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The aim of this investigation was to study the factors influencing the mechanical tensile properties of steel-fibre-reinforced concrete exposed to high temperatures. The properties were estimated by the double-punch test having a high accuracy. Specimens reinforced with fibres of two types (twisted or hooked), two aspect ratios ( l / d = 60 or 80), and three fibre contents (volume fractions of 0.25%, 0.5%, or 1%) were tested after exposure to four different maximum temperatures (room temperature, 300 °C, 500 °C, and 700 °C). Test results show that the residual compressive strength, DPT tensile strength and rupture energy of the specimens decreased with their increased heating. After the SFRC was exposed to the high temperatures, the relative loss in tensile strength was higher than that in compressive strength, but the relative loss of rupture energy was comparatively lower. After exposure to high temperature, the behaviour of the samples was more sensitive to the volume fraction and aspect ratio of the fibre than to its type. The coefficients of variation (COVs) of the rupture energy for SFRC specimens heated to higher temperatures is similar to those of the tensile strength, although the results are considerably more scattered than the compressive strength. A model predicting the residual tensile strength of heated SFRC measured by the DPT was proposed based on the test results. [ABSTRACT FROM AUTHOR]

Waste glass sludge (WGS), a byproduct of glass plate manufacture, was used to improve the durability properties of concrete under an environmental condition of freezing and thawing, with the existence of de-icing salts. A total of five concrete mix proportions were prepared, by varying the amounts of WGS. In order to observe the effects and roles of WGS on the durability performances of concrete mixtures, compressive strength tests, freezing and thawing tests, chloride ion penetration and surface scaling were carried out. Test results showed that the incorporation of WGS as a partial replacement for cement has beneficial effects on the compressive strength of concrete, especially when used together with fly ash. Moreover, WGS improved the resistance of freezing and thawing with and without de-icing salts, the chloride ion penetration and the resistance of surface scaling of the concrete compared to the control mixture containing 20% fly ash as cement replacement. [ABSTRACT FROM AUTHOR]

Abstract: The biaxial flexure test (BFT) method for the biaxial tensile strength of concrete has been improved. To ensure the equi-biaxial stress condition during the test, the geometry of the specimen, proper treatment of the specimen surface, and the support conditions were proposed. The biaxial flexural strength of concrete was measured with the improved biaxial flexure test method. The coefficient of variation (c.o.v) of the biaxial flexure test method is comparable to that of the four-point bending test and ASTM C 1550. The improved biaxial flexure test provides a practical and reliable means of determining the biaxial flexural strength of concrete. The biaxial tensile strength given by the biaxial flexure test method and the ASTM C 1550 method is greater than the uniaxial tensile strength using the four-point bending test method. [Copyright &y& Elsevier]