The provisions of this IM shall apply to the, fabrication of precast concrete units. Precast concrete units shall be produced in a plant which is approved by the Construction and Materials Bureau. The requirements are listed in Sections 2416, 2419, 4145 and 4149 of the Standard Specifications. Requirements for specific precast units are found in the following IMs:
445.01 - Concrete Pipe & Special Sections
445.02 - Precast Box Culverts
445.03 – Mechanically-Stabilized Earth (MSE) Wall Panels
445.04 - Concrete Segmental Modular Blocks, Dry Cast
445.05 - Concrete Segmental Modular Blocks, Wet Cast
445.06 – Precast Concrete Noise Walls
571- Precast Concrete Barrier
PLANT APPROVAL
Approval of precast concrete plants shall be based on the following:
Receipt of a written request for approval of a precast concrete plant for specific precast products. The request shall be submitted by the fabricator to the Construction and Materials Bureau.
Satisfactory inspection of the plant by both the District Materials Engineer and the Prestressed and Precast Concrete Engineer.
A plant Quality Control Plan approved by the Construction and Materials Bureau.
A recommendation for approval by the District Materials Engineer.
Each Approved Precast Concrete plant shall submit an updated quality control plan to the Prestressed and Precast Engineer by the end of every even calendar year. Precast plants failing to furnish an updated quality control plan by January 31st will be removed from the approved list.
A Quality Control Plan shall be developed for each individual plant in accord with applicable portions of IM 445, Appendix C
Noncompliance to the approved Quality Control Plan shall constitute grounds for the producer to be placed on conditional status by the District Materials Engineer. The conditional status requires the producer to contract with a consultant inspection firm to inspect the producer’s entire product for a period of 90 days, to allow the producer to revise the QC production operations so to be able to remove the conditional status. Continued noncompliance shall be considered sufficient grounds to remove the producer from the Approved Producer List.
MATERIALS
All aggregates, cements, admixtures, and reinforcing steel shall comply with Sections 2416, and 2419 of the Standard Specifications. Only materials from approved sources, shall be used. Sources of materials shall be indicated in the Quality Control Plan. The District Materials Engineer shall be notified if a source of material shall be changed.
Only preapproved mixes shall be used in the casting of concrete. Any alteration or change made to the approved mix shall require new mix approval.
For aesthetic concrete cast with form liners or rustication, use crushed stone coarse aggregate. This includes MSE and noise walls. Use crushed stone coarse aggregate for concrete receiving color sealer or texture treatments and precast box culverts for bikeways and pedestrian traffic.
Blending of aggregates from different sources at the precast plant may be allowed if the individual aggregates are geologically similar and meet the applicable quality requirements, if approved by the District Materials Engineer.
Failing test results on monitor samples may result in rejection of all fabricated precast items in stock and revocation of plant approval.
FACILITIES & EQUIPMENT
Facilities and equipment for materials handling and storage, proportioning, weighing, mixing, cutting, welding, and placement of reinforcement steel, curing, and pipe testing shall comply with the applicable requirements of Sections 2419, and 4145 of the Standard Specifications.
Concrete batching equipment and testing equipment shall be calibrated according to the approved Quality Control Plan. (Once per year, or as often as deemed necessary by the DME.)
NOTE: If a ready mix plant supplies concrete, then the plant shall be calibrated and approved by the District Materials Engineer.
PRODUCTION
The producer shall notify the DME prior to the start and end of seasonal production and at least 48 hours prior to starting project specific production.
For all production, the producer plan shall indicate the quality control inspection procedure to be used in the manufacture of the product, including:
a. Reinforcing steel fabrication and placement
b. Concrete mix design and proportioning
c. Concrete placement and consolidation
d. Concrete curing
Cold weather procedures shall meet the requirements of Article 2403.03F of the Standard Specifications.
Precast items shall not be moved until the designated moving strength is obtained. If no moving strength is specified, then the producer shall submit lifting details for review and determination of an accepted moving strength.
Precast products can’t be shipped until the products are minimum 3 days old and attain 28 day strength.
TESTING
Process Control testing shall be performed by the producer. The methods and rates shall be indicated in the Quality Control Plan and shall meet the applicable requirements. identified in the IM for the specific precast concrete product.
QUALITY CONTROL TECHNICIANS
The Quality Control Technician shall be appointed fulltime by the producer to be responsible for the quality control process and testing at each plant. The Quality Control Technician shall:
a. Possess knowledge of the plans, shop drawings, and specification requirements.
b. Possess knowledge of the product manufacturing operations and processes.
c. Possess a valid IDOT Level 1 PCC Certification or ACI Level I Certification when casting operations require physical testing such as air entrainment or slump testing, and making, curing and testing compressive strength specimens, etc.
d. For dry cast modular block production, the requirement of Level I PCC Certification or ACI Level I Certification may be waived if the District Materials Engineer recommends that the QC technician has adequate knowledge about dry or wet cast concrete production.
e. Be responsible and have the authority to correct and/or stop any operation that is found to be causing non-conforming attributes, and to reject all products not meeting Iowa DOT requirements.
RECORDS
For iron and steel materials, the producer shall retain all required documentation for a minimum of seven years from the time the products are shipped for incorporation into a project in accord with Materials IM 107.
All other reports and material certifications shall retain at the production plant for one-year after the products are shipped for incorporation into the project.
A copy of all reports of approved/certified materials (aggregate and cement certifications, Mill Test Reports for steel reinforcement, etc.) shall be kept on file at the fabrication plant for one year after project completion and Records shall be available at any time for review by the District Materials Engineer or his representative.
Records shall include, but not be limited to:
a. Test results performed during fabrication and on finished products, such as:
1) Concrete cylinder or core strengths
2) Load bearing tests
3) Entrained air content
4) Slump tests
5) Concrete absorption tests
b. Records of manufactured products by:
1) Manufacture date
2) Size
3) Class
4) Quantity
c. Equipment calibration reports shall be kept for a minimum of one year.
STOCKPILES
The producer shall keep noncompliant or otherwise deficient products separated from the stock that may be shipped and/or incorporated into a project under the certification program.
Aggregate for precast products must have samples for quality testing secured or witnessed by Agency Personnel at a minimum frequency of one per year.
The District Materials Engineer shall be responsible for establishing and performing the monitor sampling and testing program for each plant. Noncompliant test results shall be considered sufficient cause for rejection of the lot represented and may be considered sufficient cause to rescind approval to furnish products on a certification basis. The District Materials Engineer reserves the right to change monitor-sampling rates.
CERTIFICATION DOCUMENTS
The producer of certified concrete pipe, special sections, or other precast units shall furnish, on each shipment day, a certified bill of materials or invoice which identifies the county, project number, contractor, and number of pieces of each class, size, and length and the plant the precast unit was fabricated.
Certification of compliance shall include a statement indicating materials in shipment are certified to be in compliance with:
Applicable Iowa DOT IMs, Standard Plans, and Specifications
Applicable AASHTO and/or ASTM requirements
All Buy America Group 2 requirements as described in IM 107.
The statement shall be signed by a designated, responsible company representative.
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One copy of the above-described document shall be forwarded to the Project Engineer on the day the item is delivered to the project.
The fabricator shall also provide summary quantity documentation, as shown in Appendix B, to the District Materials Office responsible for the project and the project engineer at the completion of the shipments to the project. A designated representative shall sign the certification statement on the summary documentation.
Units certified and properly marked as per applicable IMs (i.e., 445.01, 445.02, 445.03, 445.04, 445.05, 445.06, 571) may be incorporated into the project. Each shipment should be inspected for damage at the project site due to handling and shipment. Damaged units shall be rejected. Each shipment to Iowa DOT projects shall be accompanied with proper certifications.