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This study aims to investigate the effect of shrinkage-reducing admixture (SRA) on the mechanical properties of ultra-high-performance fiber-reinforced concrete (UHPFRC). Three different SRA to cement weight ratios (0%, 1%, and 2%) were considered using the UHPFRC including 2% of smooth steel fibers by volume. The specimen without SRA exhibited the best performance in almost all aspects of the mechanical behaviors in compression, fiber pullout, and biaxial flexure including load carrying capacity, strain capacity, and energy absorption capacity (pullout energy and toughness). The mechanical performances deteriorated with the increase in the amount of SRA up to 2%. Finally, a suggestion was made to define the first cracking point of deflection-hardening UHPFRC under biaxial flexure stress. [ABSTRACT FROM AUTHOR]

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]

This paper presents the results of a study conducted to evaluate the possibility of utilizing the waste glass sludge (WGS) from the cutting and polishing process of glass plates, as a partial replacement of cement. A total of seven mortar mix proportions were prepared, by replacing ordinary Portland cement with WGS and/or fly ash (FA). The influences of WGS and FA on the compressive strength of mortars and ASR expansion of mortars were investigated. In addition, X-ray diffraction analysis was performed, to evaluate the pozzolanic activity. The results show that the incorporation of the WGS yields mortars with improved strengths at the later age (28 days), in comparison with that of a control mortar (ordinary Portland cement only); while the WGS caused a lower early strength than that of control, but higher than that of mortars containing FA. The ASR expansion of the mortars can be reduced by incorporating WGS as effectively as by fly ash. It is found that the consumption rate of calcium hydroxide for the paste with the WGS was faster than that of paste with FA, up to 28 days. These results indicate that the WGS has a higher reactivity than FA; and therefore, the WGS can be used as a pozzolanic admixture in cement composites. [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]