Miscellaneous Concrete Construction

  • Review Contract and Plans:
    • Become familiar with applicable specifications for the type of work performed.
    • Attend the pre-construction meeting if possible.
  • Prior to placement of concrete:
    • Review Contractor’s equipment and forms for contract compliance.
    • Ensure plan dimensions are met.
    •   Make sure Contractor has made adequate arrangements for proper curing and protection of the concrete.
    • Obtain equipment for slump and air tests, cylinders, and temperatures.
    • Check vertical and horizontal alignment.  Make sure forms are complete and adequately braced to correct line and grade.
    • Inspect grade for slope, adequate compaction, and proper moisture.
    • Review requirements for reinforcing steel, tie bars, expansion joints, and contraction joints.  Verify reinforcing steel is tied securely and in the proper position.
    • Check location from offset stakes.  Verify ADA ramp and driveway locations.
    • Verify conduits, brackets or other openings or attachments are securely in place.
    • Ensure that proper drainage conditions are met.
  • During placement of concrete:
    • Check on placement of concrete throughout the pour to see that concrete is placed without segregation, and that vibration and consolidation are adequate. 
    • Visually check delivered concrete for load-to-load consistency.
    • Document any water added or admixture additions made. Retest as per the Schedule of Material Control.
    • Do not exceed the allowable time limits for concrete placement. (Typically, 90 minutes)
  • Collect and initial all Certificate of Compliances (Batch Tickets): 
  • Verify all the information printed on the Certificate of Compliance is correct:
    • Verify S.P. Number
    • Verify Mix Number
    • Verify delivery time is within Specifications
    • Verify Water – Total Actual Water vs. Mix Design Water
    • Verify whether or not water is allowed to be added.
    • Record any additional water that was added at the job site.
    • Verify MnDOT Certified Plant Technician representing the Producer signed the first Certificate of Compliance for each mix type, each day.
  • Perform all required sampling and testing in accordance with Schedule of Materials Control.
    • Perform air content and slump testing at the point of placement. 
    •  If testing is not possible at point of placement, correlation testing must be performed.
    •  If there is any question about the consistency or the quality of the concrete, run additional tests as necessary.
    • Notify Contractor and truck driver if air content or slump results are outside of Specifications.
  • Compressive Strength Testing (Cylinders):
    •  Check the Schedule of Materials Control for sampling rates.
    • When sampling for casting cylinders, sample at least 1 cubic foot of concrete and remix prior to casting cylinders
    • Initial cure cylinders in a moist curing environment (coolers) maintained at 60⁰ to 80⁰F for up to 48 hours.
    • After the initial cure, submerge in a curing tank maintained at 60⁰ to 80⁰ F for up to 7 days.
    • Provide protection from extreme variations in temperature from the time of casting cylinder until it is transported to the lab.
    • Use cylinder mold caps when delivering cylinders to the lab for further curing
  • Finishing:
    • Check allowable tolerances and review finishing procedures.
    • Check surfaces with straight edges for correct line and grade prior to initial set so that corrections are made while concrete is still workable.
    • Do not bless the surface with water.
  • Curing:
    • Review current curing requirements.
    • Verify an approved curing compound is used from the Approved/Qualified Products website.
    • Use an airless spraying machine for applying the curing compound with a re-circulating bypass system.
    • Check application rate of curing compound for uniformity, yield, and timely placement. (Typically white as a sheet of copy paper)
    • Ensure compliance with rain and cold weather protection requirements.  
  • Backfilling against concrete:
    • Review backfilling procedures and time lines for compliance with the specifications.
  • Maintain a daily plant diary:
    • Include hours of production, equipment, concrete temperatures, air content, slump reading, cylinder data, location of work, yield, weather, air temperatures, any instructions directed to Contractor, and problems or unique circumstances encountered.

References:   MnDOT Standard Specifications for Construction, Contract Plans and Special Provisions, Schedule of Materials Control and MnDOT Concrete Manual.