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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:
SP91-77
Date:
February 1, 1986
Author(s):
H. L. Isabelle
Publication:
Symposium Papers
Volume:
91
Abstract:
Silica fume has been used commercially for five years in Canada, particularly in the province of Quebec where most of the material is produced. Field problems such as plastic shrinkage that were experienced in the early stages and the distinct nature of this pozzolan caused some concern among prospective users who, while recognizing the unique properties and potential of silica fume, were hesitant to specify it. Added to their apprehension was the unavailability of a recognized standard. These considerations prompted the Concrete Materials and Construction Committee of the Canadian Standards Association (CSA) to develop a specification for silica fume. Findings from research by the University of Sherbrooke, Quebec, and the Canadian Center for Mineral and Energy Technology, Ottawa, Canada, provided input for the new specification which is now part of CSA Standard A23.5, Supplementary Cementing Materials and Guidelines for their Use in Concrete. During the preparation of the specification, close contact was maintained with Committee 226 and ASTM Committee C618 which are in the process of preparing a state-of-the-art report and a specification, respectively. The Canadian specification, believed to be the first of its kind in the world, will eventually be updated particularly as regards to the ASTM C 311 methods of tests which were originally developed for pozzolans that are not as finely divided as silica fume.
DOI:
10.14359/1783
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
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
SP91-24
Shigeyoshi Nagataki, Hiroyuki Ohga, and Eun Kyum Kim
This paper reports the long term results of experiments carried out since 1969 to investigate the carbonation phenomena in concrete with and without fly ash. They were carried out for different mix proportions by varying cement factor, replacement ratio of fly ash and water-cement ratio. The specimens were cured indoors and outdoors after water curing for periods of 1, 7, 28 and 91 days. It was found that the carbonation and the corrosion is considerably affected by mix proportions, initial curing period in water and exposure conditions. Depths of the carbonation of concrete cured indoors increase with age, short initial curing period in water and high water-cement ratio. Corrosion of reinforcing bar embeded occurred due to the carbonation.
10.14359/10086
SP91-25
A. M. Paillere, M. Raverdy, and G. Grimaldi
Carbonation of concrete is increased in the presence of a high percentage of granulated blast-furnace slag in the cement and is also enhanced after subjecting concrete to freezing and thawing cycles. Air entraining agents do not modify the carbonation when the concrete containing portland or cements with low-calcium fly ash and granulated blast-furnace slag (< 20 X) is subjected to freese-thaw cycles. Carbonation is increased in the cement containing 84 % of slag. Uncarbonated concrete resists freezing and thawing better than that carbonated previously.
10.14359/10087
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