Effect of Macro-Synthetic Fibre Incorporation on the Mechanical and Dynamic Properties of Cementitious Composites and Fractal Analysis

To improve the brittle behaviour and flexural capacity of conventional concrete, fibres with different properties and proportions are added to the mix. In recent years, with advances in concrete technology, studies have focused on cement-based composites that use only fine aggregates and exhibit strain-hardening behaviour, offering enhanced crack control and durability. This study investigates the effects of polymer-based macro synthetic fibres (MSFs), with high tensile strength and corrosion resistance, on the engineering properties of such composites. Five mixtures were prepared with varying fibre lengths (10 mm, 17 mm) and dosages (0.25%, 0.50%). Mini Flow Table, ultrasonic pulse velocity, compressive and flexural strength, and Charpy impact tests were conducted, and fractal analysis was used to evaluate crack development. Results showed that MSF addition improved ultrasonic pulse velocity and dynamic elastic modulus and increased compressive strength regardless of fibre length or content. Shorter fibre length led to increased compressive strength, whereas increasing fibre content from 0.25% to 0.50% resulted in a decrease. A similar trend was observed in the flexural strength. MSF significantly improved Charpy impact energy, increasing it by up to 100%. Fractal dimension values supported the mechanical and dynamic behaviour of the composite, indicating fibre usage increased fracture energy and the energy required for crack formation.