Ready-Mix Concrete - Plant Monitor

Weeks Prior to the Project Start Date

  • Review Plans to determine project quantities and mix types 
  • Review the Special Provisions
  • Review the Project Schedule of Materials Control listed in the Contract o Review Certified Ready-Mix Concrete testing rates
    • Quality Assurance (Agency) testing rates
    • Quality Control (Producer) testing rates
  • Attend the Pre-Construction meeting to determine concrete supplier 
  • Check to see if the plant is certified on the MnDOT Concrete Engineering website  o If it is not certified, contact the MnDOT District Independent Assurance Inspector ASAP
  • Request mix designs from the Producer o General Mix Design Sheet (RMX XXX-XXX) o Project Specific Mix Designs (JMF XX-XXX or PS XX-XXX)

Days Prior to the Project Start Date

  • Review the Contact Report and Site Map o Ensure cementitious materials listed on Contact Report are still being used.
    • If not, verify new materials are on MnDOT’s APL and obtain a sample and submit to the Maplewood Lab and request the Contact Report be updated and submitted to MnDOT Concrete Office.  Obtain a copy of the supplier’s delivery invoice
    • General mixes allow for cementitious substitutions if they are listed on the APL.  In contrast, Project Specific Mix Designs are required to use all components listed on the mix design

o Ask the Producer which admixtures they intend to use in the mix
§ Verify admixtures are listed on the Contact Report and are listed on the APL.

  • Producers can use any admixture for General Mixes with the exception of Types C and E.  Types C and E admixtures require the approval of the Concrete Engineer/Project Engineer
  • Project Specific Mix Designs must have admixtures and dose rates listed on the mix design.  Some admixture dose rates on the mix design may

be listed as 0 oz - xx oz/cwt so the Producer may elect to not make use of them
o Determine which aggregates will be used on the project, review stockpile locations on the Site Map, and check stockpiles for contamination, segregation, and interblending
(Always check in with the Batch Person prior to Stockpile Inspections and Sampling)
•    Review the Producer’s Quality Control Charts and Sample Log to determine if aggregate Monthly Quality samples are due (Last submitted Monthly Quality more than 30 days prior).  

Day of the Plant Inspection

Plant Inspection Responsibilities

  • Verify the plant is Certified and listed on the MnDOT Concrete Engineering website  
  • Ensure the Producer is using a MnDOT signed General or Project Specific Mix Design sheet o Approved General Mix Design Sheet numbers will be listed on the Concrete Engineering

Unit’s website at: https://rmx.dot.state.mn.us/rm_mix/o Project Specific Mix Designs must have your project listed on the mix design sheet

  • Observe that stockpiles listed on the approved mix design are being used in the mix                 
  • Check stockpiles for contamination, segregation, and interblending                             
  • Review the Moisture Tests tab in the QC Workbook to ensure the Producer’s current moisture test results are entered into the batching system 
  • Observe one load of concrete being batched to ensure the Total Water is less than Design Water by using the Certificate of Compliance Check tab in the QA Workbook  
  • Observe the QC Tech perform gradation tests if possible                                                  
  • Observe the QC Tech perform moisture tests if possible                                                

Certificate of Compliance Review

*Note:  This is a partial list of required information on a Certificate of Compliance.  Please refer to the Contact Report, Supplemental Specs and Spec 2461.3F.2 for a complete list of requirements.

  • Plant name and Location/address
  • Project and/or Bridge Number
  • Approved Ready-Mix (RMX) Sheet Number (XXX-XXX)
  • MnDOT Mix Designation
  • Date/Time of Batch
  • Cubic Yards
  • Cubic Yards daily cumulative
  • Correct Aggregate sources (MnDOT pit number)
  • Total Moisture Factor (MCFac) matches line F from the most recent moisture test
  • Absorption Factors (AbsFac) for each aggregate match the mix design
  • Weights listed in the OD column match the mix design
  • Weights listed in the Actual column are within tolerance of the Target Weights as verified on the Certificate of Compliance Check tab in the QA Workbook
  • Producer must review the first ticket for each mix type each day and:
    • Print their name and Tech ID Number o Hand sign their name in the designated location

Electronic Documentation

  • The Producer’s QC Workbook has been reviewed for completeness and accuracy  o Gradation Test results and rates o Moisture Test results and rates
  • The Producer’s Control Charts and Sample log are accurate and complete
  • Verify all samples have been taken in accordance with the Schedule of Materials Control
    • Aggregates (Monthly Qualities, Verification, and QA Samples)
    • Cementitious Materials
    • Admixtures
  • Any gradation performed by the Producer that has failed was immediately retested  o ALL FAILING QC GRADATIONS REQUIRE A SECOND TEST TO BE IMMEDIATELY TAKEN o STOP PRODUCTION AND CONTACT THE ENGINEER IF THE SECOND GRADATION FAILS OR

THE MOVING AVERAGE IS OUT

Verify both the failing and passing results have been charted in the Producer’s Control Charts

  • Fill out the Weekly QA Workbook completely and accurately                                          
    • Review the Inspection Checklist tab o Fill out a Certificate of Compliance check every time a plant inspection is performed
  • Review QC Workbook for minimum sample sizes, overloaded sieves, and unreasonable results

Sampling and Testing

  • Collect cementitious and admixture samples per the rates in the Schedule of Materials Control
  • Obtain Verification and QA samples per the rates in the Schedule of Materials Control
  • Document Verification test results for each aggregate size and source on the aggregate summary
  • Document Verification Companion test results on the Aggregate Summary tab of the QA Workbook
  • Compare Agency test results with the Producer's companion results for lab/field tolerances

Discrepancies, Issues and Non-Compliance

  • If any equipment malfunctions, testing procedures or test results are questionable, or unusual activity is occurring during the plant visit perform the following:
    • Continue monitoring at the plant and document observations in the diary o Investigate to determine the origin of the concern and document the resolution o Contact Independent Assurance Inspector, Project Engineer, or Concrete Engineering Unit when necessary
  • If the Engineer observes the Producer not complying with the requirements of the Certified Ready-Mix Plant Program, the Engineer may perform the following:
    • Verbally notify and promptly email the Producer and the Concrete Engineer the list of observed deficiencies and provide a deadline to correct the non-compliance.
    • If non-compliance is not corrected by the deadline, notify the Contractor and Producer that concrete production is unauthorized in accordance with 1512, “Unacceptable and Unauthorized Work.”

 
IF THERE ARE ISSUES AT THE PLANT, DOCUMENT THEM IN THE QA DIARY AND LET SOMEONE KNOW!

Contacts

Brad Swenson – Greater Mn Plant Specialist Northern Region – Districts 1, 2, 3A, 4
Cell: 218-232-1012
bradley.s.swenson@state.mn.us

Mike Daniels – Greater Mn Plant Specialist Southern Region – Districts 3B, 6, 7, 8
Cell: 320-293-9421
michael.daniels@state.mn.us

Matt Herbst – Plant Specialist Metro Region
Cell: 651-283-7127
matthew.herbst@state.mn.us

Gordy Bruhn – Field Engineering Specialist (Field issues – Low Cylinder Strengths – Paving Rehab)
Cell: 651-398-9597
gordon.bruhn@state.mn.us

Jake Gave – Assistant Concrete Engineer - Structural, High Performance, SCC, and Mass Concrete
Cell: 612-554-9289
jacob.gave@state.mn.us

Rob Golish – Assistant Concrete Engineer – Paving, Joint Layouts, Approved/Qualified Products
Cell: 651-216-0516
robert.golish@state.mn.us

Maria Masten – Concrete Engineer – Specs, Standard Plans, Material Failure Recommendations
Cell: 651-334-4015
maria.masten@state.mn.us

MnDOT District Independent Assurance Inspectors (IAI)

D1 Duluth - Nadine Miller - (218) 348-6297
D2 Bemidji -Raymond Wesley - (218) 766-6949
D3 Baxter - Matt Miles - (218) 232-6748
D4 Detroit Lakes - Casey Clarke - (218) 849-7393
D6 Rochester - Dennis Hayes - (507) 251-0138
D7 Mankato - Mitch Jordahl - (507) 380-9619
D8 Willmar - Paul Janke - (320) 212-5739
Metro/West - Karl Sinclair - (651) 775-0998
Metro/East - Kaleb Kollmann - (651) 478-0339
Metro/East - Kris Westerbur - (651) 775-1151
Metro/West - Zach Lyrek-Hanks - (651) 775-1018
Metro IA Office - (651) 234-7356