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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:
SP132-35
Date:
May 1, 1992
Author(s):
Akthem A. Al-Manaseer, Muir D. Haug, Moir D.Haug and Lionel C. Wong
Publication:
Symposium Papers
Volume:
132
Abstract:
Study examines the microstructure properties of cement-based grout consisting of Type II rapid-hardening portland cement, Saskatchewan fly ash, and brine. The liquid brine is composed mainly of salts of sodium, calcium, potassium, and magnesium obtained from an underground potash mine. A scanning electron microscope (SEM), with an electron probe x-ray microanalyzer, was used to study the mechanism by which fly ash and brine alters the microstructure characteristics of cement grouts under confining pressures of 0, 3.4, and 6.9 MPa (0, 500, and 1000 psi). The SEM examination was conducted at 7, 14, and 365 days. This examination revealed that grout mixes containing brine had a gel-like substance covering the entire surface of the hydrated products. The probe x-ray microanalyzer identified the gel-like substance as consisting mainly of sodium chloride salt. Fly ash cement particles were also found to be encapsulated by the sodium chloride gel-like substance. This encapsulation may decrease the rate of pozzolanic reaction between fly ash particles and the lime available in the cement. Microscopic examination of specimens mixed with brine also showed the presence of long fibrous crystals with diameters ranging from 3 to 20 æm growing on the surface of the gel-like substance. Generally, at 7 and 14 days, the fly ash-cement grouts were found to have more such fibers than the grout containing no fly ash. This trend reversed at 365 days.
DOI:
10.14359/2093
SP132-36
J. A. Larbi and J. J. M. Bijen
The interface between the cement matrix and aggregate is mostly regarded as a weak link in concrete with respect to durability and strength. It is shown that the positive effects of pozzolans on the permeability of concrete are partly related to a decrease in the thickness of the weak, lime-rich, interfacial zone. Results for various mineral admixtures, such as ground granulated blast furnace slag, powder coal fly ash, silica fume, a synthetic colloidal silica, and metakaolinite are presented. It is shown that in the presence of mineral admixtures, the calcium hydroxide content in the interfacial zone is reduced substantially.
10.14359/2111
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
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