THE TOUGHNESS OF STEEL FIBRE REINFORCED CONCRETES

Preliminary comparison tests were carried out fibre reinforced concretes (FRC) made with two types of well-known, marketed foreign steel fibres and with a Hungarian one, used beforehand successfully in the industry to improve the toughness, of e.g. plain concrete SIOME tubes. The evaluation of toughness indices I and residual strength factors R based on flexural data (ASTM C 1018) and equivalent strength (Japanese Standard) have shown that the Hungarian fibres are at least of the same quality as foreign ones, mainly in respect of overall toughness nevertheless the near-after-crack behaviour (crack arrest) can be estimated correctly applying neither of these methods in itself. Splitting tests on cylinders and load-horizontal strain (or crack width increment) diagrams are helpful in estimating the overall toughness in cracked condition. The first crack load was not influenced by the fibres in any case, but moisture content and curing conditions were decisive factors.