Abstract
A systematic investigation of the effects of silane coatings on steel fibre–mortar interfacial bond properties was conducted, combining pullout tests, analytical solutions, and meso-scale FE simulations. Nine silane coatings were tested, and their effects were evaluated by 30 single fibre pullout tests. They were found to increase the peak force and energy consumption up to 5.75 times and 2.48 times, respectively. Closed-form analytical solutions for pullout load, displacement, and interfacial stress distribution during the whole pullout process were derived based on a tri-linear bond-slip model, whose parameters were calibrated against the pullout tests. Finally, the calibrated bond-slip models were used to simulate the pullout tests and complex failure of multi-fibre specimens in mesoscale finite element models. Such an approach of combining pullout tests, analytical solutions, and mesoscale modelling provides a reliable way to investigate the effects of fibre–mortar interfacial properties on the mechanical behaviour of steel fibre reinforced concrete members in terms of structural strength, stiffness, ductility, and failure mechanisms.
Highlights
IntroductionSteel fibre reinforced concrete (SFRC) has higher tensile/flexural/compressive/fatigue strengths, fracture toughness, and ductility than plain concrete [7,8,9,10] due to the crack-bridging effect of steel fibres, which delays crack initiation and propagation in concrete [11,12]
This study aims to systematically identify optimal silane coupling agents for coating steel fibres used in Steel fibre reinforced concrete (SFRC), by a combination of laboratory experiments, analytical analysis and numerical simulations
(Z1–Z4) are four Dow Cornings® silane-based coupling agents, including amino-propyl-triethoxy-silane (Z6011), amino-propyl-tri-methoxy-silane (Z6020), methyl-propyl-acyloxypropyl-trimethoxy-silane (Z6030), and glycidyl-ether-oxypropyl-trimethoxy-silane (Z6040); (b) Group ZZ (ZZ1–ZZ4) are compound solutions with the above four silane coupling agents added with Zr(NO3 )4 ·5H2 O crystals; (c) Group ZH2 is the Z6020 solution mixed with H2 ZrF6 solution (45% wt) since H2 ZrF6 has notable effects on anti-corrosion of steel plates [39]
Summary
Steel fibre reinforced concrete (SFRC) has higher tensile/flexural/compressive/fatigue strengths, fracture toughness, and ductility than plain concrete [7,8,9,10] due to the crack-bridging effect of steel fibres, which delays crack initiation and propagation in concrete [11,12]. Such effect is mainly dependent on the interfacial bonding properties and energy dissipation between fibres and mortar during fibre pullout. Improving the interfacial properties between these two materials is, important for SFRC to achieve better macroscopic mechanical performances
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