With otherwise similar chemical end mineralogical composition of fly ash, is it its fineness which has the most significant influence on the properties of concrete. Coarser fly ash is, as a rule, suitable only as a substitute of s portion of fine aggregates or as s correction of unsuitable shape and
Influence of fly ash characteristics on the strength of portland-fly ash mixtures
β Scribed by P.K. Mehta
- Publisher
- Elsevier Science
- Year
- 1985
- Tongue
- English
- Weight
- 904 KB
- Volume
- 15
- Category
- Article
- ISSN
- 0008-8846
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β¦ Synopsis
Modern thermal power plants are producing large amounts of fly ash that is generally quite suitable for use as a supplementary cementitious material in concrete. However, for tilis purpose the fly ash utilization in the United States continues to remain low, mainly on account of lack of quality control. This is because the current standards on fly ash do not contain specifications and test methods that are able to assess adequately the performance of a fly ash in concrete. Based on tests on II different fly ashes and direct determination of compressive strength of test mortars made with a fixed proportion of fly ash by weight of the cementitious material, and a fixed ratio between water and the cementitious material, it seems that the calcium content and particle size distribution of the fly ash are the most important parameters governing the strength development rate in normally cured portland cementfly ash mixtures.
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The effect of replacing 30 % of portland cement by Spanish fly ash (class F according to ASTM C-618) and their sized fractions obtained using sieves on compressive and flexural strength of mortars was investigated. The study reveals an enhancement of compressive strength when fineness of fly ash fra
The strength of concrete at early ages has assumed a co~iderable significance in recent years due to the several specific requirements ot the modern construction industry, like the early striking or forms, early transfer of prestress etc. However, fly ash concretes are known to-have a lower early ag
The effects of two super water-reducing admixtures on the compressive strengths and elastic moduli of portland cement mortars containing fly ash were determined. The results show that the effectiveness of the chemicals for improving the strengths of mixtures in which portland cement is partially re
Five fly ash concretes were found to gain considerable strength beyond 28 days when standard cured in water at 20Β°C. However, strength development came to an almost complete stop after 3Β½ years, at what time the fly ash activity factors with respect to concrete compressive strength ranged from 0.86