1002 - Contractor Quality Control for Concrete
GENERAL
1002 - Contractor Quality Control for Concrete
Contractor Quality Control for Concrete requires that the Contractor provide and maintain a Quality Control Plan, listing all the personnel, equipment, supplies, and facilities necessary to obtain samples, perform tests, and otherwise control the quality of the product to meet specified requirements.
The Quality Control Plan provides the Engineer with a work plan describing the methods and means of assuring that the associated concrete items are constructed according to specification requirements. Furthermore, the Quality Control Plan provides the Contractor with guidance so that the appropriate measures are taken to sample and test the concrete, administer the actions necessary to ensure that only concrete conforming to specification requirements is incorporated into the project, and provide the Engineer with valid documented results in a timely manner.
MDOT will not sample, nor test for quality control or assist in controlling the Contractor’s production operations. However, compression strength tests on the concrete products will be performed by the Department according to QA specification requirements.
Furthermore, the Contractor will not be permitted to continue production of nonconforming work at a reduced price, in lieu of making the necessary adjustments to bring work into conformance.
Failure of the Contractor to provide properly documented QC test results in a timely manner is justification for withholding acceptance and payment for the concrete product.
Communication between MDOT and the Contractor’s QC staff is critical to the success of the QC/QA project.
The Engineer reserves the right to require that the Contractor submit an updated Quality Control Plan, whenever warranted.
Responsibilities
The responsibilities of each party must be clear at the start of the project.
Contractor Responsibilities
Develop and maintain a Quality Control Plan to inform all involved exactly how QC will be administered for all materials, equipment, and work methods used to construct the items on the project. The Quality Control Plan must ensure the materials, equipment, and work methods meet the requirements of the specifications for both on-site and off-site operations.
Submit the Quality Control Plan for the appropriate items to the Engineer for review, a minimum of ten working days prior to the start of related work.
Ensure that the Quality Control Plan is approved by the Engineer prior to placement of any concrete.
Provide the personnel and testing equipment capable of performing the specified tests for QC, interpreting results, and making required adjustments to the mix and concreting operation.
Delegate the QC Administrator full authority to institute any and all actions necessary for the successful implementation of the QC plan.
Provide the Engineer prior notification of all QC testing, and the opportunity to witness all sampling, testing, and measurements.
When directed by the Engineer, sample and test any material which appears inconsistent with similar material being sampled. However, testing of this material is not necessary if the Contractor voluntarily agrees to remove and replace the defective concrete.
Reject materials not meeting specification requirements.
Maintain complete records of all QC tests and inspections.
Provide the Engineer records of QC tests and inspections within 24 hours after testing or inspection in a format acceptable to the Engineer.
Update the Quality Control Plan to reflect any changes in the work, or to correct unsatisfactory performance, as required by the Engineer.
MDOT Responsibilities
Familiarize yourself with the QC/QA specifications.
Review the Contractor’s Quality Control Plan making sure that it identifies the individuals responsible for QC administration and testing, using the Quality Control Plan Check Sheet (Figure 604-1).
Review the Contractor’s Quality Control Plan making sure proper QC testing, inspection, and documentation are clearly defined for all phases of the work, for both on-site and off-site operations, using the Guidelines for Quality Control Plan Review by MDOT.
Assure the Contractor follows the approved Quality Control Plan.
Verify that the individual field tests are listed on the Quality Control Plan and are qualified.
Check results of QC testing and verify that the Contractor is incorporating only concrete that meets specification requirements.
Schedule and conduct an on-site pre-paving meeting.
If the Contractor fails to follow the approved Quality Control Plan, notify the Contractor’s QC Administrator and the Engineer.
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GENERAL INFORMATION | ||
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CONTRACTOR’S NAME |
PROJECT NAME | |
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CONTROL SECTION NO. |
JOB NO. | |
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PERSONNEL QUALIFICATIONS | ||
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NAME |
QUALIFICATION | |
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Possession of one of the following credentials will be considered qualified:
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NAME |
QUALIFICATION | |
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Possession of one of the following credentials will be considered qualified:
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EQUIPMENT AND FACILITIES | ||
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SERIAL NO. |
TYPE |
CALIBRATION PROVIDED YES/NO |
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Description of curing facilities given |
Acceptable? Yes / No | |
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Description of how samples will be handled |
Acceptable? Yes / No | |
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SERIAL NO. |
TYPE |
CALIBRATION PROVIDED YES/NO |
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SAMPLING SYSTEM | ||
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The special provision for Contractor quality control lists minimal testing required. | ||
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Yield |
After the start of the first concrete operation for each mix design, determine yield. |
Acceptable? Yes / No |
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Slump |
At the start of the placement, test first load (subsequent loads, if required). During concrete placement, test for slump at least once per hour. |
Acceptable? Yes / No |
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Air Entrainment |
At the start of the placement, test first load (subsequent loads, if required). During concrete placement, test for air content at least once per hour. |
Acceptable? Yes / No |
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Temperature |
At the start of placement, test first load (subsequent loads, if required). During concrete placement, test for temperature at least once per hour. |
Acceptable? Yes / No |
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Strength |
Determine the strength at least once every 200 yd.3 for a specific mix design. A single strength test consists of two cylinders, or two beams. |
Acceptable? Yes / No |
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ADMINISTRATION | ||
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PERSON REJECTING CONCRETE |
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WHOM THIS PERSON WILL NOTIFY |
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CONTRACTOR’S REPRESENTATIVE (SIGNATURE) |
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Quality Control Plan
The Quality Control Plan must:
- Stress quality and commitment to job control.
- Provide written assurance that all work will be performed according to the specification requirements.
- Include a statement that the Contractor is responsible for all plan specification and special provision requirements and that the Quality Control Plan will be maintained and followed at all times.
- Include the Contractor’s current organizational chart, including lines of authority, and duties and responsibilities for each employee. The names(s) and credentials of the Contractor’s QC Administrator and QC testing technicians must be submitted to the Engineer.
- The QC Administrator must be identified and be a full-time employee of, or a consultant engaged by, the Contractor. The QC Administrator must be:
- A professional Engineer currently registered in the State of Michigan.
- Certified by the National Institute for Certification of Engineering Technologies (NICET) at Level III, or above for concrete.
- Certified as a Concrete Technician Michigan Level II through a program certified by Michigan Concrete Association Board of Examiners, or the Michigan Concrete Paving Association.
- The concrete testing must be performed by Concrete Technician(s) certified as either:
- Michigan Concrete Association (Michigan Level I or II).
- Michigan Concrete Paving Association (Level I or II - three year certification).
- List all equipment, supplies, and facilities to be used to obtain samples, perform tests, and otherwise control the quality of the product to meet specifications.
- Certify in writing to the Engineer that the testing equipment to be used is properly calibrated. All equipment should be calibrated annually. However, if any equipment is shown to be in poor condition, or improperly cleaned and maintained at any time between calibrations, it should be rejected regardless of proof of current calibration. The Contractor should then have the equipment either replaced, or repaired and calibrated prior to use.
- Include calibration data and correction factor information, which must be visibly displayed on all testing equipment.
- Specify a random method of sampling that assures all materials being produced have an equal chance of being selected for testing. Sampling and testing frequencies for all tests (yield, slump, air entrainment, concrete temperature, and strength determination) must be included.
- Itemize the actual breakdown of lots of concrete, listing their respective sampling and testing rates, for each concrete item, based on the anticipated sequence of operations for the project.
- Specify what actions will be taken by the Contractor to reject the concrete and/or make the appropriate adjustments at the batch plant when test results identify concrete that is not in compliance with the specifications.
- Specify what actions will be taken related to project site conditions for air temperature, wind speed, and relative humidity that may adversely affect environmentally induced damage to the concrete (such as a thermal gradient and excessive surface evaporation condition) that would cause uncontrolled/random cracking or premature surface deterioration of the pavement or structure. Detailed procedures and precautionary measures should be included related to monitor of concrete mixture properties and providing standby protection for the concrete during adverse environmental conditions to minimize the increased potential for shrinkage cracking.
The plan should include detailed information documenting that the specification requirements described in Section 601 of the Standard Specifications for Construction related to batch plant certification and concrete mixture criteria will be followed and that the necessary records and reports will be provided to the Engineer prior to concrete placement.
If the project is covered by the Department’s concrete quality assurance program, the Quality Control Plan must include the information necessary to provide both MDOT and the Contractor with the appropriate guidance as to how the specification requirements for quality assurance for concrete will be administered.
The quality control records must:
- Include sufficient information to allow the test results to be correlated with the items or work represented. All test results must include documentation referencing the exact locations where the tests and samples were taken.
- Include the lot identification number which coincides with the appropriate quality assurance lot identification number. This will allow all information to be correlated if a dispute arises. Quality assurance test results and identification references must be submitted on a testing form, acceptable to the Engineer, in an organized and legible format.
- Indicate what action was taken to correct deficient concrete when QC tests indicate the concrete was not in compliance with the specifications. All documentation of deficiencies and the associated actions for resolution must be logged and submitted in an organized and legible report format.
- Be furnished to the Engineer (all originals and one copy) within 24 hours after the date covered by the record. Reports and forms must be in a format acceptable to the Engineer.
MATERIALS
Calculating Adjustments
The concrete quality assurance Special Provision provides step-by-step calculations for figuring the payment on each lot of concrete. This evaluation requires that the strength results be compared to the class design strength and that the estimated percent of defective material does not exceed the rejection limit. Most offices also have a computer program to run these calculations. The key to this quality analysis is the standard deviation.
Standard Deviation Calculation
Standard deviation gives a measure of the variability of a group of test results. The following example explains how standard deviation is calculated. Most calculators will make this calculation.
S = Standard deviation of the strength test results for the lot.
Σ = Summation.
x = Individual test result (average strength of a test cylinder pair).
ẋ = Average lot strength.
n = Number of individual test results for the lot.
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(Xi - ALS)2 |
SUM |
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25.1
25.8
23.7
26.8
27.6
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(24.96 - 25.79)2
(25.86 - 25.79)2
(23.65 - 25.79)2
(26.82 - 25.79)2
(27.65 - 25.79)2
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0.49
0.00
4.41
1.00
3.24
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ALS = 25.80
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SUM = 9.14
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NUMBER OF SAMPLES n = 5
Use a standard deviation of 1.5 Mpa in your QA calculations.
Reviewing Mix Designs
The Contractor is responsible for providing a Job Mix Formula (JMF), submitted on Form 1976, for all concrete used on the project. Before production begins, all JMF must be reviewed by the Engineer. Form 2000, which can be found on the MDOT forms webpage, has been developed as a tool for this review process.
A JMF can be based on past experience with the same or similar materials and proportions, or may be based on trial batches. A Contractor may reference an old MDOT JMF, but this does not relieve the Contractor of any responsibility of providing all documentation.
All materials used in concrete must meet the acceptance criteria specified by the Materials Source Guide. A part of reviewing a JMF is to verify that aggregates, cements, and admixtures are all from approved sources, or have been tested and approved for use.
Minimum JMF criteria, such as water to cementitious ratio (w/cm) and total cementitious content are specified and must be documented in the JMF submittal. Each JMF must be accompanied by compressive strength test results which serve to give the Engineer reasonable assurance that the mix is capable of meeting the required 28-day strength.
Questions regarding JMF review may be directed to the Region materials staff or the Construction Field Services Support Area.
Meet with the Contractor’s QC personnel each production day to discuss lot sizes and sampling of the concrete. Based on the Contractor’s estimated production and whether the particular concrete placements are PWL, Non-PWL, or Small Incidental Quantities, determine the sampling rate and locations.
During the day’s placement, advise the Contractor when it is necessary to perform QA tests per 12SP604B.
Observe the placement of the concrete and request that the Contractor’s QC staff take additional QC tests when the material quality is in question. Additional QA tests may be requested and taken at any time as well.
Concrete_JMF_Yield_Calculator.v3.4-17-13.xls
- Check handling of ramp traffic, flagging operation(s), staging requirements.
- Check grade of forms and whether they are locked and perpendicular.
- Check dowel size, alignment, layout, level, height, secured, assembly, spacing for expansion joints: felt size, caps in proper position.
- Check performance per specifications, test sections per specifications, and wet checks per specifications.
- For minimal segregation, check spreader, material transfer device, direct placement, voids and/or cold joints, proper consolidation, proper head of material at screeds, minimal use of finish water, proper night and end header installation.
- Check for depth, width, alignment, raveling, spalling.
- Widening cut (transverse and longitudinal) (check for depth; width, alignment; raveling; spalling).
- Contraction joints (neoprene size; adequate adhesive; side adhesive) Expansion Joints (felt size, check for voids, sealant type, and thickness).
- Record truck number, batch/discharge time, slump, air, number of cylinders.
- Check mix design, age, beams/cylinders, strength, weather.
CONSTRUCTION
-Reserved-
MEASUREMENT AND PAYMENT
Contractor Quality Control for Concrete Pavement Warrenties
Special provisions currently govern requirements for Contractor Quality Control on projects containing warranties for concrete pavement. These special provisions will be in the project proposal.
Responsibilities
The responsibilities of each party must be clear at the start of the project.
Contractor Responsibilities
- Comply with all Contractor responsibilities described above.
- Comply with all plan specification and special provision requirements.
- Develop and maintain a Quality Control Plan to inform all involved exactly how QC will be administered for all materials, equipment, and work methods used to construct the items covered by the pavement warranty. The Quality Control Plan must ensure the materials, equipment, and work methods meet the requirements of the specifications for both on-site and off-site operations.
- List contract items covered under the Quality Control Plan (i.e.; all pavement warranty items).
- Comply with all requirements of, and modifications to, Section 602 of the Standard Specification for Construction, as well as the Authority of the Engineer in subsection 104.01 of the Standard Specifications for Construction.
- Inspect the workmanship on warranted items to ensure they meet the specifications.
- Correct any deficiencies in equipment and/or work methods and document the corrections.
- Provide the Engineer with all incentive calculations.
- Measure and document quantities for all warranted items.
MDOT Responsibilities
- Determine which contract items are covered by the warranty.
- Familiarize yourself with the QC/QA specifications.
- Familiarize yourself with the contract provisions related to Contractor QC for these items.
- Review the Contractor’s Quality Control Plan. Make sure proper QC testing, inspection, and documentation are clearly defined for all phases of the work, for both on-site and off-site operations (see Typical Acceptable QC Plan for the Inspection Work, included below).
- Require the Contractor to correct all deficiencies in the Quality Control Plan.
- Approve the Quality Control Plan once it is determined to be satisfactory.
- Schedule and conduct an on-site pre-paving meeting.
- Monitor the Contractor’s QC work to ensure that the Contractor is following the approved Quality Control Plan.
- Visit the work site often enough to reasonably assure that the Contractor is performing work in accordance with the Quality Control Plan and that the Contractor’s paving operations are in the compliance with acceptable levels for workmanship.
- Review all documentation submitted by the Contractor.
- Perform and document independent testing, inspections, and measurements to ensure the Contractor’s Quality control Plan is satisfactory (use the MDOT Checklist for Concrete Paving with Warranty).
- Perform acceptable testing per QC and QC/QA specifications.
- Require the Contractor’s QC Administrator to correct any errors and omissions in testing, inspections, measurements, and documentation.
Pavement Acceptance
Upon completion of the contract items covered by the warranty, and prior to opening to traffic, the Engineer, along with the Contractor, must conduct an on-site inspection of the warranted pavement items to determine if any visible defects or cracking exists. The respective special provision(s) in the contract proposal describe the corrective action required by the Contractor is cracking is found to have occurred. Project staging may require multiple inspections and, therefore, multiple acceptance dates of construction may be required. When the Engineer determines that the work is in compliance, the form titled “Initial Acceptance for Pavement Warranty” must be completed and distributed as required in the form.
Prior to granting initial pavement acceptance, the Engineer should confirm that all test results, certifications, and documentation are received and reviewed for each of the warrantied items.
Documentation
All Contractor and MDOT documentation must be retained at the TSC office throughout the duration of the warranty period.
If warranty work is not required, all records may be closed out and sent to the Records Center as required by current MDOT practices and procedures.
If warranty work appears necessary, the records must be retained at the TSC office until the Contractor completes the repair work and any disputes between MDOT and the Contractor are resolved by a decision of the Conflict Resolution Team (CRT).
Typical Acceptable QC Plan for the Inspection Work
The Contractor should include a list of items the Quality Control Inspector checks throughout all phases of construction operations. The Contractor should provide the Engineer with a respective checklist, form, or report for each phase of construction inspection, which must include, but is not limited to the following:
- Example of the Contractor’s Daily Report identifying:
- Equipment used
- Mix design
- Paving schedule; start and stop times, pour locations and types
- Dowels
- Tie bars
- Texturing
- Tining
- Curing
- Transverse and longitudinal saw cut time and types
- Type of seal for transverse and longitudinal joints
- List type of supplemental forms used to document the following:
- Materials handling
- Paving inspection (see below)
- Joint inspection (see below)
- Truck delivery times and tests
- Interim cylinder breaks
- Interim beam breaks
- Paving inspection forms. Typical items addressed:
- Inspector and date locations
- Weather
- Subbase (OGDC) Condition
- String line
- Forms
- Grade/Locked/Perpendicular/Supported/Line
- Equipment
- Pour width
- Cure/texture machine (including spacing, alignment, spray pattern)
- Batch trucks (check for cleanliness)
- Dowel baskets
- Check dowel size, alignment, layout, level, height, secured, assembly, spacing for expansion joins, felt size, and caps in proper position.
- Dowel bar inserter equipment interim checks during paving
- Tie bars
- Horizontal spacing for all types
- Edge slump
- Crown
- Alignment of slab
- Vertical face
- Tining
- Texture of surface
- Curing; type/coverage/uniformity
- Concrete placement method
- Computed yield
- Comments on above items
- Joint Inspection Report. Typical items addressed:
- Date/Inspector/weather
- Sawing
- Relief cut (approximate time after placement)
- Transverse (depth/width/alignment, raveling/spalling)
- Longitudinal (depth/width/alignment, raveling/spalling)
- Widening cut
- Transverse (depth/width/alignment/cleanliness/sand blast)
- Longitudinal (depth/width/alignment/cleanliness/sand blast)
- Sealing
- Transverse Contraction (neoprene size/adhesive/adherence/per specs)
- Expansion (form size/sealant/thickness)
- Longitudinal (sealant/properly placed)
- Comments on above items
- Report of placement of concrete.
- Weather
- Date
- Location
- Inspector
- Truck number
- Batch
- Time of placement start and finish
- Slump
- Temperature
- Air
- Number of cylinders
- Report of concrete strengths (cylinder or beam) for interim open-to-traffic.
- Includes slump/air/temperature/air placed/mix design
- 1/2 - 3 - 7 - 28 day strengths
- Report of concrete tests. Addressed in the QC/QA requirements for concrete.
- Pre-work coordination.
- Nature of work
- Methods
- Contract requirements
- Submittals
- Prepatory steps
- Test procedures. (As needed to fulfill QC/QA for Concrete and CQC Specification).
- ASTM C___ tests for concrete
- Acceptance testing to be performed by MDOT per requirements
- Sampling and testing frequencies
- Other tests for joint steel, epoxy, hot pour, neoprene, cure
Reporting Deficiencies and Noncompliance with the QC Requirements
- QC Administrator immediately notified
- Investigates and produces written descriptions
- Log of deficiency
- If portions of pavement cannot be brought back into conformance, then a recommended corrective action is made
- If confirmed, then notice to MDOT Engineer, with recommendation of action to be taken
- Approval by MDOT Engineer to take action before start
- QA Administrator to supervise inspection of corrective work
Minimum Record Keeping and Documentation for CQC
Review file system including approvals of submittals, methods, inspection and test reports, deficient work corrections, test procedures, changes and modifications, material storage, records, quality verification, meeting minutes, Contractor IDR’s, acceptance of work completed, qualifications of inspectors
Submittal Review and Schedule
Review the time frame for review, log, fix, and transmittal of all required submittals and test reports, including subcontractors.
Audit Procedures
Time that checks are made on all CQC documents, subcontractors, and material suppliers utilizing a proposed checklist to review all CQC inspection of workmanship and all material CQC records for adequacy and accuracy.
Qualifying Personnel
Review description and proof of qualification for all quality control technicians and their previous experience.
Retest and Coring
The Special Provision provides for retesting or coring a lot of concrete, if the strength requirements are not verified by initial compressive strength cylinders. The series of decisions leading to corrective action is summarized in the flowchart in Section 605, Figure 605-3.
