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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 30 Abstracts search results
Document:
SP202-22
Date:
August 1, 2001
Author(s):
J. Asselanis and P. K. Mehta
Publication:
Symposium Papers
Volume:
202
Abstract:
A petrographic examination on a companion test slab that was cast and cured under the same conditions as a massive raft foundation was performed to gain insight into the observed crack-free nature of the concrete. The foundation was made of a high-volume fly ash concrete mixture designed to last a thousand years. The absence of cracking is attributed to a homogenous microstructure of the high-volume fly ash system and close attention to the selection of concrete materials, mixture proportioning, and curing.
DOI:
10.14359/10793
SP202-23
D. D. Bui and P. Stroeven
Fly ash is increasingly used on a worldwide scale in cement and concrete because of reduced cost, material and energy savings, and improved resistance and durability of the fly ash concrete. One of the drawbacks of (Class F) fy ash concrete is its potentially relatively low early strength. Highly reactive pozzolanas such as silica fume and metakaolin can be used to enhance the properties of fly ash concrete. However, silica fume and metakaolin are relatively scarce and expensive. Rice husk ash is an active pozzolana produced by controlled burning of rice husks, hitherto an agricultural waste. This paper describes the combined use of rice husk ash (RHA) and fly ash in high-perfomrance concrete. The high-performance concrete was based on a gap-graded concrete aggregate with fine sand. Further, a superplasticizer was applied. These ternary blended cement concretes showed greater strength gain than the fly ash concrete.
10.14359/10794
SP202-24
A. A. Azevedo, M. 1. C. Martins, and D. C. Dal Molin
A large number of relatively new reinforced concrete structures may require intervention due to problems affecting their durability. Repair and replacement costs of structures account for a considerable share of the total cost of constructions. Rice-husk ash (RHA) concrete displays lower permeability due to changes in the concrete microstructure, which reduces the vulnerability of this material to the action of aggressive agents. This study assesses concrete durability properties to chloride ions, an aggressive agent. The effect of chloride ions was investigated with tests of compressive strength and chloride penetration. These tests were performed in high initial strength portland cement concrete (CPV-ARI) modified with the addition of rice-husk ash (RHA) and in pozzolanic portland cement concrete (CPIV). The input variables were the water/cimentitious ratio (0.30-0.35-0.45-0.60-0.80) and the contents of the rice-husk ash additions (0%-5%-lo%-IS%/,-20%). Results show that the addition cf rice-husk ash to CPV-ARI concrete had no significant effect on compressive strength properties when compared to the reference concrete. Results for chloride penetration show that the addition of RHA produces an average reduction of 126.6% on the charge passed. Comparative results of RHA CPV-AR1 concrete and CPIV concrete show that the compressive strength performance of the latter is poorer than the former. Chloride penetration results show that CPIV concretes displayed a better performance than CPV-ARI concretes with and without the addition of RHA.
10.14359/10795
SP202-25
W. J. McCarter, G. Starrs, and T. M. Chrisp
This paper utilizes electrical methods to follow the early hydration characteristics of a range of materials activated with calcium hydroxide at room temperature (20°C). The electrical response is measured in terms of the in-phase (i.e. resistance) and quadrature (i.e. capacitance) components of the sample admittance. A number of presentation formalisms are exploited in identifying the stages of hydration and studying reaction kinetics in alkali-activated systems. It is also shown that the electrical response of the material displays a frequency dependence, which is particularly evident in the measured capacitance. The work highlights the applicability of the electrical method as a non-invasive, non-destructive technique in evaluating the reactivity of supplementary materials.
10.14359/10796
SP202-26
W. Roszczynialski, W. Noch-Wczelik, and M. Gawlicki
Fluidized bed coal combustion produces a new kind of fly ash by-product. Fluidized bed fly ashes have different chemical composition and physical properties than conventional fly ashes. They can be used as complex addition to cement where they play simultaneously the role of sulphate setting time controlling agent and high active pozzolanic admixture as well. This gives the possibility to reduce the consumption of portland cement clinker and gypsum. Thus, it may also contribute to the reduction of CO, emission. In the paper the results of the laboratory investigations of fluidized bed fly ashes as cement additive and the effects of their industrial implementation will be presented.
10.14359/10797
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