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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 90 Abstracts search results
Document:
SP132-51
Date:
May 1, 1992
Author(s):
V. G. Batrakov, S. S. Kaprielov, and A. V. Sheinfeld
Publication:
Symposium Papers
Volume:
132
Abstract:
Results of an investigation of cement paste structure, and strength, permeability, and frost resistance of concrete with admixtures of silica fume type are given. The admixtures are waste materials from metallic silicon, low-grade ferrosilicon, ferrosilicon chrome production, containing SiO2 in the amount of 92, 70, and 66 percent, and surface area of 25.0, 44.9, and 18.5 mý/g, respectively. The influence of the admixtures on the cement paste microstructure results in an increase of gel porosity volume, decrease of capillarity porosity, and in an increase of strength. Thus, concrete strength increases and its permeability decreases. Physical and chemical properties of the silica fume-type admixtures insignificantly affect gel pore volume, whereas they have significant influence on capillary porosity. An increased dosage of high-range water-reducing admixture (HRWR) is a beneficent factor in increasing hydration degree and gel porosity, decreasing capillary porosity volume, and, consequently, increasing strength. Concrete frost resistance with silica fume dosages up to 10 percent of cement mass is not lower than the reference concrete with the same amount of binder.
DOI:
10.14359/2348
SP132-37
A. Carles-Gibergues and B. Husson
Within the context of atmospheric pollution prevention, fly ash producers are brought to better desulfurize combustion gases. As a result, there are important modifications in the composition of the residues that are enriched with sulfur, especially in the case of calcium sulfite fly ash. The sulfitic fly ashes studied result from desulfurization by quick lime addition in dust removers of a thermal plant. Paper presents the physical, chemical, and mineralogical characteristics of this type of fly ash. Their examination by x-ray diffraction shows the presence of crystallized minerals: lime, calcite, and calcium sulfite, and the existence of a glass, the composition of which is given by electron microprobe. A special emphasis is given to the sulfite stability. In a second part of the paper, the behavior of these fly ashes in paste with water and slaked lime has been studied. It is shown that they are a very weak hydraulic binder but they present, on the other hand, pozzolanic activity. At last, the study has allowed determination of the influence on workability and mechanical properties of hydraulic mortars and concretes in which they have been introduced as partial replacement of cement. Corrosion and carbonation aspects have also been studied in mortars.
10.14359/2121
SP132-40
J. Ambroise, S. Martin-Calle, and J. Pera
After calcination at 650 to 850 C, kaolinitic clays show an interesting pozzolanic property. Thermal activation leads to metakaolin, an amorphous phase which is very reactive. In this study, different clays were tested with various granular sizes and calcination parameters. The pozzolanic properties were investigated using metakaolin-lime mixtures by the evaluation of both the mechanical strength and combined lime. The mineralogical composition, particle size distribution, and degree of amorphousness were the main factors affecting the pozzolanic activity of calcined clays. Influence of the pozzolanic activity on the mechanical and durability properties of concrete was established from test results on blended portland-metakaolin cements.
10.14359/2133
SP132-42
T. Marwan J. Pera, and J. Ambroise
When heated at 800 C for 5 hr, Indonesian laterites showed good pozzolanic activity. The kaolin content of the material is the main cause of pozzolanicity, as indicated by the lime reactivity. Blended portland cements containing 20, 30, 40, and 50 percent of calcined laterite admixture were studied. Concretes were made with such cements and placed in aggressive solutions: seawater, acetic acid, and sulfuric acid. The best results were obtained with a cement containing 30 percent of calcined laterite admixture.
10.14359/2144
SP132-43
R. Breitenbucher, R. Springenschmid, and H. W. Dorner
In tunnels built according to the New Austrian Tunnelling Method, the shotcrete shell is often in contact with ground water. Depending on the amount and type of water, chemical compounds in the shotcrete are dissolved and transported into the drainage pipes and the main outfall. Due to precipitation of the dissolved compounds, the maintenance of the drainage systems is very expensive. Furthermore, the main outfall is loaded with water of a high pH-value. It was found that as well as Ca(OH)2, the alkalies in the shotcrete are responsible for the degree of leaching. Therefore, the accelerators needed for such shotcretes, which are based mostly on alkalies, have to be reduced as much as possible. This can be done sufficiently if silica fume is used in connection with slag cement to make the shotcrete sticky enough, so that it adheres to the rocks.
10.14359/2155
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