Abstract
This paper studies the effects of steel fibre geometry and architecture on the cracking behaviour of steel fibre reinforced concrete (SFRC), with the reinforcements being four types, namely 5DH (Dramix® hooked-end), 4DH, 3DH-60 and 3DH-35, of various hooked-end steel fibres at the fibre dosage of 40 and 80 kg/m3. The test results show that the addition of steel fibres have little effect on the workability and compressive strength of SFRC, but the ultimate tensile loads, post-cracking behaviour, residual strength and the fracture energy of SFRC are closely related to the shapes of fibres which all increased with increasing fibre content. Results also revealed that the residual tensile strength is significantly influenced by the anchorage strength rather than the number of the fibres counted on the fracture surface. The 5DH steel fibre reinforced concretes have behaved in a manner of multiple crackings and more ductile compared to 3DH and 4DH ones, and the end-hooks of 4DH and 5DH fibres partially deformed in steel fibre reinforced self-compacting concrete (SFR–SCC). In practice, 5DH fibres should be used for reinforcing high or ultra-high performance matrixes to fully utilize their high mechanical anchorage.
Highlights
IntroductionIt is well known that an addition of fibres to concrete is able to improve their tensile strength, fracture energy absorption and load bearing capacity (Romualdi et al 1968; Naaman 1972; Swamy 1975; Banthia and Trottier 1991; Abrishambaf et al 2013; Zhang et al 2014; El-Mal et al 2015; Li and Liu 2016)
The mechanical properties and post-cracking behaviour of steel fibre reinforced concrete (SFRC) greatly depend on the matrix properties in addition to the concentration, type, geometry, orientation and distribution of fibres, while the efficiency of fibre reinforcement depends on the deformed shape of the fibres, which enhances the anchorage mechanisms during the pulling-out
It appears that all mixtures had stable and excellent self-compacting properties (Table 3), adding steel fibres slightly affect the workability of SFRC-self-compacting concrete (SCC)
Summary
It is well known that an addition of fibres to concrete is able to improve their tensile strength, fracture energy absorption and load bearing capacity (Romualdi et al 1968; Naaman 1972; Swamy 1975; Banthia and Trottier 1991; Abrishambaf et al 2013; Zhang et al 2014; El-Mal et al 2015; Li and Liu 2016). The fibre contribution is mainly reflected when the concrete cracking initiates and often enhances the postcracking behaviour due to the improved stress transfer provided by the fibre bridging of the cracked sections (Islam and Alam 2013; Tadepalli et al 2015; Srikar et al 2016). The mechanical properties and post-cracking behaviour of steel fibre reinforced concrete (SFRC) greatly depend on the matrix properties in addition to the concentration, type, geometry, orientation and distribution of fibres, while the efficiency of fibre reinforcement depends on the deformed shape of the fibres, which enhances the anchorage mechanisms during the pulling-out. The distribution and orientation of fibres in hardened concrete are very much dependant on its fresh-state characteristics after mixing, namely, flowability, casting method, vibration and wall-effects introduced by the formwork (Abrishambaf et al 2013; Laranjeira de Oliveira 2010). It has been observed that an alignment of fibres in the direction of flow resulted in better post-cracking properties compared to those in the perpendicular direction (Abrishambaf et al 2013)
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