tolerances- section 346-6 - ctqp home page lab technician spec course... · tolerances- section...

Student Manual Concrete Laboratory Technician

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Do not add water to delivered concrete when it is within the target Range for slump

Tolerances- Section 346-6.4

346-6.4 Tolerances: Meet the following tolerances from target values for plastic concrete properties specified in 346-3.1.


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Tolerance Slump Range

1-1/2” Dry 1-1/2” Wet

Accept- WaterMust NOTbe added

Accept- WaterMust NOTbe added

Reject Reject

¾” Dry ¾” WetTargetSlump

Target Slump Range

Accept- NotifyPlant to Adjust &May add water

At site

Accept- NotifyPlant to Adjust

346-6.4 Tolerances Reject concrete with slump exceeding the above tolerances or air content exceeding the ranges in Table 2. Do not allow concrete to remain in a transporting vehicle to reduce slump. Water may be added in accordance with the approved QCP.


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12”

Target Slump3”

0.75”0.75” Target 1.5”

1.5”

Tolerance

No water to be addedwhen in “Target”

ToleranceTarget

NON-DRILLED SHAFT CONCRETEWITHOUT HRWR


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DRILLED SHAFT CONCRETE

12”

Target Slump8”

1.0”

1.0” 1.0”

1.0”

Target Tolerance

ToleranceTarget

No water to be addedwhen in “Target”


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• No mixing of concrete when the ambient temperature is below 45oF and falling.

• May mix when ambient temperature in shade is above 40oF and rising.

• Heating aggregates or using salt to reduce freezingtemperatures is not allowed.

• Unless being heat cured, protect concrete from freezing until it reaches a minimum compressive strength of 1500 psi

Cold Weather Concreting-Section 346-7.4

346-7.4 Concreting in Cold Weather: Do not mix concrete when the air temperature is below 45ºF [7ºC] and falling. The Contractor may mix and place concrete when the air temperature in the shade, and away from artificial heat, is 40ºF [4ºC] and rising. Protect the fresh concrete from freezing until the concrete reaches a minimum compressive strength of 1,500 psi [10 MPa] unless the concrete is to be heat cured.


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• “Hot Weather” conditions occur when the concrete temperature is between 85oF and 100oF

• Concrete temperature is not to exceed 100oF

• Hot Weather measures may be implemented for concrete temperatures between 85oF and 100oF

Hot Weather Concreting-Section 346-7.5

The most favorable temperature for freshly mixed concrete is lower during hot weather than can usually be obtained without artificial cooling. A concrete temperature of 50°F to 60°F is desirable but not always practical. For most work, it is impractical to limit the maximum temperature of concrete as placed because circumstances vary widely. A limit that would serve successfully at one jobsite could be highly restrictive at another.

346-7.5 Concreting in Hot Weather: Hot weather concreting is defined as the production, placing and curing of concrete when the concrete temperature at placing exceeds 85ºF [30ºC] but is less than 100ºF [40ºC].

Unless the specified hot weather concreting measures are in effect, reject concrete exceeding 85ºF [30ºC] at the time of placement. Regardless of special measures taken, reject concrete exceeding 100ºF [40ºC]. Predict the concrete temperatures at placement time and implement hot weather measures to avoid production shutdown.


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HOT WEATHER FACTS

• Hot weather presents:- increased water demand- accelerated slump loss- A quicker rate of setup- increased tendency for plastic cracking- difficulty controlling entrained air- need for prompt early curing

• Adding water at site to cool mix can:- decrease strength- decrease durability and watertightness- nonuniform surface appearance- increased tendency for drying shrinkage

Hot Weather Concreting

As concrete temperature increases, there is a loss in slump that is often compensated for by adding more water at the jobsite, which can have adverse effects. At higher temperatures, a greater amount of water is required to hold slump constant than is needed at lower temperatures. Adding water without adding cement results in a higher water-cement ratio, thereby lowering the strength at all ages.


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• Cool the aggregates- Shaded from sun- Sprinkling

• Cool the water- bury the supply line- shade the line- insulate the line- use ice

Hot Weather Concreting

The usual method of cooling concrete is to lower the temperature of the concrete materials before mixing. One or more of the ingredients should be cooled. In hot weather, the aggregates and water should be kept as cool as practicable, as these materials have a greater influence on temperature after mixing than other components. Of the materials in concrete, water is the easiest to cool. Mixing water from a cool source should be used and tanks and pipelines carrying the mixing water buried, insulated, shaded, etc.

Ice can be used as part of the mixing water provided it is completely melted by the time mixing is completed. When using crushed ice, care must be taken to store it at a temperature that will prevent the formation of lumps. Aggregates have a pronounced effect on the fresh concrete temperature because they represent 70% to 85% of the total weight of concrete. Stockpiles should be shaded from the sun an kept moist by sprinkling. Since evaporation is a cooling process, sprinkling provided effective cooling, especially when the relative humidity is low. Sprinkling of coarse aggregates should be adjusted to avoid producing excessive variations in the free moisture content and thereby causing a loss of slump uniformity.


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• Perform the plastic property tests on the initial delivery of each concrete design mix each day

• The QC technician shall be present throughout the entire placement.

• Multiple placement sites requires min. 2 technicians

Plastic Concrete Testing-Section 346-8

346-8 Plastic Concrete Sampling and Testing.

….Perform plastic concrete tests on the initial delivery of each concrete design mix each day. Ensure QC technicians meeting the requirements of Section 105 are present and performing tests throughout the placement operation. Ensure one technician is present and performing tests throughout the placement operation at each placement site. If a placement site has multiple concrete trucks, identify the number of technicians in the Quality Control Plan. If a placement site has multiple trucks placing concrete, then have at least two technicians present at that site.

Photograph of Technician checking air in concrete.


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• Placement operations will not proceed until the delivered concrete complies with plastic properties tolerances .

• Non-complying loads which cannot be adjusted at the jobsite are to be rejected.

• A failing QC test will result in the rejection of the remainder of the load and termination of the LOT.

• Make cylinders representing the failing LOT from the same sample of concrete.

Plastic Concrete Testing-Section 346-8

346-8 Plastic Concrete Sampling and Testing. Continued….Do not proceed with the placement operation until the delivered concrete complies with plastic properties specified. After placement begins, perform QC tests to ensure compliance with Specification requirements on each LOT of concrete. Reject non-complying loads which cannot be adjusted at the jobsite. Ensure that corrections are made on subsequent loads.

Furnish sufficient concrete of each design mix as required by the Engineer for verification testing…. ….If a QC test fails, reject the remainder of that load, terminate the LOT, and notify the Engineer. Make cylinders representing that LOT from the same sample of concrete.

Following termination of a LOT, re-initiate initial plastic properties tests until such time as the water to cementitious materials ratio, air content, temperature and slump comply with the Specification requirements. Initiate a new LOT once the testing indicates compliance with Specification requirements.


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Calculating the Water/Cementitious Ratio

1. Determine the amount of free water on the coarse & fine aggregate.

2. Divide the coarse aggregate total weight by the free water percent plus 1.00, which gives the saturated surface dry (SSD) weight of the aggregate.

3. Subtract the SSD weight from the Total aggregate weight you started with. This provides the weight of free water on the aggregate. Repeat for fine aggregate. Take free water calculations to 4 places past decimal and round to 3 places.

4. Calculate batch water. Multiply the gallons of batch water by 8.33. Also do the same for any water added at the jobsite. Take 4 places past the decimal and round to 3 places.

5. Add together free water on aggregates, pounds of batch and jobsite added water. This gives total pounds of water contained in concrete.

6. Divide the total water in pounds by the cementitious material (cement or cement & pozzolan). This is the WATER/CEMENTITIOUS RATIO. Take 3 places past the decimal and round back 2 places.

Water/Cementitious Ratio

These are the steps in performing the Water Cementitious Material Ratio Calculation.


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MIX INFORMATION

Coarse Aggregate 1,722.0000 lbs. 1% free water

Fine Aggregate 1,172.0000 lbs. 6% free water

Batch Water 21.0000 gallons

Added Water 0.0000 gallons

Fly Ash (Pozzolan) 125.0000 lbs.

Cement 533.0000 lbs.


SAMPLE PROBLEM(All weights are for 1.0 cubic yard)

A w/c calculation sheet can be found in the rear of FM 5-501 in Tab 8.


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STEP 1 – Coarse Aggregate

TOTAL WEIGHT: FREE WATER + 1.00:1,722.0000 lbs. 1.01%



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STEP 2 – Fine Aggregate

TOTAL WEIGHT: FREE WATER + 1.00:1,172.0000 lbs. 1.06%



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STEP 3 - Batch Water

STEP 4 – Added Water

STEP 5 – Total Water



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STEP 6 – Cement

STEP 7 – Fly Ash

STEP 8 – Total Cementitious Material

STEP 9 – Water/Cementitious Ratio



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346-9.3 Strength Test Definition

• Average compressive strength of 3 cylinders, per LOT

346-9.4 Acceptance of Hardened Concrete

• For acceptance, LOT strength tests must equal or exceed the specified minimum strength

Acceptance Testing- Section 346-9

346-9.3 Strength Test Definition: The strength test of a LOT is defined as the average of the compressive strengths tests of three cylinders cast from the same sample of concrete from the LOT. 346-9.4 Acceptance of Hardened Concrete: Hardened Concrete will be accepted or rejected on the basis of strength test results as defined by 346-9.3. Do not discard a cylinder strength test result based on low strength (strength below the specified minimum strength as per the provisions of 346-3 and 346-9). When QC strength test results are verified, the Engineer will accept the concrete based on QC test results. The Engineer will accept at full pay only LOTS of concrete represented by strength test results which equal or exceed the respective specified minimum strength.


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• Department averages the QC and Verification compressive strength test data and determines Comparison Criteria

• QC verified when comparison difference same or less than Criteria

• Resolution required when comparison more than Criteria

• QC and Verification hold cylinder transported, by each to the resolution testing laboratory within 72 hours


346-9 Acceptance Sampling and Testing.

….The Department will average the QC and Verification compressivestrength test data and based on this average at 28 days determine the Comparison Criteria as shown in Table 8. When the difference between QC and Verification are less than or equal to the Comparison Criteria, the QC data is verified. When the difference between QC and verification data exceeds the Comparison Criteria the Engineer will initiate the resolution procedure in accordance with 346-9.5. The QC and Verification laboratories will transport their own hold cylinder to the resolution testing laboratory within 72 hours after the Engineer notifies the Contractor that a resolution is required.


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Comparison Criteria Table

• QC verified if QC and VT difference are equal to or lessthan Comparison Criteria

• Resolution initiated when QC and VT differences are greater than Comparison Criteria


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When a concrete acceptance strength test result falls more than 10% or 500 psi (3.5 MPa) below the specified minimum strength.

Core strength results in lieu of cylinder strengths and are final

• Cause for an investigation

EitherStructural Analysis

orCoring

Low Strength Concrete - Section 346-10

346-10 Investigation of Low Strength Concrete for Structural Adequacy.346-10.1 General: When a concrete acceptance strength test result falls more than 10% or 500 psi [3.5 MPa] below the specified minimum strength, whichever is the greater deviation from the specified minimum strength, and the Department determines that an investigation is necessary, make an investigation into the structural adequacy of the LOT of concrete represented by that acceptance strength test result at no additional expense to the Department. The Engineer may also require the Contractor to perform additional strength testing as necessary to determine structural adequacy of the concrete.

Furnish either a structural analysis performed by a Specialty Engineer to establish strength adequacy or drilled core samples as specified in 346-10.3 to determine the in-place strength of the LOT of concrete in question at no additional expense to the Department. Obtain the Engineers approval before taking any core samples. When the concrete is deemed to have low strength, obtain and test the cores and report the data to the Engineer within 14 days of the 28 day compressive strength tests. Core strength test results obtained from the structure will be accepted by both the Contractor and the Department as the in-place strength of the LOT of concrete in question. The core strength test results will be final and used in lieu of the cylinder strength test results for determination of structural adequacy and any pay adjustment. The Department will calculate the strength value to be the average of the compressive strengths of the three individual cores. This will be accepted as the actual measured value.


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• Obtain drilled core samples, minimum of 3

• Locate cores near location of test cylinders

• Engineer tests cores within 3 days of being obtained

Then:If Core Test Results Are:Consider the concrete structurally adequate

Less than 10% below or no greaterthan 500 psi (3.5 MPa) from the specified minimum strength More than 10% or greaterthan 500 psi (3.5 MPa) below the specified minimum strength

Consider the concrete structurally questionable

Low Strength Concrete - Section 346-10

346-10.2 Determination of Structural Adequacy: If core strength test results are less than 500 psi [3.5 MPa] or 10%, whichever is greater, below the specified minimum strength, consider the concrete represented by the cores structurally adequate. If the core strength test results are more than 10% or 500 psi [3.5 MPa], whichever is greater, below the specified minimum strength, the Department will consider the concrete represented by the cores structurally questionable. Submit a structural analysis performed by a Specialty Engineer. If the results of the structural analysis, approved by the Department, indicates adequate strength to serve its intended purpose with adequate durability, the Contractor may leave the concrete in place subject to the requirements of 346-11, otherwise, remove and replace the LOT of concrete in question at no additional expense to the Department.

346-10.3 Coring for Determination of Structural Adequacy: Furnish three undamaged core samples taken from the same approximate location as where the structural questionable concrete represented by the low strength concrete test cylinders was placed. Select the location of the drilled cores so that the structure is not impaired and does not sustain permanent damage after repairing the core holes. Obtain the approval of the Engineer to core, and of the core location prior to drilling.

346-10.4 Core Conditioning and Testing: The Department will test the cores in accordance with ASTM C 42 [ASTM C 42M]. The Engineer will make the determination whether to test the cores in a dry or wet condition. If the Engineer decides to test the cores in a wet condition, immerse the cores in water for at least 40 hours, and test the cores wet. The cores will be tested within 3-days after obtaining the samples.


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• Accordance with ASTM C 31

• Curing of concrete cylinders and beams

- initial curing- final curing- field curing

• Laboratory meeting qualifications of SSRBC 6.9

• QC provides initial curing for all QC, VT &IV samples

Curing of Concrete Samples

It is imperative that concrete samples obtained not only be obtained properly, but cured properly. Improper curing can impact the validity of the compression test results.

QC must provide facilities capable of holding all QC, VT and IV concrete samples for Initial Curing. QC then transports their samples to an approved final curing facility and the Department transports theirs.

Field curing, not generally used for acceptance testing, is generally a performance related curing (i.e. form removal).

346-9 Acceptance Sampling and Testing.

346-9.1 General:

…. Provide curing facilities for initial curing that have the capacity to hold all QC, Verification, and Independent Verification cylinders simultaneously. All cylinders will be clearly identified. Deliver the QC samples to the final curing facility in accordance with ASTM C 31 [ASTM C 31M]. At this same time, the Department will deliver the verification samples to their final curing facility.

Test the QC samples for compressive strength at the age of 28 days in a laboratory meeting and maintaining at all times the qualification requirements listed in 6-9.


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Initial Curing (in molds)

• The proper storage of the concrete samples for up to48 hours after casting

• Temperature ranges 60o to 80o

- Strengths of >6,000 psi at 68o to 78o

• Prevent loss of moisture from samples

• Vibration-free environment


Initial Curing is the curing process immediately after the casting of the samples.

ASTM C-31M details the proper methods and processes to be used and you should be familiar with this ASTM Standard.


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Final Curing (molds removed)

• The proper storage of the concrete samples within30 minutes of mold removal

• Temperature ranges 73 ±3o

• Minimum final curing time before testing beams is 20 hrs.

• Soak tank or moist room


Final Curing is the curing process used for storage until testing of the sample.

ASTM C-31M details the proper methods and processes to be used and you should be familiar with this ASTM Standard.


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Laboratory Requirements

• Must be qualified and have current Department approval:

a. Current AASHTO (AAP) accreditation.b. Inspected on a regular basis per … ASTM C 1077 c. Construction Materials Engineering Council (CMEC)

• It is prohibited as a conflict of interest for a non-Department laboratory to perform Contractor Quality Control testing and other Acceptance Program testing on the same Contract.

6-9 Laboratory Qualification Program.Testing Laboratories participating in the Department’s Acceptance Program

must be qualified under one of the following and have current Department approval during testing of Department products:a. Current AASHTO (AAP) accreditation.b. Inspected on a regular basis per … ASTM C 1077 for concrete for test methods used in the Acceptance Program, with all deficiencies corrected, and under the supervision of a Specialty Engineer.c. Construction Materials Engineering Council (CMEC) program and other independent inspection programs acceptable to the Engineer and equivalent to a or b above.

Obtain Department approval prior to beginning testing….…Meet and maintain the qualification requirements at all times. Testing without the Department’s priorapproval may result in rejection of the test results. Continued Department approval will be subject tosatisfactory results from periodic evaluations, including Independent Assurance program. In case of disapproval, resolve the issues to the Department’s satisfaction and obtain approval prior to further testing.

It is prohibited as a conflict of interest for a non-Department laboratory to perform Contractor Quality Control testing and other Acceptance Program testing on the same Contract.


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SECTION 346PORTLAND

CEMENTCONCRETE

Any Questions


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Section 9.2

MATERIALS MANUAL

SECTION 9.2CONCRETE

PRODUCTIONFACILITIES

GUIDELINES

MATERIALS MATERIALS MANUALMANUAL

SECTION 9.2SECTION 9.2CONCRETE CONCRETE

PRODUCTIONPRODUCTIONFACILITIES FACILITIES

GUIDELINESGUIDELINES


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9.2.4 Materials Requirements

• Acceptance is based upon certified mill analysis and Delivery Ticket

9.2.4.2 Cementitious Materials

9.2.4.7 Batch Adjustments For Materials

• Permissible adjustment to previously approved design mix is ± 6.5% per cubic yard [cubic meter] but not less than the specified minimum

9.2.4.2 Cementitious Material

Acceptance at the plant shall be based upon certified mill analysis. As a check on current quality, samples may be obtained and tested by the Producer or the Department.

Measure the cementitious materials by mass within an accuracy of 1% of the required total amount, except that for concrete batches of 3 yd3 [3 m3] or less, accuracy of 2% is allowed. Weigh the cementitious materials separately from other materials. When weighing cementitious materials in a cumulative weigh hopper, weigh the cement first. Measure silica fume slurry as an admixture.


Permissible adjustments to previously approved design mixes that may be made without a new design mix request are as follows:

(3) Cementitious Materials: ±6.5% per cubic yard [cubic meter], but not less than the specified minimum for that class of concrete.


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9.2.4.3 Aggregates• All aggregates shall be from Department approved

sources

9.2.4.3.1 Wetting Coarse Aggregate Stockpiles, Storage Bins And Silos

• Coarse aggregate shall be sprinkled with water for 24 hours before introduction into the concrete

9.2.4.7 Batch Adjustments For Materials• Permissible adjustment for all aggregates to previously

approved design mix is ± 75 lbs/yd3 [45 kg/m3]


9.2.4.3 Aggregates

All Aggregate shall be obtained from Department approved sources. A list of approved sources will be maintained by the Department and made available from the State Materials Office.

As a minimum, each plant must provide suitable bins, stockpiles or silos to store and identify aggregates without mixing, segregating or contaminating the different sources or grades. Identification shall include DOT designated, approved pit number and aggregate grade. Measure aggregates by mass or volume within an accuracy of 1% of the required amount. Apply aggregate surface moisture corrections.

9.2.4.3.1 Wetting Coarse Aggregate Stockpiles, Storage Bins and Silos

The entire surface of the coarse aggregate shall be continuously and uniformly sprinkled with water for a period of 24 hours immediately preceding introduction into the concrete.

Any request for deviations from the 24 hour sprinkling requirement should be addressed in the Producer’s Quality Control Program for consideration by the District Materials Engineer.



(1) Coarse or Fine Aggregate: ±75 lbs/yd3 [±45 kg/m3] of concrete.


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9.2.4.4 Admixtures

• Use only admixtures approved by the Department


• Admixture dosage rate shall be within the range of the manufacturer’s technical data sheet for the product.


9.2.4.4 Admixtures

Only admixtures approved by the Department shall be used in concrete mixes. A certification from the admixture supplier that the admixture proposed meets the requirements of Standard Specification 924. Ensure that the certification also includes an additional statement from the admixture supplier or an approved independent testing laboratory that the proposed admixture is compatible with all other admixture to be included in the concrete design mix. Admixture dosage rate shall be within the range of the manufacturers technical data sheet for the product to be used.



(1) Admixtures: Shall be within the manufacturer’s technical data sheet range. Adjustments falling outside the technical data sheet range shall require design mix re-verification.


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9.2.4.5 Scales and Meters

• All scales, meters, and other weighing or measuring devices shall be checked by a company registered with the Bureau of Weights and Measures of the Florida Department of Agriculture prior to the production of concrete.

• Every 90 days


9.2.4.5 Scales And Meters

All scales, meters and other weighing or measuring devices, excluding admixture dispensers, shall be checked for their accuracy by a qualified representative of a scale company registered with the Bureau of Weights and Measures of the Florida Department of Agriculture prior to production of concrete. Scales, meters and other weighing or measuring devices, excluding admixture dispensers, shall be checked quarterly at a minimum. The Department reserves the right to be present during all scale checks.


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9.2.4.6 Batching Accuracy

• Failure to implement corrective measures will be cause for placing the plant on non-approved status and void the approval of the QC Plan.

9.2.12 Sampling and Testing of Materials

• Sampling and Testing of materials and concrete for quality control purposes is the responsibility of the concrete production facility. Meet the requirements in Table 1.


9.2.4.6 Batching Accuracy

Failure to maintain batching operations of the plastic concrete within the tolerance for each component material requires immediate investigation and corrective action by the concrete Producer, and automatically places the plant on conditional approved status. Failure to implement corrective measures will be cause for placing the plant on non-approved status and void the approval of the Quality Control Plan.


….. Table 1 designates the minimum sampling and testing frequencies that will be accepted in a well controlled production facility.


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9.2.12 Sampling and Testing of Materials Sampling and Testing of materials and concrete for quality control purposes is the responsibility of the concrete production facility. Frequency of sampling must be designed to provide adequate data to operate the quality control program for each design mix. Table 1 designates the minimum sampling and testing frequencies that will be accepted in a well controlled production facility. The quality control plan shall indicate an increased sampling rate when any quality control plan limit is reached. All sampling and testing shall be conducted in accordance with current ASTM sampling and testing methods.


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9.2.5 Design Mixes

• Form 675-010-03, Concrete Design Mix [Form 675-010-04 for metric projects] shall be used for design mix submittals.

• Make a separate submittal for each class of concrete and each particular combination of component materials to be used

• For trial mixes:• Normal weather – temperatures of 70 to 85°F [20 to

30°C]• Hot weather – minimum temperature of 94°F [35°C]

9.2.5 Design Mixes Design mixes shall meet the requirements of Standard Specification 346. Form 675-010-03, Concrete Design Mix [Form 675-010-04 for metric projects] shall be used for design mix submittals.

…The District Materials Engineer will monitor or otherwise review the proportioning, mixing and testing of the proposed mix. When the mix properties and components have been verified, the District Materials Office will so advise the State Materials Office, who will issue approval for the mix design. Those mix designs that cannot be verified regarding final properties or components will be returned to the concrete producer as unacceptable for use on Department projects. Make a separate submittal for each class of concrete and each particular combination of component materials to be used at trial mix temperatures of 70 to 85ºF [20 to 30ºC], and for hot weather mixes at a minimum temperature of 94ºF [35ºC]. Use only design mixes approved by the State Materials Office for Department use. The approved concrete mix design will remain in effect until the District Materials Office authorizes a change in writing..


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• Submittal of historical or trial mix data:

• Historical data from a minimum 15 consecutive Department acceptance tests of production concrete

• Alternatively, test data from a single trial mix demonstrating the proposed mix will have a slump within ± 0.5 inch [±15 mm] of the target value (or for mixes utilizing HRWR, within ±1 inch [±25 mm] of the target value), air content of 2.5% to 5% and strength required to meet an over design which is the minimum required strength plus 1.6 standard deviations.

9.2.5 Design Mixes

9.2.5 Design Mixes

….Include the following with the mix design submittal: ….(3) Historical or trial mix data: (a) Historical data from a minimum of 15 consecutive Department acceptance tests of production concrete, made in accordance with the proposed mix design, which demonstrates that the proposed mix has met all applicable plastic and hardened concrete specification criteria without failure. For drilled-shaft concrete to be placed in (1) a wet shaft, or (2) a dry shaft requiring a temporary removable casing, provide slump loss test results. The Department will not approve hot weather mixes based on historical data. (b) Alternatively, test data from a single trial mix which demonstrates that the produced concrete using the proposed mix, designated ingredients and designated water to cementitious materials ratio will have a slump within ± 0.5 inch [±15 mm] of the target value (or for mixes utilizing HRWR, within ±1 inch [±25 mm] of the target value), air content of 2.5% to 5% and strength required to meet an over design which is the minimum required strength plus 1.6 standard deviations.


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1,400 psi [10 MPa]> 5, 000 psi [35 MPa]1,200 psi [8 MPa]≤ 5, 000 psi [35 MPa]

Minimum Over DesignConcrete Design Strength

9.2.5 Design Mixes

• Submittal of strength test data:• Established standard deviation of the plant within

1,000 psi [7 MPa] representing at least 30 consecutive tests, or

• use over design requirement:

• Ensure that preparation and testing of trial mixes is performed by laboratory acceptable with the Department

9.2.5 Design Mixes (Cont.)

…Submit strength test data for establishing the standard deviation of the plant to meet the specified strength of the mix submitted for approval within 1,000 psi [7 MPa]. The strength test data shall represent either a group of at least 30 consecutive tests or a statistical average for two groups totaling 30 or more tests. When the Department cannot determine the plant standard deviation from historical data, apply an over design requirement, based on a singular trial mix, that is the minimum required strength plus 1,200 psi [8 MPa] for minimum required concrete strengths of 5,000 psi [35 MPa] or less. For minimum required concrete strengths above 5,000 psi [35 MPa], apply an over design requirement that is the minimum required strength plus 1,400 psi [10 MPa].

Ensure that preparation and testing of the trial mixes is performed by a laboratory acceptable to the Department which (A) has been inspected by the CCRL on a regular basis, with all deficiencies corrected, and under the supervision of a Specialty Engineer, Engineer’s representative or a professional Engineer, or (B) meets all the requirements of ASTM C 1077.

The Department may give consideration to approval of laboratories operating under other independent inspection programs demonstrated to be equivalent to the programs recognized in (A) and (B). Ensure that the 28-day strength (or strength at any other designated age) of trial mixes meets the above stated over design requirements to ensure that concrete sampled and tested at the point of placement has a strength exceeding the specified minimum strength.


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Section 9.2Concrete

ProductionFacilitiesGuideline

Any Questions

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