Proposed Revisions to Specifications and Test Methods for Use of Fly Ash in Portland Cement Concrete

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Title: Proposed Revisions to Specifications and Test Methods for Use of Fly Ash in Portland Cement Concrete

Author(s): Oscar E. Manz

Publication: Special Publication

Volume: 91

Issue:

Appears on pages(s): 659-680

Keywords: concretes; fineness; fly ash; free lime; performance; pozzolans; setting (hardening); specifications; General

Date: 2/1/1986

Abstract:
Many of the current standards for fly ash to be used in portland cement suffer from prescriptive requirements not necessarily related to the material's performance in concrete. The development of performance specifications is being encouraged, and classifying fly ash by reference to type of coal is being questioned. To use fly ash as a mineral admixture, the potential strength contribution to a reference mortar seems to be the most important consideration. To overcome the inconsistency with cement in the ASTM C 311 pozzolanic activity index, many countries have revised the test by incorporating fixed fly ash/cement ratio by weight, fixed water/cement + ash ratio, and accelerated curing at various temperatures for up to 7, rather than 28, days. Various studies to improve pozzolanic test methods are summarized, and recommendations made to simplify present fly ash standards, and to change their orientation from prescriptive to performance.