Shear behaviour of E-UHPC containing recycled steel fibres and design of E-UHPC screw piles

M.N Isa,Kypros Pilakoutas,Maurizio Guadagnini

doi:10.1016/j.conbuildmat.2021.124555

M.N Isa, Kypros Pilakoutas + Show 1 more

https://doi.org/10.1016/j.conbuildmat.2021.124555

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Abstract

The shear behaviour of Eco-Efficient Ultra-High Performance Concrete (E-UHPC) has not been investigated until now and this limits the potential applications for this material that uses low-cost and sustainable constituent materials including Recycled Tyre Steel Fibres (RTSF) and Recycled Tyre Steel Cords (RTSC). The potentially high shear resistance of E-UHPC could enable its use in more complex applications such as screw piles, something not easily achievable with conventional concrete. This study presents experimental and numerical work to address this research gap. It provides a detailed account of the experimental testing of 13 E-UHPC mixes containing various dosages of recycle steel fibres. Prismatic specimens are tested under an asymmetric four-point loading configuration and their deformation response is used to investigate the shear performance of the studied mixes. The shear stress – strain behaviour as well as shear modulus is determined. The results show that mixes containing RTSC can develop a high shear strength at the level of their flexural strength and comparable to that obtained from mixes with manufactured steel fibres. While mixes containing RTSF overall have lower shear strengths, high shear strengths can be achieved by using higher dosages of RTSF or using hybrid mixes of RTSF and RTSC. Shear strength prediction models based on flexural properties and fibres dosage are proposed for design purposes. An E-UHPC screw pile design model is developed for screw pile use in foundations of light and medium weight structures. Theoretical and physical modelling of the E-UHPC screw pile model is carried out and a design guideline is proposed. E-UHPC screw piles can offer various practical advantages, including rapid installation, immediate load carrying capability, minimal site disturbance, resistance to wide load applications, i.e. compression and tensile loads, and will solve the corrosion vulnerability of steel screw piles.

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