Shear capacity, crack propagation and failure mechanism of reinforced concrete beams incorporating waste textile fiber and recycled aggregate concrete

Recycled concrete aggregate (RCA) can replace natural coarse aggregate at a limited scale without affecting concrete strength properties. However, high RCA content may weaken strength properties of concrete due to the presence of adhered mortar and weaker interfacial bonding which may be restored by adding fiber processed from textile wastes. In a view to understand the effectiveness of waste textile fiber (WTF) in concrete, the shear behavior of reinforced concrete (RC) beams made from RCA based TF reinforced concrete (RTFC) was investigated comprehensively. A systematic experimental program was conducted using 90 cylindrical specimens and nine reinforced concrete beam specimens with RCA replacement levels of 10%, 20%, and 30%, combined with textile fiber contents of 0.5%, 0.75%, and 1.0%. In this process, load-deformation responses, ultimate shear capacity, failure modes, crack patterns, and load-strain responses are examined explicitly. Additionally, the digital image correlation (DIC) was used to explore the concrete's strain distribution and crack propagation as load progresses to failure. Among the investigated mixtures, the specimen containing 30% RCA and 1.0% textile fiber demonstrated the most balanced structural performance in terms of strength and existing design codes consistently underestimate the shear capacity of the RTFC. According to the number of cracks, crack width, failure angle, post-diagonal cracking resistance, and DIC analysis, it is evident that the inclusion of a higher percentage of TF changed the failure mode from pure shear to flexure-shear in some cases. The results of this study may aid in formulating future design guidelines for RTFC, thereby transforming waste into resources for structural application.