Acceptance of fly ash or natural pozzolan will be on the basis of approved sources and upon satisfactory test results on samples obtained at the project site. Test results of fly ash or natural pozzolan shall meet the requirements of AASHTO M 295 and the Specifications of the Iowa Department of Transportation. Approval will require identification of the specific sources of the coal from which the ash is derived.


Approval is based upon fly ash produced when the power plant is utilizing specific materials, equipment, and processes. Any change in materials, equipment, and processes will void any source approval and require that a new approval be sought. Approved fly ash sources are listed in the Materials Approved Products Listing Enterprise (MAPLE).


Fly ash produced immediately prior to shut down and after start up may be quite different from the fly ash normally obtained. The fly ash can be affected to the point that it does not meet specifications. Monitor samples or verification samples tested by the Iowa Department of Transportation not meeting specifications will void the source approval.



A.   Certified Source


Approved certified sources of fly ash or natural pozzolan are listed in the Appendix A of this IM. A source may furnish fly ash or natural pozzolan on the basis of certification provided:


1.   The quality-monitoring program meets the minimum sampling and testing frequencies established in ASTM C 311. The tonnage units expressed therein are interpreted to refer to as-marketed material. The producer shall test at least one sample for each consecutive 30 days, for the months of March through October for conformance to Iowa Department of Transportation specifications. The test reports for all monitor samples shall be submitted to the Iowa Department of Transportation within 45 days of the sampling date.


In addition to the test frequencies established in ASTM C 311, daily control tests shall be made to establish the uniformity of the fly ash or natural pozzolan being produced. Specific tests shall be agreed to by the engineer and may vary from source to source. As a minimum, the loss on ignition and percent retained on the No. 325 mesh sieve shall be determined.


Sample test records and shipment reports shall be available for inspection by Iowa Department of Transportation personnel for at least three years after the fly ash or natural pozzolan has been tested.


The Quality Control Laboratory will be considered approved if it is properly equipped and staffed to perform the tests required for an accepted Quality Control Program. Continued approval of the control laboratory will depend on the comparison of its test results with the Iowa Department of Transportation Central Laboratory. If major differences are found, an attempt to resolve them shall be made as quickly as possible. Continued unresolved differences in test results will be considered a basis for discontinuing control laboratory approval.


2.   The fly ash shall comply with AASHTO M 295, either Class F or Class C, except the value of total equivalent alkalies (expressed as Na2Oe) shall not exceed 3.80%.


3.   Natural pozzolans shall comply with AASHTO M 295. In addition, manufacturer shall submit to the Office of Construction and Materials, test results of two Iowa DOT Concrete Mix Designation C-3WR-C20, or C-4WR-C20, concrete mixtures, one as a control and one with the natural pozzolan at a replacement rate recommended by the manufacturer. The coarse aggregate used shall be an Iowa DOT approved limestone or dolomite. Fly ash, sand, air entraining agent and chemical admixtures used shall also be from Iowa DOT approval lists. The air content shall be in the range of 5.5% and 7.0%.


      The tests and approval requirements are listed below:


·        ASTM C39, Compressive Strength at 7, 28, and 56 Days: 90% or better of control.

·        ASTM C78 or C293, Flexural Strength, at 28 Days: 95% or better of control

·        ASTM C157, Concrete Shrinkage up to 56 Days: 95% or better of control or 56-day shrinkage less than 0.040%.

·        ASTM C666, Freeze-Thaw Resistance up to 300 Cycles: 95% or better of control or a durability factor greater than 90%.

·        ASTM C1202, Rapid Chloride Permeability, 50% or lower of control.


4.  The fly ash or natural pozzolan has shown conformance to the applicable specifications for a continuous period of at least the last six months.


5.   Each shipment of fly ash or natural pozzolan is properly certified.


The supplier of certified fly ash or natural pozzolan shall furnish for the project records two invoices or bill of lading copies that bear the following certification statement and the signature of a responsible company representative:


Certification Statement

The material herein described has been sampled and tested as prescribed by the Highway Division of the Iowa Department of Transportation and complies with the applicable specification requirements for Class _____ fly ash/pozzolan.






The bills of lading or invoices shall include project number, if available, source name, source location, source code, class, and quantity in the shipment.


These copies of the bill of lading or invoice shall accompany each load, and shall be retained at the project or ready mix plant for the Project Engineer records.


The truck tanker shall have a copy of the invoice or bill of lading attached directly to the tanker portion of the truck. When the tanker unloads the contents at the project site, the unloading time and material final destination (storage "pig" number) shall be marked on this copy and left with the invoice or bill of lading copies.


In the case of more than one project being supplied by a ready mix plant, the plant shall furnish the Project Engineer, for each project, either a copy of each bill of lading or invoice, or a listing of the bills of lading or invoices representing the fly ash or natural pozzolan incorporated in the project. This listing shall bear the signature of a responsible supplier representative.


The source, car or truck number, ticket number, ash type, and quantity of each shipment of fly ash or natural pozzolan used on a project shall be recorded on Form #830211, or Form #830224, whichever is applicable.


6.   At least one monitor sample shall be secured annually from power plant sites, located in Iowa or within 50 miles from Iowa borders, and be tested by the Iowa Department of Transportation. The test results of monitor samples shall be in compliance with current specifications.


7.   Co-Mingling of Fly Ash


Mixing of fly ash from different sources, different generating plants/units, or different classes into one storage bin or silo will not be allowed, with the following exception.


When the same coal stockpile, the same brand and model of generating equipment, the same process of operation, and the same brand and model of fly ash collection equipment are used; fly ashes from different units at a generating plant may be considered for approval as a single blend and stored in a silo. To apply for the approval, the producer or marketer shall provide the composite sample test data (composite samples should represent 3200 ton increments of fly ash collection or the month whichever comes first) from the separate units for the  previous 12 months. The Office of Materials will conduct a statistical t-test to compare major physical and chemical properties of the two fly ash sources. If the t-test results show the test data means to be equal at a significance level of 0.05, the blending process may be allowed. Annual analysis may be required for continued approval. Blending will only be allowed within the storage silo.


At ready mixed concrete plants and paving batch plants, a fly ash storage bin shall be emptied, as far as practical, prior to refilling from a different source.


B.   Sources for Pavement Undersealing and Jacking


1.   Class C Fly ash listed in the Appendix A may be used for pavement undersealing and jacking, provided that it meets the setting time criterion given below.


2.   A mixture of 3 parts fly ash and 1 part Portland cement shall have an initial setting time between 30 minutes and 3.0 hours. Initial set is defined as 100-psi resistance when measured in accordance with ASTM C 403.



Required verification samples will be secured at the project site just before incorporation into the work. Test results, which do not comply with the specifications, may be considered sufficient cause to rescind approval to furnish fly ash or natural pozzolan on certification basis. Construction, which contains fly ash or natural pozzolan represented by verification samples, which show deficient test results, will be subject to the requirements of Article 1105.04 of the Standard Specifications.


Depending upon certain chemical characteristics, fly ash is marketed as either Class F or Class C ash, or Class N for natural pozzolans, per AASHTO M 295. The identification submitted with the verification samples sent to the Central Laboratory should include the normal descriptive information as well as the source of the ash, the marketer and the class of the ash.


Precautionary measures shall be taken to prevent cement contamination of fly ash or natural pozzolan samples obtained at the proportioning plants. The samples shall be taken preferably as follows:


1.   Directly from the delivery transport vehicles


2.   Drop a sufficient amount of material in a clean container or a clean end loader bucket, and obtain a representative sample.



For checking the AASHTO M 295 uniformity requirement, the average density for a source will be computed based on the values tested and reported by the Central Materials Laboratory. The value of average density will be updated if it is more than 0.10 gram/cm3 different than the current value listed in the Appendix A. The density update will generally be done in the October IM revision unless a change in fly ash operation or coal source occurs.