Comparative measurements of fracture toughgness combined with visual analysis of cracks propagation using the DIC technique of concretes based on cement matrix with a highly diversified composition

This paper presents comparative measurements of the fracture toughness together with visual analysis of cracks propagation of concretes made of quaternary binders. A composition of the 2 most commonly used mineral additives, i.e. fly ash (FA) and silica fume (SF) in combination with nanosilica (nS), has been proposed as a partial replacement of the ordinary Portland cement (OPC) binder. The primary objective of the proposed tests was to assess: basic mechanical parameters, i.e. compressive strength - f(cm) and splitting tensile strength - f(ctm), fracture toughnessK(Ic)(S), and fracture processes in quaternary concretes. The modern and precise DIC technique was used, during the studies, in order to realised assumed tasks. It was found that modification of the binder composition with 3 pozzolanic active materials resulted in an increase in the analysed mechanical parameters for each of the combinations compared to the results obtained for the control concrete. Substitution of the binder by 3 additives resulted in a slight heterogeneity of the structure of the quaternary binder concretes. In addition, as content of FA rises throughout each of quaternary concrete series, material becomes more ductile and shows less brittle failure. Therefore composite containing: 80% OPC, 5% FA, 10% SF, and 5% nS - due to its high fracture toughness and lower brittleness - can be used in reinforced concrete structures subjected to dynamic or cyclic loads.

Automated summary

This paper presents a comparative study on the fracture toughness and crack propagation of concretes made with quaternary binders. The use of mineral additives in combination with nanosilica as a partial replacement of ordinary Portland cement binder is proposed. The tests conducted aimed to assess the mechanical parameters, fracture toughness, and fracture processes of the concretes. The results showed that modifying the binder composition with three pozzolanic active materials increased the mechanical parameters compared to control concrete. Additionally, as the content of fly ash increased, the concrete became more ductile and exhibited less brittle failure. The composite with 80% OPC, 5% FA, 10% SF, and 5% nS showed high fracture toughness and lower brittleness, making it suitable for reinforced concrete structures subjected to dynamic or cyclic loads.