Contents

CONCRETE - GENERAL

CONCRETE - MIX DESIGN / PRODUCTION

CONCRETE - EQUIPMENT

CONCRETE - DELIVERING SAMPLES TO CHEMICAL & PHYSICAL LABS

CONCRETE - GENERAL

Q1. How do you turn in concrete cylinders with the new RFID tag?

A1. Review this RFID Entering and Tagging Presentation

NOTE: Other questions about RFID should be directed to the Materials and Tests Units Field Concrete Engineer, Material Operations Engineer or the Research and Investigations Engineer.

Q2. Who is the Area Materials Engineer (AME) in my Division?

A2. You can find your Division AME in the NCDOT Materials and Tests under the Key Staff Members in the Field Operations Section.

Q3. What is Alkali-Silica Reaction (ASR) and what aggregate sources have been known to have issues with this in concrete mixes?

A3. An explaination of what ASR is and the aggregate sources that have had issues with this is explained in this brief.


Q4. Who is responsible for calibrating Latex Modified Concrete (LMC) mixers?

A4. The Area Materials Engineer (AME) assigned to your Division is responsible for calibrating LMC mixers.


Q5. What is the Minimum Sampling Frequency for Class "B" concrete?

A5. See online Concrete Field Tech Study Guide on concrete testing frequencies.


Q6. Who do I contact with questions regarding precast concrete materials?

A6. The Field Operations section is responsible for inspection of precast concrete plants throughout the state. The NCDOT Vendor system has a database to lookup approved Precast Materials. The Structural Materials Laboratory can be contacted with any questions on precast materials. Precast plants perform their own testing of precast concrete materials. Materials and Tests also maintains a Google Map of approved Precast Producers and can be found at M&T Manufactured Products Google Maps.

Q7. Who do I contact with questions regarding prestressed concrete materials?

A7. The Prestressed Concrete Subsection of the Structural Materials Laboratory. The Prestressed Concrete Subsection is responsible for the plant inspection of all prestressed concrete products used by the Department.  Prestressed Concrete Inspectors perform 100% inspection of the production process – from tensioning, and set up of the beds to de-tensioning and final approval of the completed product. Precast plants perform their own testing of precast concrete materials. Materials and Tests also maintains a Google Map of approved Prestressed Producers and can be found at M&T Manufactured Products Google Maps.

Q8. HiCAMS won't take my Alternate ID on my Material Received Report for Precast or Prestressed Concrete materials. What do I need to do?

A8. See this Hicams FAQ for this.

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CONCRETE MIX DESIGN / PRODUCTION

Q1. Does the Form 312-R need to be signed by the contractor prior to submittal to the Mix Design Engineer?
A1. Yes

Q2.  Do test data results need to be submitted when submitting a new mix design for approval?
A2.  Yes, when there is no previous history of the mix or if any major changes are made as defined by Section 1000-3 of the specifications.

Q3.  Who needs to submit the 312-R form to the Mix Design Engineer?
A3. The projects Resident Engineer.

Q4.  How many days in advance should a concrete mix design submittal be sent to the Concrete Mix Design Engineer?
A4. A minimum of 30 days in advance.

Q5. What if the aggregate source supplying aggregate at my plant is not on the NCDOT approved list?
A5. You can not produce for NCDOT and must get an approved source to supply your plant with aggregate in compliance with NCDOT Specifications.

Q6. Do I need to record the actual batch quantities and the individual batch weights?
A6. Yes, all quantities and weights must be computer generated or hand printed, but must be recorded for each batch produced (policy letter dated August 29, 2000).

Q7. What certification do I need to batch concrete for NCDOT?
A7. All batchers who produce concrete for NCDOT, must keep a current Concrete Field Technician and Concrete Batching Technician Certification.

Q8. If my Concrete Batch Technician Certification is current, do I need to keep my Field Technician Certificate current?
A8. It is mandatory to keep both certifications current or you will have all certifications revoked.

Q9. Question: Do I need to perform a moisture content on coarse aggregate?
A9. Yes, the certified batcher is required to perform moisture contents by the drying method on both fine and coarse aggregate a minimum of twice a day or whenever deemed necessary. These moisture calculations are to be recorded, documented and stored with the producer’s copy of the batch weight tickets.

Q10. What if the moisture the batcher computes is different from the moisture the computer indicates?
A10. The batcher must have the capability to change/update the moisture contents for both fine and coarse aggregate prior to batching. This correction is to be performed at the batching facility and not at the central dispatch location.

Q11. What if the moistures are not changed in the computer?
Q11. The batcher and plant certifications will be investigated. Pending the investigation, disciplinary actions may be implemented towards the facility.

Q12. Does the batcher need to review the approved mix design?
A12. Yes, the certified batcher is responsible for all production of concrete. All sources of materials should be correct on site and approved by NCDOT. If any producer / facility source on the mix design is different than on site, you must submit a new mix design or get the approved materials.

Q13. What paperwork is required on the materials?
A13. The plant is responsible for and must supply current copies of certifications for all cement, fly ash, slag, fine and coarse aggregates, all admixtures, and the water source. In addition, all sources must be on the “NCDOT Approved List”.

Q14. How does the DOT keep track of mix designs?
A14. By use of two electronic databases. The Concrete Mix Design database is a plant-by-plant list of mix designs accepted for each plant. Data on each mix design includes mix number, class, proportions, mix properties, material sources, and material properties. Acceptance of a mix design in this database does not constitute its acceptance for any contract. Assignment of mix designs to contracts involves a separate submittal, review and acceptance procedure via the Concrete Mix Contract Assignment database. Mix designs must be in the Concrete Mix Design database to qualify for assignment to a contract.
Upon written request from the Engineer for specific mix designs to be assigned to a contract, the Physical Testing Engineer reviews and assigns these mix designs in the Concrete Mix Contract Assignment database. This database shows the list of mix designs assigned to each contract. Requests for mix design approval for contracts outside the scope of HiCams are handled similarly except that the Concrete Mix Contract Assignment database is not used, in which case approved hard copies are returned to the Engineer for distribution.

Q15. How do I submit a mix design for the Mix Design database?
A15. Complete Materials and Tests Form 312U (English units only) and e-mail it to the Concrete Mix Design Engineer and carbon copy the Structural Materials Laboratory Supervisor.

Q16. How do I submit mix designs for a contract?
A16. It is the contractor’s responsibility to submit such requests to the DOT Resident Engineer administering the contract. The contractor should request the concrete producer to complete M & T Form 312R, Mix Design Request Form, for each plant he plans to use to supply concrete and forward these forms to him for submittal to the Engineer.

Q17. My ACI Certification is good for another year, but my Field Technician certification expired this year. May I continue to test concrete and batch concrete for another year (provided my Batch Certification is good for another year)?
A17. Once the Field Technician Certification expires, all DOT certifications associated with it expire. While the ACI certification may still be current, NCDOT requires a current Field Technician certification for testing sampling and producing concrete. The ACI is a component of the Field Technician certification.

Q18. My truck driver who is field tech certified informed me the concrete was not sampled properly during acceptance testing by project personnel. What should I do?
A18. Once an error of this type is exposed, immediately notify the project personnel. In addition, inform the M&T Concrete Technician of the problem. Document the specific procedure you feel was run incorrectly. Keep a record including date, ticket number, project, and structure where the concrete is placed.

Q19. Do I physically have to be present in the batch room when concrete is batched for a NCDOT project? May I be on the premises, monitoring the batch process via two-way radio?
A19. The batcher must be physically present during batching of concrete on a NCDOT project. The certified batcher should be the one actually batching the concrete, not supervising someone who is not certified.

Q20. I just discovered the wrong mix design was used to batch concrete for a NCDOT project. Whom do I notify about this mistake? Will I lose my certification?
A20. Once an error of this type is discovered, immediately notify project personnel. The M&T concrete technician should also be informed of the error. Depending on the circumstances, the error will not necessarily lead to loss of your certification. The batcher should still maintain all required documentation. The M&T 903 form should reflect the mix design that was used. The worst possible thing to do in this case is to attempt to alter records to cover up the mistake.

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CONCRETE EQUIPMENT

Air Pots

Q1. How do NCDOT employees order Air Pots and other concrete field sampling equipment?

A1. Air Pots can be ordered using the Concrete Air Pot Request Form. Division Personnel are strongly encouraged to contact their Division Section Materials Specialist when ordering Air Pots. Other Concrete Equipment can be ordered through the Materials and Tests Stockroom using a Master Form M&T 100 (Requisition Form).

Beam Breakers

Q1. How much advance notice is required to request for delivery, setup, and calibration of a flexural beam machine?

A1. 2 weeks minimum advance notice is requested by email to the Structural Materials Laboratory Supervisor.

Q2. How long is a calibration good for?

A2. A calibration is good for a year as long as the flexural beam machine has not been moved. A 2 weeks’ notice for recalibration is required by email to the Structural Materials Laboratory Supervisor.

Q3. Can a beam machine be relocated after calibration has been performed?

A3. No. Once a machine is moved the original calibration becomes void and a recalibration is necessary.

Chase Indicators

Q1. What is the procedure for getting chase indicators calibrated?

A1. Contact the Structural Materials Laboratory Supervisor via email at least 48 hours in advance. At the time of delivery, up to 25 new chase indicators can be swapped out, eliminating the need for a return trip to pick up the chase indicators.

Q2. Can more than 25 new chase indicators be dropped off for calibration?

A2. Yes. Contact the Structural Materials Laboratory Supervisor via email. It could take up to 10 business days for more than 25 chase indicators to be calibrated as the laboratory may not be able to swap out more than 25 chases indicators at one time.

Q3. Can used chase indicators be re-calibrated?

A3. Yes. Contact the Structural Materials Laboratory Supervisor via email. Please allow at least 10 business days for chase indicators to be recalibrated.


Q4. Where can I drop off my chase indicators for calibration and recalibration?

A4. Chase indicators can be dropped off at the Structural Materials Laboratory Office (previously the Concrete Laboratory Office) at 1801 Blue Ridge Road. Please contact the Structural Materials Laboratory Supervisor via email prior to dropping off or swapping chase indicators out.

Turbidimeters

Q1. How frequent are Turbidimeters calibrated?

A1. Turbidimeters should be calibrated every 6 months. Turbidimeters can be dropped off to the Structural Materials Laboratory- Chemical Sub-section lab or sent via Courier Mail: 1563MSC. Attn: Structural Materials Laboratory Supervisor.

Q2. How will I know that my Turbidimeter is due for a calibration?

A2. Each Turbidimeter has a sticker with the expiration date. A calibration is good for 6 months. An email is also sent to the point of contact stating that the meter is due for calibration.

Q3. How long does it take to have my Turbidimeter calibrated?

A3. Please allow 3 business days for your Turbidimeter to be calibrated. Sending your Turbidimeter via Courier service could extend the amount of turnaround time for you to receive your calibrated meter.

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DELIVERING SAMPLES TO CHEMICAL & PHYSICAL LAB

Q1. What happened to the Chemical and Physical Laboratories?

A1. The Chemical and Physical Laboratories are now sub-sections of the Structural Materials Laboratory under the supervision of the Structural Materials Laboratory Supervisor.

Q2. Where do I deliver samples for the Chemical and Physical Laboratories?

A2. The samples for the Physical Lab should still be delivered to the Concrete Laboratory of the Physical Lab. Samples for the Chemical Lab with the exception of Paint, Chlorides and Asphalt Binder samples should be physically delivered to the Concrete Lab.


Q3. If I am physically delivering the Chemical Lab’s samples to the Physical Lab can I note this in HiCAMS?

A3. No. Chemical Lab samples should be submitted to the Chemical Lab in HiCAMS.

Q4. What is the typical testing turnaround time for samples submitted to the Structural Materials Laboratory?

A4. The typical testing turnaround times vary for each sample. See Lab Testing Services.

Q5. How should RFID tags be attached to samples coming to the Structural Materials Laboratory?

A5. See the RFID procedures.

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Materials & Tests Materials and Tests Manual FAQ

Materials & Tests
Materials and Tests Manual FAQ