The American Society for Testing and Materials (ASTM) committees for cement, SCM's and concrete currently has a host of issues open for ballot. Our colleagues at the American Coal Ash Association (ACAA) have shared some key issues that their Technical Committee have been evaluating. The ADAA is highly thankful of the ACAA for sharing these developments allowing the international community to stay abreast of these global developments.
ASTM Committee C09 on Concrete and Concrete Aggregates has two of the items affect fly ash:
- Item 10 has been balloted several times previously. It proposes a change to allow the use of up to 4g of a sample for the LOI test instead of 1g as the standard currently reads. In this ballot, some language that some committee members found confusing was clarified.
- Item 11 recently passed Subcommittee C09.26 on Chemical Reactions. The rationale for the ballot is: “For ease of use, the several locations in C441 which refer to C227 are proposed to be revised to include the relevant text from C227. This will facilitate the use of C441 as users will not need to refer to procedures in C227 within C441.” In other words, there are no changes in the procedure itself.
ASTM Subcommittee C09.48 on Performance of Cementitious Materials and Admixture Combinations is balloting a new “Standard Method of Test for Determination of the Foam Index of a Cementitious Mixture.” Foam index is the most widely used (unstandardized) test to determine the impact that fly ash containing native and activated carbon has on air-entrained concrete. The test is typically run on-site to help marketers decide whether fly ash can be sold or not. Although standardising the foam index can be positive for the industry, the Technical Committee noted that the proposed standard was developed with no input from fly ash marketers or other stakeholders.
ASTM Subcommittee C09.24 on Supplementary Cementitious Materials is balloting four items:
- Item 1 is the new “Standard Specification for Ground Glass Pozzolan Use in Concrete.” The Technical Committee asks members to review the proposed specification to ensure a fair technical comparison with other pozzolans.
- Item 2 is a change to how the fly ash Strength Activity Index (SAI) is performed under standard C311. The change consists of using a 20 percent volumetric replacement of cement by fly ash instead of a 20 percent mass replacement (as the standard currently reads). The change also includes the use of a constant amount of water for the cement control as well as in the test samples containing fly ash, instead of a constant flow as the test currently states. Headwaters compared the proposed SAI to the current SAI using 10 different fly ashes and found that the proposed test method would yield results averaging 5 percent lower than the current SAI. The proposed use of a constant amount of water in lieu of the current constant flow nullifies the water reduction benefit of fly ash. ACAA’s Technical Committee recommends members vote negative on this item.
- Item 3 proposes removing the definition of fly ash in standard C618 and instead refer readers to C125 “Standard Terminology Relating to Concrete and Concrete Aggregates.” Although there are no differences between the fly ash definition currently in C618 and that in C125, the Technical Committee recommends members join subcommittee C09.91 on Terminology to contribute to the upkeep of definitions relevant to the industry.
Item 4 is the second iteration of a proposed change to standard C618 to use calcium oxide instead of the sum of silica, alumina and iron oxide to categorise fly ash. Fly ash with less than 18 percent CaO would be categorised as Class F and more than 18 percent would be categorised as a Class C. The main change on this second iteration is the addition of a note that allows the use of the CaO running average of the last three test samples. ACAA’s Technical Committee recommends support for this item.