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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 78 Abstracts search results
Document:
SP91-30
Date:
February 1, 1986
Author(s):
P. K. Mehta
Publication:
Symposium Papers
Volume:
91
Abstract:
Concern is growing that prescriptive and separate standards are an obstacle to widely using such by-product mineral admixtures as fly ash, granulated slag, and condensed silica fume. Since natural as well as by-product pozzolanic and cementitious admixtures offer similar technical benefits when used in concrete, it is desirable to develop a single performance-oriented standard. With this objective, the principal chemical and physical requirements of a few selected standards are reviewed, with a focus on fly ash and its relevance to current materials. A rational approach is suggested and specific recommendations made toward developing a performance standard to cover all mineral admixtures.
DOI:
10.14359/1778
SP91-31
Oscar E. Manz
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.
10.14359/1779
SP91-32
P. F. Walsh
In drafting the durability section of the Australian concrete code, the committee faced both an urgent problem and a lack of precise data. This paper outlines the concepts in the draft code with a particular emphasis on the protection of reinforcement and the influence of fly ash on durability. Based on a qualitative understanding of the fundamental parameters, some engineering decisions and classifications are made. Where ample curing or self-curing is available, fly ash is a desirable component of durable reinforced concrete. For building exteriors where minimal curing is provided, achieving quality concrete cover is difficult. In this respect, concrete containing fly ash may be more affected than plain concrete.
10.14359/1780
SP91-56
F. F. Radjy, T. Bogen, E. J. Sellevold, and K. E. Loeland
Extensive technical work has established that high-performance concrete and cementitious materials can be proportioned practically and economically by using condensed silica fume additives. These hybrid chemical/mineral admixtures can be used for applications ranging from bridge overlays, concrete roof tiles, and fiber reinforced cements to structural uses, both on land and offshore. First significant applications began some ten years ago in Norway, with cement replacement as the main benefit. While cement replacement still continues as the main end use in the Scandinavian markets, performance enhancement of cementitious and concrete applications is the dominant attraction for users outside of Scandinavia. After a brief consideration of the history, a range of durability and high-strength applications are reviewed. It is shown that this range of varied applications is generally driven by particular features of performance enhancement.
10.14359/1781
SP91-78
Ken Newman
This paper examines recent trends in European and British cement and concrete standards, concerning the production and use of blended cements and concrete mixer combinations of cements and additions, such as slag and pulverized fuel ash. The implications of the new categorization of six types of cement, changes in the definition of "cement," and acceptance of equivalence of performance in terms of concrete strength grade, are discussed. The principles being adopted in the UK for the approval of the use of additions in concrete include the adoption of the standard for blended cement as the basis, recognition of the cementitious properties of standardized additions and certification procedures for confirming compliance of concrete mixer blends with the standards of blended cements. Provided these procedures are followed, the answer to the question--blended cements or concrete mixer blends?--lies in a clearer definition of responsibility for their fitness for purpose, the relative costs of using blended cements or concrete mixer blends, and the local market demands.
10.14359/1791
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