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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:
SP91-78
Date:
February 1, 1986
Author(s):
Ken Newman
Publication:
Symposium Papers
Volume:
91
Abstract:
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.
DOI:
10.14359/1791
SP91
Editor: V.M. Malhotra
SP91 This contains 78 symposium papers, bringing together the expertise of representatives from industry, government and universities. These volumes present the latest advances in the use of fly ash, silica fume, slag and natural pozzolans in concrete. New technologies are explored to provide ways in which these valuable mineral by-products can best be used to conserve both resources and energy. Case studies include: the effect of fly ash on physical properties of concrete; evaluation of kiln dust in concrete; effect of condensed silica fume on the strength development of concrete, and the influence of slag cement on the water sorptivity of concrete.
10.14359/14048
SP91-16
Oscar E. Manz and Gregory J. McCarthy
Western U.S. lignite and subbituminous fly ashes have higher CaO + MgO + SO3 and lower Al203 + SiO2 than bituminous ashes. They also have lower loss on ignition and greater proportions of crystalline material. No more than one-third of the total lime is free lime. Several chemically, physically, and mineralogically different lignite and subbituminous fly ashes were used in varying substitutions for portland cement. The following data were obtained: compressive strength, effect of admixtures, freeze-thaw durability, and resistance to sulfate solutions. Depending on the mix proportions, a high lime fly ash may not contribute more to compressive strength than one that has 50 per-cent less lime, and is coarser. High lime fly ashes produce excellent freeze-thaw durability. With certain high lime fly ashes, similar strengths are obtained by either 25 or 75 percent substitution for cement. Extremely low expansions of several high lime fly ash concrete specimens soaking in 10 percent Na2S04 for up to 3 years have indicated that the R factor, (CaO-5)/Fe203, for sulfate resistance is not totally valid. Concretes using high lime fly ashes produce higher early strengths than low lime bituminous ashes.
10.14359/10078
SP91-17
J. Papayianni
Lignite Fly Ash (LFA) was used in concrete replacing Portland cement at 0, 30, 40, 50, 60, 70, 80, 9 0 and 100%. Properties investigated in concrete prepared with different percentages of LFA were: 1. Compressive and flexural strengths (7, 28 days 3, 6 months 1, 2, 3, 4 and 8 years). Water to cement plus LFA ratios (W/C+F) 0.55, 0.65, 0.75,0.85, 0.95. Concrete slump 40-50mm, 60-70mm, 80-100mm, lOO-150mm, 150-200mm. A total of 10,000 specimens were tested for compressive strength at various ages during 5 years. 2. Modulus of elasticity according to ASTM C469-65. 3. Bond between steel-concrete according to ASTM C234-71. The test data showed that LFA can replace Portland cement when used as a separate batch material up to 40% in reinforced concrete and up to 70% in plain concrete.
10.14359/10079
SP91-18
Shui Cuijuan, Gong Luoshu, and Wang Haimin
Fly ash in China contains low CaO (5%) and is obtained by burning bituminous coal. Thus such a fly ash concrete exhibits low early strength at an optimal dosage of 10-20%. Two methods were adopted to increase the dosage of fly ash (1) introducing calcium directly during burning or (2) as an additive. The effect of dosage of such fly ash on strength, shrinkage, frost resistance, carbonation and steel corrosion of concrete was investigated. Method 1 is effective in improving the activity of fly ash and permits the optimal dosage of fly ash to increase by 30-4O%. Early strength of concrete is also increased. Method 2 is applicable to steam-cured fly ash concrete at a high dosage (5O-60%). X-ray diffraction analysis was used to study the process of reaction between fly ash and cement.
10.14359/10080
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