Study of the interface between the steel fibre and cement-paste by scanning electron microscope and energy dispersive X-ray analysis

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Volume Title
Insinööritieteiden korkeakoulu | Master's thesis
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Date
2016-12-12
Department
Major/Subject
Structural Engineering
Mcode
R3001
Degree programme
Master's Degree in Structural Engineering and Building Technology
Language
en
Pages
44+7
Series
Abstract
The morphology of the interfacial transition zone, (ITZ), present at steel fibre and cement-paste interface was studied by using the environmental scanning electron microscope. Based on the available literature, the ITZ is the weakest and most porous layer connecting the constituents of the composite and which is important for the tensile capacity of the concrete reinforced with steel fibre. The micro-structures of the ITZ and bulk cement-matrix are different. Different cement-paste recipes and curing conditions were examined in the study. The samples were investigated by using the environmental scanning electron microscope and energy dispersive X-ray analysis. The backscattered and secondary electron detectors were employed. The images with the resolution of 500 μm were made to study the geometrical characteristics of steel fibres used. The resolution of 5 μm was used to identify the stiction between the steel fibre and cement-paste.The chemical consistency within the ITZ layer was specified by X-ray detector, by which calcium hydroxide, (CH), and calcium-silicate-hydrate crystals , (C-S-H), and the agglomeration of silica fume were detected. The results demonstrated that the presence of the gap between the steel fibre and cement-paste was observed in 80% of the cases studied. The particles of CH and C-S-H were sticked to the surface of the steel fibre, but they were not connected to the bulk cement-paste. The stiction between the steel fibre and cement-paste was the lowest in samples with the silica fume. The study support an assumption that the adhesion at the interface between the steel fibre and cement-paste may not exist.
Description
Supervisor
Puttonen, Jari
Thesis advisor
Eik, Marika
Keywords
Interfacial transition zone, scanning electron microscope, steel fibre reinforced concrete, energy dispersive X-ray, adhesion
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