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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:
SP91-26
Date:
February 1, 1986
Author(s):
N. Saeki, Y. Fujita, and N. Takada
Publication:
Symposium Papers
Volume:
91
Abstract:
The properties of the surface layer of concrete may be closely related to the causes of scaling and play an important role in the durability of concrete. In order to obtain the mechanical properties of the surface layer, which are affected by the type of cements, curing and atmospheric condition etc., some tests were carried out by using model specimens with penny shaped cracks (penny shaped crack test) or truncated steel core (pull out test). The ratio of the surface layer strength to split tensile strength was found to be approximately proportional to the thickness of the layer. The surface layer strength is influenced by the curing conditions and is related to the degree of scaling and frost damage.
DOI:
10.14359/10088
SP91-27
Inger Meland
This report presents results from an investigation where fly ash has been used in cement to try to reduce an observed alkali-silica reactivity in tile covered mortar and concrete constructions such as swimming pools and larger shower cabinets. Examinations of ceramic tiles showed that soluble silica formed when the material was exposed to sodium hydroxide solution. For testing according to ASTM C227-81 "Potential Alkali Reactivity of Cement-Aggregate Combinations (Mortar-Bar Method)" concrete prisms were moulded using ordinary Portland cement or fly-ash cement with crushed ceramic tiles as aggregate. All the prisms showed changes in length; however, the changes are less in prisms made with fly-ash in cement. From these observations it seems that it is possible to reduce the damage caused by alkali-silica reactions in such structures by use of fly-ash in cement. Long term tests are being done on tile covered concrete slabs.
10.14359/10089
SP91-28
C. Andrade
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
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
SP91-34
R. A. Helmuth
Specifications for fly ashes should be based on a proper understanding of the factors controlling, and test methods for, water requirements for flow. The reduction of the water requirement for flow of concretes which results from partial replacement of portland cements by certain fly ashes is commonly attri-buted to the spherical shape of many of the fly ash particles. Critical re-examination of the literature does not support that conclusion. An alternative hypothesis is proposed: the water reduction is a result of adsorption of very fine fly ash particles on portions of the cement particle surfaces, with result-ing dispersion of the cement particles, similar to the action of organic water-reducing admixtures. This hypothesis is consistent with published data on fly ash-cement-admixture interactions. This effect should be separated in the test methods and specifications from that of the amount of fly ash coarser than 45 um, but is not in the present ASTM C 311 test for water requirement.
10.14359/10094
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