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Abstract

The objective of this investigation was comparing the penetration of chloride ions in ordinary and air-entrained concretes containing a waste material Fluidized Bed Combustion Fly Ash (FBCFA). All concretes were tested with 15% and 30% cement replacement by FBCFA, with the same water-binder ratio of 0.45. Two kinds of fly ash coming from fluid bed combustion in two power plants in Poland have been used. In this study the rapid chloride permeability test – Nordtest Method BUILD 492 method – was used. The microstructure of the concrete was analyzed on thin polished sections and the measurement of air voids sizes and their distribution, using digital image analysis, was carried on according to PN-EN 480-11:2008. Obtained results have shown a significant influence of partial cement replacement by FBCFA on the chloride ions movements in concrete. It has been found that this kind of addition reduced considerably the chloride ion penetration. The influence of air entrainment on the chloride diffusion coefficients was also measured and it was shown that application of air-entraining admixture for concretes with FBCFA reduce the chloride diffusion coefficient but it should be used with caution.
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Abstract

Industrial utilization of fly ash from various kinds of fuel plays an important role in the envi-ronmentally clean and cost effective power production. The primary market for fly ash utilizationis as a pozzolanic addition in concrete production. The paper concerns the concretes containingfly ash called Fly Ash from Biomass (FAB) from co-combustion of hard coal and wood biomass(wood chips). Characterization of the fly ash was carried on by means of X-ray diffractometryand E-SEM/EDS analysis. The results of laboratory studies undertaken to evaluate the influence of FAB on concrete resistance to surface scaling due to cyclic freezing and thawing in the presenceof NaCl solution were presented. The tests were carried out for concretes containing up to 25% offly ash related to cement mass. Additionally, the microstructure of air-voids was described. It was concluded that the FAB has significant effect on concrete freeze/thaw durability. The re-placement of cement by fly ash from co-combustion progressively transformed the concrete mi-crostructure into less resistant against freeze/thaw cycles and excessive dosage (over 15%) maydangerously increase the scaling.
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