Flexural behavior of plain concrete beams containing strain hardening cementitious composite layers with High-Volume fly ash

Abstract Recently, there has been an ongoing interest in the use of fly ash as an alternative to reduce cement content in cementitious composites. The addition of high-volume fly ash (HVFA) into strain hardening cementitious composites (SHCCs) as a strengthening layer for concrete not only improves the flexural performance, but also provides a sustainable approach to address a severe environmental concern. In this contribution, an experimental program was undertaken to determine the influence of SHCCs containing high-volume fly ash (HVFA-SHCC) working as a strengthening layer in a plain concrete beam on the flexural behavior of the layered structure, considering the layer thickness, re-curing conditions and curing time. The crack patterns, mid-span strain distributions, and load deflection curves were obtained based on a four-point bending test. Compared to that for the plain concrete, the specimens containing the HVFA-SHCC layer exhibited excellent crack control, and their failure mode gradually changed from flexure failure to shear failure with increased layer thickness. Moreover, a remarkable improvement in the strain hardening behavior was also found as increasing the layer thickness. Furthermore, an ultimate flexural toughness ratio was proposed, which has proven to be a valuable method to evaluate the flexural toughness of plain concrete beams containing HVFA-SHCC layers under different deformation conditions. The present study suggests that the optimal layer thickness of HVFA-SHCC is in the range of 25%-35% of the beam height in view of the flexural performance and cost. In addition, an improved flexural performance of a plain concrete beam containing an HVFA-SHCC layer is expected in an alkali environment.