Concrete with fiber reinforcement is stronger and more ductile than concrete without reinforcement. Significant efforts have been made to demonstrate the properties and enhancements of concrete after reinforcement with various types and shapes of fibers. However, the issue of optimization in the reinforcement process is still unanswered. There is no academic study in the literature now available that can pinpoint the ideal fiber type, quantity, and shape and, more crucially, the overall technical viability of the reinforcement. The parametric analysis in this study determines the ideal shape, size, and proportion of fibers. The input and output parameters were separated from the optimization design variables. Input parameters included assessment of samples of fresh and mechanical concrete properties and the influence of type, length, and percentage of fiber on concrete performance. The aim was to establish the most efficient relationship between fiber dose and dimension to optimize the combined responses of workability and splitting tensile, flexural, and compressive strength. The mechanical and fresh properties of concrete reinforced with four different fibers, PFRC-1, PFRC-2, SFRC-1, and SFRC-2, were tested. The analysis showed that SFRC-2-20 mm-1%, with compressive, split tensile, flexural, and workability values of 44.7 MPa, 3.64 MPa, 5.3 MPa, and 6.5 cm respectively, was the most effective combination among the materials investigated. The optimization technique employed in this study offers new, important insights into how input and output parameters relate to one another.

Fibre-reinforced cementitious composites are highly effective for construction due to their enhanced mechanical properties. The selection of fibre material for this reinforcement is always challenging as it is mainly dominated by the properties required at the construction site. Materials like steel and plastic fibres have been rigorously used for their good mechanical properties. Academic researchers have comprehensively discussed the impact and challenges of fibre reinforcement to obtain optimal properties of resultant concrete. However, most of this research concludes its analysis without considering the collective influence of key fibre parameters such as its shape, type, length, and percentage. There is still a need for a model that can consider these key parameters as input, provide the properties of reinforced concrete as output, and facilitate the user to analyse the optimal fibre addition per the construction requirement. Thus, the current work proposes a Khan Khalel model that can predict the desirable compressive and flexural strengths for any given values of key fibre parameters. The accuracy of the numerical model in this study, the flexural strength of SFRC, had the lowest and most significant errors, and the MSE was between 0.121% and 0.926%. Statistical tools are used to develop and validate the model with numerical results. The proposed model is easy to use but predicts compressive and flexural strengths with errors under 6% and 15%, respectively. This error primarily represents the assumption made for the input of fibre material during model development. It is based on the material's elastic modulus and hence neglects the plastic behaviour of the fibre. A possible modification in the model for considering the plastic behaviour of the fibre will be considered as future work.

Steel fibre-reinforced concrete has been used extensively because of its excellent mechanical properties. Academic researchers have comprehensively discussed the impact and challenges of fibre reinforcement to obtain optimal properties in the resultant concrete. Most researchers reported the mechanical performance of fibre-reinforced concrete (FRC) under static loads. A few studies did conclude the mentioned performance on dynamic loads. However, a comprehensive analysis is still missing that can explain the crack resistance performance of FRC under dynamic loads at relatively high temperatures. In this study, the efficacy of FRC beams for crack resistance is analyzed under coupled loads, i.e., dynamic load at relatively high temperatures as compared to room temperature. Various researchers found that concrete's qualities may change at different temperatures due to moisture content, physical and chemical changes to the ingredients, differences in cooling and heating schedules, water-to-cement ratio, and aggregate. The rate of reduction in moisture content is quite possible even in relatively high temperatures as compared to standard room temperature. Therefore, we selected a range of temperature that demonstrate tests on more realistic weather conditions for most of the concrete applications. As per theory, a slight change in modulus or strength shall definitely effect the dynamic response. Therefore, we tested cantilever FRC beams on a modal excitor in a band heater to expose the beams to bending loads at different temperature values. The variation in the beam's dynamic response parameters, including modal amplitude and frequency, is discussed, and compared with experimental results for regular and reinforced concrete beams. The SIF of plain concrete decreased as concrete temperature increased. Compared to conventional concrete, using SFRC1 enhanced fracture resistance by 10-20% at various crack depths (2 mm, 4 mm, 6 mm) and temperatures (20 degrees C, 40 degrees C, 60 degrees C).

This review article presents a critical analysis by compiling the previous research studies with an emphasis on the optimization of fibre reinforced concrete to enhance its strength against different load regimes with a special focus on thermo-mechanical load conditions. The historical background, a description of the evolution of concrete as a material for advanced structures, and the fundamental principles of concrete production are provided as a preamble. Later, a discussion on FRC, fibre types and shapes, mixing methods and testing of properties is provided. A separate section describes how fibre mixing can affect fatigue and fracture behaviour, especially under different load regimes. Gaps in the existing research with possible new directions are discussed in the conclusion.