مهندسی عمران شریف (Aug 2020)
STUDYING THE STRENGTH AND DIFFUSION AND PERMEABILITY COEFFICIENTS OF CONCRETES CONTAINING SILICA FUME, FLY ASH, ZEOLITE AND LIMESTONE POWDER
Abstract
Permeability is an index, describing the easiness of fluid movement into a porous body, such as concrete. Water containing deleterious substances, such as chloride ions, sulfate ions, aggressive chemicals, etc. can penetrate into concrete and, subsequently, affects its short-term and long-term durability. Therefore, it is of great importance to evaluate the water permeability of concrete. For this purpose, the results of the permeability of the 7-day concrete specimens, containing silica fume, fly ash, zeolite, and limestone powder with replacement levels of 5, 10, 15 and 20 percentage of type II Portland cement mass are presented in this paper. ``Cylindrical chamber'' method, which was devised and developed by Naderi, was used during this investigation, for permeability measurements. Furthermore, one-dimensional permeability and diffusion coefficients, calculated based on cylindrical chamber test results, were used to evaluate the permeability of the concrete specimens. Percentage of the permeable pore space volume was also measured based on ASTM C642-06. The results tend to show that silica fume increases the compressive strength of the concrete specimen without any admixture (control specimen), while fly ash, zeolite, and limestone powder decrease the compressive strength of the control specimen. Moreover, the permeability and diffusion coefficients of the specimens containing the mentioned admixtures, except limestone powder with a replacement level of 20 percentage, were revealed to be lower than those of the control specimen. The results of the regression approach performed also show that the relationships between the dimensionless coefficients of permeability and diffusion and dimensionless coefficients of the test results (penetrated water depth, penetrated water volume, average water flow rate, and percentage of permeable pore space volume) can be estimated with high accuracy using the regression functions; however, no equation was found to estimate the relationship between the dimensionless coefficients of permeability and diffusion and compressive strength of the studied concrete specimens.
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