CONCRETE PAVING PLANT MONITOR
Review the Contract and Plans:- Become familiar with applicable specifications based upon the size of the project and delivery method of concrete.
- Review incentives and disincentives available.
- Check Schedule of Materials Control (SMC) for testing rates and sample sizes.
- Attend the pre-construction meeting if possible.
- Attend the pre-paving meeting.
- Verify the Contractor’s aggregate sources and make sure preliminary testing if required has been done well in advance of the project start date.
- Make sure the Contractor submits mix designs to the Concrete Engineering Unit for review a minimum of 21 days prior to initial placement of mix design.
- The Contractor fills out the Contact Report - Paving (CONC-403).
- Perform an on-site inspection of the plant with the Contractor.
- Review the Contractor’s concrete paving combination plant-lab office for compliance.
- Verify whether the Contractor has an electronic means of communication (email).
- Check that scales and water meter are calibrated and retain a copy of the calibration certificate.
- Obtain pre-production coarse aggregate samples for quality testing including the -#200 test in accordance with the SMC.
- Verify cement, fly ash, other cementitious materials (if used) and admixtures are on the Approved/Qualified Products list.
- Obtain cement, fly ash, other cementitious materials (if used) and admixture samples from the Contractor per the SMC. Provide sampling containers and witness sampling when possible.
- Include cementitious invoices when submitting samples to the laboratory for testing.
- Fill out lab sample I.D. cards completely and enclose them with the samples.
- Submit the signed Contact Report and certificate of compliance to the Concrete Engineering Unit for final review at: conc1off.dot@state.mn.us.
- All material and equipment changes during the construction of the project must be updated on the Contact Report and sent to the Concrete Office.
- Obtain the Contractor’s organizational chart listing names, phone numbers and emails of individuals responsible for mix design, process control administration and inspection.
- Ensure compliance with minimum and maximum mixing times.
- Inspect batch trucks for compliance with specifications. Check for mortar tightness, proper operation of box vibrators, cleanliness, and legal load limits.
- Monitor stockpiling and unloading of delivered aggregates. The stockpiles should be built long and wide and not high and on a stable base that is properly drained.
- Check the aggregate stockpiles for segregation and contamination throughout the day.
- Observe the loader operator periodically during the day for proper stockpile management. Check for contamination (e.g. clay balls) from trucks unloading or from the loader digging too deep.
- Check field hoppers for contamination. If contaminated, have Contractor empty storage and weigh hoppers and re-charge.
- Review mix designs and ensure the Contractor is using correct mix design weights.
- Check multiple times daily that batch weights are adjusted in accordance with current moisture tests, the correct mix design weights are being used and the w/c ratio is not exceeding the specification requirements.
- Ensure compliance with minimum and maximum mixing times.
- Obtain samples of cement, supplementary cementitious materials (fly ash or slag) and sand in accordance with the SMC.
- Fill out the Sample I.D. card completely and enclose with lab samples. Identify ASR sample with “Project Specific ASR Testing” on ID card.
- Verify contractor performs start-up moisture tests prior to production.
- Obtain aggregate samples for moisture testing in accordance with the SMC.
- Take additional moistures whenever moisture appearance of delivered aggregate seems to vary or batch water deviates greatly from previous loads.
- Use Concrete W/C Ratio Calculation Worksheet (CONC-409) to determine the moisture contents, water/cementitious ratio, microwave oven water/cementitious ratio, and water/cementitious ratio incentive/disincentives. The Contractor performs the unit weight and provides the results.
- Provide the Contractor with aggregate moisture results and verify that the batch ticket weights are adjusted in accordance with the moisture test results.
- Review water/cementitious ratio results for compliance with project specifications and verify with microwave oven testing.
- Obtain aggregate samples for verification testing in accordance with the SMC.
- If testing aggregate gradations in the field, use QA JMF Concrete Aggregate Workbook (CONC-411) for gradation testing, otherwise submit to the lab.
- The Contractor uses the QC JMF Concrete Aggregate Workbook (CONC-410) for both (QC and verification companion) gradation testing, and for determining JMF moving average and well-graded incentives.
- Review Contractor’s verification companion test results for compliance and compare to the Agency verification test results (split samples).
- Review the Contractor’s JMF Aggregate Summary Workbook.
- If submitting gradation samples to the lab, fill out Aggregate Sample I.D. cards including the JMF number and the Contractor’s verification companion gradation results. Identify “QA Gradation” on ID card.
- Determine if Contractor is eligible for well-graded aggregate incentives using the QC JMF Concrete Aggregate Workbook.
- Perform all percent passing the #200 (75 mm) sieve at the Contractor’s plant site.
- Sample and test in accordance with the SMC.
- Use QA JMF Concrete Aggregate Workbook to calculate the percent passing the #200 (75 mm) sieve in the field.
- Review the Contractor’s percent passing the #200 (75 mm) sieve for the coarse aggregate results to determine compliance or if additional testing is required.
- Compare to Agency results with Contractor results when testing split samples.
- Record Agency test results in the Additional Remarks/Comments within the Contractor’s QC JMF Concrete Aggregate Workbook.
- Determine when Aggregate Quality samples will be taken in accordance with the SMC.
- Fill out Aggregate Sample I.D. cards completely and record the Contractor and Agency -#200 (75 mm) test results.
- Identify Quality samples with a “Q” including the specification reference (Spec 3126 for sand and 3137.2D3 for coarse aggregate) on ID card.
- Identify the Quality Companion samples with a “Q”.
- Determine when random Coarse Aggregate Quality Incentive/Disincentive samples (Class B or Class C aggregates only) will be taken using the CA Quality Incentive/Disincentive Workbook (CONC-405) and in accordance with the SMC.
- Fill out Aggregate Sample I.D. cards completely and enclose with lab samples. Identify Incentive samples with “I/D” on ID card.
- Enter the Class B absorption results or Class C carbonate results into the CA Quality Incentive/Disincentive Workbook to determine the incentive. Using Class A aggregate is an automatic incentive, so sampling and testing is not required to determine the incentive.
Concrete Ingredient Summary:
- Collect a production summary in an electronic format from the Contractor of the daily total concrete produced and daily total ingredient quantities (aggregate, cementitious and water) including the percent overrun/underrun.
- Collect final project total quantities for concrete produced and ingredients in an electronic format including the percent overrun/underrun.
- Obtain the Contractor’s on-site QC records and charts daily or as directed by the Engineer.
- Review the Contractor’s on-site QC records and charts daily for accuracy and completeness.
- Obtain batch tickets daily or as directed by the Engineer.
- Use the Concrete Batch Plant Diary (CONC-407).
- Includes hours of production, equipment, weather, test results conducted at the plant, air temperatures, concrete yardage totals, and problems or unique circumstances encountered.
- Contact Report
- W/C Ratio Incentive Calculation Worksheets
- Well-graded Aggregate Incentive Worksheets
- Quality Incentive/Disincentive Worksheets
References: MnDOT Specification 2301, 2461, 3126, 3137, Special Provisions, Schedule of Materials Control and MnDOT Concrete Manual.