My research project
Optimising structural elements containing hybrid fibre-reinforced concrete
Globally, concrete is the most widely used man-made construction material. This is due to its combination of flexibility of form, wide availability, and balance of cost and strength when compared to alternative materials (P. Kumar Mehta et al, 2006). The low tensile strength and strain capacity are some of the undesirable properties of concrete as they can cause failure to occur shortly after the formation of the first crack (Amir Alani et al, 2013). These properties of mass concrete have led to the use of steel reinforcement (rebars) to improve its tensile properties. However, the use of steel reinforcement carries durability implications such as the corrosion of the embedded steel among others (Per Jahren et al, 2014). An alternative method of concrete reinforcement has been the introduction of short-fibre into the concrete, examples include steel, polypropylene and glass fibres. The addition of these fibres to concrete influences the manner in which cracks develop (Amir Alani et al, 2013) as well as increasing the strain capacity at peak load, and provides significant energy absorption in the post-peak portion of the load vs. deflection curve (L.N.Vairagade et al, 2015).
A number of research studies have looked at how the introduction and dosage of fibres in a concrete mix affect mechanical properties, and there exists a body of guidance documents on the use of short-fibre steel, polymer and glass reinforced concrete. However, only a limited amount of research has considered the effect of mixing different fibre types to form mixed fibre composites. To date there has been no coherent study of the “hybrid” effect of using combinations of short-fibre reinforcement with significantly different stiffness and strength in order to identify combinations that yield the best properties (toughness, bond strength, etc.) and the potential structural benefits of such hybrid composites. Hence, an investigation into the benefits of hybrid, short-fibre reinforced concrete and its use for structural advantage needs to be conducted. The research focus on short fibres thus requires that these materials be optimized for use in large engineering components and structures to commercial and engineering advantage. To adequately perform structural element optimization, extensive material testing will be conducted comparing the performance of plain concrete and concrete containing short fibres such as steel, polypropylene, glass, etc. In addition to this, testing of large elements will be conducted to investigate component property. In terms of the material properties of the concrete the samples tested will be of the scale 10–20 cm whereas a scale of about 1–3 m will be used for structural elements. The experimental results will be compared with the output of finite element models to gain a further understanding of the structural implications of short fibre additions.
The outcome of this study will provide a better understanding of the structural performance of short-fibres and their potential for cost optimization in construction through a reduced requirement for link reinforcement, a faster construction cycle and also a better structural performance.