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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 62 Abstracts search results
Document:
SP179-49
Date:
June 1, 1998
Author(s):
M. Eto, K. Maruyama and S. Ono
Publication:
Symposium Papers
Volume:
179
Abstract:
The authors have proposed a partially pre-cooling system for massive structures, such as gravity concrete dams. It is discussed in this paper how the effectiveness of the proposed method is discussed using the finite element analysis. In the ordinary pre-cooling system, pre-cooled concrete is placed in the entire region (width and depth) of a massive structure. In the proposed system , pre-cooled concrete is placed only in the surface layer. In order to evaluate the effectiveness of this system, a thermal stress analysis was conducted by the finite element method. The key parameters were the dimensions of the cooling system and cooling temperatures. The results show that the proposed system is rather effective than the conventional cooling system in terms of the thermal stress condition of massive concrete structures. In addition, the cost benefit is adequately expected.
DOI:
10.14359/10135
SP179-32
S. Nagataki, T. Kamada and A. Matsumoto
In this paper, a method to evaluate the crack size of concrete structures by infrared thermography was investigated. This method is based on the relation between the crack depth or width and thermal distribution in concrete. First, the influence of crack depth and width to thermal distribution was examined. Next, the influence of the distance between cracks and heater to thermal distribution was investigated. The effectiveness of this method was confirmed by the results of the experiment on flexural cracks in reinforced concrete beams. From these results, it was demonstrated that the thermal distribution measured at the surface of concrete by infrared thermography was effective in evaluating the crack size in concrete structures.
10.14359/6059
SP179-33
T. Katayama
Thin-section petrography, coupled with quantitative electron-probe microanalysis, is very useful in identifying reactive constituents and alkali-aggregate reaction in concretes, as well as in characterizing the nature of cement constituents, reaction products and gel products in old deteriorated concretes. EPMA analysis made it possible to detect chemical compositions of the unhydrated cement phases alite, belite, tricalcium aluminate, and the ferrite phase in the original cement used in old structures from Canada and Japan, made even 100 years ago. Coupled with detailed petrography in thin section, this technique also enabled us to estimate the thermal histories and composition of cement clinkers in hardened concretes, variations of CSH gels which reflect the degree of cement hydration, leaching and weathering of concretes, as well as the process of migration and alteration of ASR gels in concretes. The results thus obtained can be used for the assessment of cement properties and the durability of old concretes.
10.14359/6060
SP179-34
L . D’Aloia and G. Chanvillard
The N method of equivalent age )) is one of the currently used non-destructive testing methods of concrete strength estimation. It is based on the Arrhenius’ law, which has shown itself to be the most accurate in order to describe the influence of temperature on concrete strength development at early ages. A proper estimation is directly related to a correct determination of the Apparent Activation Energy : Ea. This is the unique parameter which characterizes the concrete mixture and which can be found in the Arrhenius’ law. The major aim of this paper is to show how calorimetric tests under semi-adiabatic conditions can be an alternative to unwieldy compressive tests procedures in order to determine Ea. The validity of the obtained Ea values has been verified by means of several mechanical tests. Moreover, the possibility of using either mortar or concrete is partially dealt with. The water to cement ratio appears to naturally be considered as a constant in proportioning an equivalent mortar. Finally, the evolution of the Apparent Activation Energy in relation to the degree of hydration is given. Hence, the widespread opinion that Ea depends on the degree of hydration is confirmed and a field of definition can be brought to the fore.
10.14359/6061
SP179-35
A.B. Ammar, J.M. Loche and P. Dumargue
Penetration of aggressive ions, such as chlorides, through concrete is one of the factors which causes to the depassivation of reinforcement and therefore may shorten the service life of a reinforced concrete structure. Most research work focusing on natural or accelerated diffusion tests generally rely on the validity of Fick’s laws. In this paper, we present both a new accelerated diffusion cell and an original test operating mode. The theoretical approach is based upon the study of diffusion-migration mechanism within the pore solution. The experimental results presented here have been obtained with tests on samples of saturated mortar.
10.14359/6062
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