(3) Department Acceptance
The Department accepts a concrete base based on compliance with the requirements shown in the following table: Concrete Base Requirements for Acceptance Quality characteristic Test method Requirement Modulus of rupture (min, psi at 28 days) California Test 523 570 Acceptance for the modulus of rupture is on a lot basis. The Department provides the molds and machines for the modulus of rupture acceptance testing. Provide any material and labor the Engineer may require for the testing.
28-5.02 Materials
28-5.02A General
Reserved
28-5.02B Portland Cement Concrete
Concrete must be PCC. For the combined aggregate gradation, the difference between the percentage passing the 3/8 -inch sieve and the percentage passing the no. 8 sieve must be at least 16 percent of the total aggregate. The specifications for the reduction in operating range and contract compliance for cleanness value and sand equivalent for coarse aggregate in section 90 -1.02C(2), and fine aggregate in section 90 -1.02C(3) do not apply to a concrete base. The base must contain not less than 550 lb of cementi tious material per cubic yard.
28-5.02C Curing Seal
The curing seal must be asphaltic emulsion Grade SS -1.
28-5.03 Construction
28-5.03A General
Aggregate and bulk cementitious material must be proportioned by weight using authorized automatic proportio ning devices. SECTION 28 CONCRETE BASES
28-5.03B Placing, Spreading, and Shaping
You may place concrete base in 2-lane monolithic segments. A longitudinal joint is not required in the center of the base. The finished surface must not vary more than 1/4 inch from the bottom of a 12 -foot-long straightedge placed parallel with the centerline. After the base has suf ficiently set, broom the concrete base surface to produce a uniform, rough surface. After the free water leaves the surface and the surface is finished but not later than 3 hours after placement, cure the base by applying asphaltic emulsion. Apply the curi ng seal at a rate from 0.15 to 0.25 gal/sq yd. The Engineer determines the exact application rate. If you damage the applied curing seal, immediately cover the damaged area with additional curing seal. Construct transverse contraction joints at 30 -foot int ervals. Apply the curing seal on cleaned contraction joints. Saw transverse contraction joints before any volunteer cracking occurs and after the concrete base is hard enough to saw without spalling, raveling, or tearing. The base must be within 0.05 foot of the grade established be the Engineer . Where the surface of the base is lower than 0.05 foot from the grade established by the Engineer, remove and replace it with concrete base or, if authorized, fill low areas with HMA that complies with the specifica tions for the lowest layer of pavement. Do not fill low areas concurrently with the paving operation. If you do not place the HMA within 24 hours of applying curing seal, apply more asphaltic emulsion at a residual binder rate from 0.03 to 0.05 gal/sq yd i mmediately before placing the HMA.
28-5.04 Payment
Not Used
28-6 28-14 Reserved
28-15 Existing Concrete Bases
28-15.01 General
28-15.01A General
Section 28-15.01 include s general specifications for performing work on existing concrete bases .
28-15.01B Materials
Not Used
28-15.01C Construction
Not Used
28-15.01D Payment
Not Used
28-15.02 Replace Bases
Reserved
28-15.03 28-15.08 Reserved
Source: California Standard Specifications, 2024 Edition. Pages 421–436 of 1,372.