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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 74 Abstracts search results
Document:
SP192-70
Date:
April 1, 2000
Author(s):
K. Watanabe, K. Yokozeki, N. Otsuki, and M. Daimon
Publication:
Symposium Papers
Volume:
192
Abstract:
Leaching degration of cement composites is a phenomenon involving the removal of various solid constituents and may result in loss of strength. The leaching of calcium is not a major problem for most concrete structures, as the degradation rate is very slow. However, it is important for structures such as marine structures, dams, and radioactive-waste repositories that are in an environment that direct contact with water for a long term. In order to evaluate the leaching behavior, investigation of the fundamental degradation mechanism must be undertaken. Described in this paper is the degradation mechanism of cement composite derived from accelerated testing. Investigations were conducted using three different accelerated test methods, I.e. the immersion test method, the dissolution test method and the permeation cell test method. The main results of the study were as follows: 1) 30-50% of calcium in cement composites was leached out in several moths in the accelerated tests (the immersing test method and the permeation test method); 2) in all tests, calcium leaching from Ca(OH)2 and C-S-H was observed, and the change in the porosity and physical properties corresponding to the leaching degree was found; and 3) a possibility to predict the long-term degradation behavior of structures by using numerical analysis was demonstrated.
DOI:
10.14359/5807
SP192-71
J. A. Grijalvo, M. T. Blanco-Varela, F. P. Maroto, A. P. Sanchez, and T. V. Moreno
The state-of-the-art on thaumasite formation is discussed, stressing aspects of its formation in mortars an in portland-cement concretes, and also the effect its formation has on their durability. Methods for material synthesis, mentioned in the bibliography including a detailed report of the characterization of thaumasite through XRD, IR, DTA/TG, NMR, electron microscopy and microanalysis, are described.
10.14359/5808
SP192
Editor: V.M. Malhotra
SP192 In 2000, CANMET, in association with ACI, the Japan Concrete Institute, and several other organizations in Spain and Canada, sponsored a fifth international conference held on June 4-9, 2000, in Barcelona, Spain. More than 120 papers from 35 countries were received and peer reviewed in accordance with the policies of the American Concrete Institute; 73 were accepted for publication. The accepted papers deal with all aspects of concrete durability. In addition, several sessions dealing with sulfate attack, superplasticizers and supplementary cementing materials, and near surface testing for the durability of concrete were organized. In addition to the papers that have been published in the refereed proceedings, more than 30 papers were presented at the conference.
10.14359/14232
SP192-11
V. G. Papadakis
For comparing the relative performance of supplementary cementing materials (SCM) with regard to concrete durability, the concept of efficiency factor may be used. The efficiency factor (k-value) is defined as the part of the SCM in an SCM-concrete which can be considered as equivalent to portland cement. In this work, three typical SCM were studied: a silica fume, a low-calcium fly ash and a high-calcium fly ash. Accelerated carbonation and chloride penetration tests were performed. With regard to 28-day compressive strengths, penetration test were performed. With regard to 28-day compressive strengths, k-values of 3, .5, and 1 for silica fume, low-calcium fly ash, and high-calcium fly ash, respectively, were estimated. Mathematical models describing the carbonation propagation and chloride intrusion were applied to estimate the durability k-values. Higher k-values with respect to chloride penetration were found, indicating that SCM reduce the chloride permeability more effectively than they improve the compressive strength. On the contrary, with respect to carbonation depth, k-values of .3, .5, and .7 for silica fume, low-calcium fly ash and high-calcium fly ash, respectively, were estimated. A theoretical explanation of these results is also given.
10.14359/5748
SP192-12
J. Malolepszy and Z. Pytel
This study evaluates effect of metakaolinite on the chemical resistance of standard cement mortars produced from portland cements of different C3A content, ranging from 3.3% to 11.4%. The metakaolinite was produced by burning of kaolin clay at different time and temperatures, specially selected to ensure the highest pozzolanic activity, as measured by ASTM method. The chemical resistance was evaluated through the measurements of strength, shrinkage and expansion tests on the samples stored in water and chemical solutions. The porosity and microstructure was also investigated. As it appeared, the metakaolinite admixture did not change substantially the standard properties of mortars, though their chemical resistance was markedly improved.
10.14359/5749
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