Crack propagation and strain localization in metallic particulate-reinforced cementitious mortars

• No loss of mechanical strengths even at 30% OPC replacement by iron powder.
• Increase in ultimate strains and toughness when iron powder replaces OPC.
• Increase in elastic component of strain energy release on iron powder incorporation.
• Iron particulates beneficially modify the fracture process zone in OPC mortars.

The influence of replacing up to 30% of ordinary Portland cement (OPC) by volume with waste iron powder (containing a significant fraction of elongated particles) on the fracture response of composite mortars is reported. The increase in the overall strain energy release rate at higher particulate contents is dominated by its elastic component, which correlates well with the increase in length of the fracture process zone (FPZ), determined using digital image correlation. The tensile properties of the composites, determined from an analytical tension model, are also found to increase with iron powder content. The impact of metallic particulate incorporation was the most prominent in enhancing the tensile toughness of the composite rather than the strength or stiffness. It is shown that cementitious systems with enhanced toughness typically attained through the use of fiber reinforcement can be designed using metallic particulate reinforcement, at a much lower OPC content, which thus provides the composite with sustainability benefits also.

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