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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:
SP91-28
Date:
February 1, 1986
Author(s):
C. Andrade
Publication:
Symposium Papers
Volume:
91
Abstract:
The substitution in the concrete fabricated with ordinary portland cement by blended materials may affect the excellent protective properties of the concrete vis-a-vis the steel reinforcements. Although the blended materials produce the favourable effect of increasing the concrete impermeability and density, they decrease the alkalinity. In the present paper, the results of the addition in the mix of two ashes (with low and high calcium and sulfate content) to mortars and concrete, are presented. In order to evaluate the possible corrosion, the Polarization Resistance and the Impedance as techniques of measurement, have been used. The specimens were held about two months in a chamber with 90-100 % of relative humidity. The results show that the protective properties of the concrete vis-a-vis the steel bars are not altered by the blended materials, while may induce localized corrosion. in mortars some proportion of them
DOI:
10.14359/10090
SP91-33
Ravindra K. Dhir, Frederick H. Hubbard, John G. L. Munday, and M. Roderick Jones
The results of studies undertaken into the compositional and physical characteristics of a wide spectrum of UK fly ashes, and some from overseas, are examined in conjunction with data available from the literature. No direct relationship was found to exist between the compositional nature of a fly ash and its behaviour in concrete. The single most significant physical parameter characterising ash is shown to be fineness (as measured by 45 um sieve retention) and is used in developing two schemes classifying (a) the water-reducing and (b) the cement-saving abilities of an ash, which give a simple measure of ash suitability for use in concrete. It is demonstrated that for a correctly designed concrete, the grade of ash does not significantly affect its engineering properties, but only the cement savings that can be achieved.
10.14359/10093
SP91-30
P. K. Mehta
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.
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
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