engleski

Air void analysis in the frost resistant concrete

Ability of concrete to resist physical actions due to freezing-thawing depends on it`s structure and can be determined on several ways. One of the methods is determination of compressive strength reduction after the exposure of concrete to a freezing-thawing cycling. This is indirect, phenomenological determination of microstructural changes reflected to a macro-level of observation. The other standard test method to evaluate frost resistance is approach on the mezzo-level by measuring the air void distribution with linear microscopical analysis. In this paper proportioning of frost resistant concrete is presented depending on the w/c ratio and amount of admixtures. Methods of testing frost resistance through the air void distribution are used. Properties of concrete in fresh and hardened state are measured. On the fresh concrete testing of temperature, density, workability and air void distribution is made. Air content is measured with the pressure method and instrument for the air void analysis (AVA). Air void analyzing instrument gives also the data about the air void distribution. On the hardened concrete testing of density, compressive strength and air void distribution with microscopical analysis is made. Methods of testing, accuracy of the measurement and results obtained on the fresh and on the hardened concrete are analysed. Testing is conducted in two laboratories (laboratory of the Civil Engineering Institute Zagreb, Concrete and Masonry Structures Department and laboratory of the Faculty of Civil Engineering in Zagreb, Department of Materials).

frost resistance; spacing factor; air content; de-icing salts

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