DescriptionABSTRACT The target of the study is to improve understanding of the interfacial transition zone (ITZ) around short steel fibres in concrete. The concrete reinforced by short steel fibres, SFRC, is made by mixing fibres to a fresh concrete mass to increase ductility and crack resistance of the hardened concrete. In addition to the orientation of fibres within the concrete matrix, the load bearing behaviour of SFRC depends on adhesion or bond of the cement-paste to steel fibres and aggregates. The present research project is focused on the study of physio-chemical properties of adhesion and the changes in the ITZ under external loading when the adhesion will be lost gradually. The adhesion layer -interfacial transition zone (ITZ)- is forming between fibre, cement-paste and aggregates. Loss of adhesion between steel fibres and cement-paste leads to crack initiation and development of cracking influencing the failure mechanism of SFRC. The chemical composition of cement-paste is complicated and the actual structure of the zone around fibres or aggregates is poorly known. The micro-structure of the hardened cement-paste in general depends on a hydration process, which is defined by a chemical composition of cement clinker and possible admixtures used in concrete mix. The micro-structure of the cement-paste in ITZ still differs from that of the bulk one. The investigation of the interaction between fibres and concrete utilizing X-ray micro-computed tomography (micro-CT) enables to assess accurately the physical characteristics of adhesion present at the interface between steel fibre and cement-paste. Within the study, SFRC samples were scanned by high resolution micro-CT to evaluate the morphology of the ITZ layer including its porosity, thickness and continuity due to the aggregates or already developed micro-cracks. To study the influence of chemical consistency of the cement-paste on the structure of the ITZ layer, the SFRC samples scanned were made of different cement recipes.
|Period||11 Jul 2016 → 14 Jul 2016|