Study of P-h Curves on Nanomechanical Properties of Steel Fiber Reinforced Mortar

Steel fiber reinforced mortars with w/b 0.3 and 0.5 with and without 10% silica fume by cement weight were investigated using a Hysitron Triboindenter® with Berkovich tip, indenting in the interfacial transition zone (ITZ) between steel fiber and matrix, and also on the steel fiber and aggregate using 5mN maximum force to obtain P-h (Load-Displacement) curves for elastic modulus and hardness analysis. Different P-h curves were generated at different points in the ITZ region, steel fiber and aggregate. The P-h curves in the ITZ reached the maximum force at larger displacement than those of aggregate and steel fiber, revealing that the microstructures in ITZ are loosely packed together. The unit structures in steel fiber are mainly bound together in regular way by covalent bond; therefore, it reached the maximum force earlier than that of the actual igneous granitic aggregate. Varying irregular P-h curves were observed, mostly in the ITZ, and reasons for this are discussed; voids in microstructure, weak zone, possible voids beneath the indented point, indenting in varying unhydrated and hydrated phases, possible leaching/washing out of binder during polishing of non-epoxy-reinforced samples.