Studying the possibility of structural performance improvement of RC beams made of lightweight Ponza aggregate with the addition of PWFs

The issue of reducing the weight of concrete structures while improving their properties and bridging cracks using fibres derived from plastic waste plays an important role in the development and production of sustainable concrete. This paper presents an experimental investigation of newly developed concrete specimens to evaluate the influence of the combined usage of plastic waste fibres (PWFs) and Ponza aggregate on the structural performance of reinforced concrete (RC) beams. This study focused on measuring the specimens’ deflection, ductility, toughness, and crack patterns. Twelve RC beams with a cross-section of 100 * 200 mm and a clear span of 1100 mm were subjected to two-point symmetrical loading until failure. Four groups of RC beams were investigated, corresponding to four concrete mixes containing different volume fractions (V_f) of polythene terephthalate PWFs (0%, 0.5%, 0.75% and 1%). Each group consisted of three RC beams with three longitudinal steel reinforcement ratios ranging from 0.00383 to 0.0087. The test results showed that adding PWFs enhanced the compressive and flexural strength of Ponza lightweight concrete by 9.3% and 56.4%, respectively, at a volumetric fibre ratio of 0.5%. However, the use of PWFs at higher ratios (0.75% and 1%) caused the compressive strength to decrease. Furthermore, the toughness of RC beams increased with the addition of PWF contents of up to 0.75% compared to those without containing PWFs. The maximum toughness increase of ~ 40% was recorded for the RC beam specimen reinforced with longitudinal steel reinforcement ratios equal to 0.00383 and a PWF Vf of 0.5%. The outcomes of this study have important implications for civil engineering applications that use structural members containing Ponza aggregate as a full replacement of natural coarse aggregate with the incorporation of PWFs to provide a new type of concrete that can be adopted by the construction industry.