Effect of natural fiber type and angle of interface on the interfacial bond characteristics of ultra-high toughness cementitious composites

The bond strength among the prevailing structure and repair material is important for performing the retrofit/rehabilitation operations. A solid bond warrants that both current and repair components function effectively, enhancing structural performance in terms of stiffness, ductility and performance. However, a weak link could cause inefficiencies in the transfer of load and sometimes lead to the collapse of entire building. Due to these grounds, the value of bond strength plays a crucial role in structural elements requiring retrofit/rehabilitation operations. In this work, an effort is made to understand the bond performance of a novel retrofitting material produced using natural fiber-based ultra-high toughness cementitious composites (UHTCC). The overall objective of the proposed work is to know the effect of the angle of interface (Ψ) and type of natural fibers on the interfacial shear resistance of UHTCC. The test matrix includes two major parameters namely (a) the angle of the interface (Ψ = 30°, 35°, 40°) under slant shear compression and vertically cut specimens under split tension test (b) the type of natural fiber used (flax, hemp). From the observed results, for the flax UHTCC samples, the shear stress (SS) values increased by 40.26% at 30° to 35° and by 0.64% at 35° to 40° angle of interface. For the hemp samples, the SS values increased by 5.9% and decreased by 14.48% at the same angles. The theoretical procedure developed using the Mohr theory showed an adhesive failure envelope thereby portraying the effectiveness of the proposed UHTCC matrix as repair material. From the Life Cycle Assessment (LCA), the use of natural fibers showed a significant reduction in cost, energy, and carbon footprint when compared to the commercial fibers (PVA, PP etc.) based UHTCC matrix.