| Summary: | The work described in this thesis has been performed in order to gain further understanding of the relationship between the microstructural characteristics of some common types of medium to high strength sustainable Self- Compacting Concretes (SCCs) (especially the internal pore structure, the interfacial transition zone (ITZ), and chemical composition) and the carbon dioxide and chloride diffusivities. This was done by evaluating the diffusion coefficients with the aid of some selected and modified accelerated tests at the macro scale.
The internal composition and microstructure form were quantitatively analyzed for one normal vibrated concrete (NVC), one normal SCC mix (R-SCC) and three different types of sustainable SCCs with relatively high partial replacement of cement at micro and nano scales and linked with the macro scale tests. This was done by using a wide range of advanced techniques such as thermo gravimetric analysis (TGA), x-ray diffraction (XRD), mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). In addition, the penetration parameters from the macro short term tests were used to simulate the results mathematically in order to assess the long term behaviour of the concrete mixes.
Possible mechanisms, in multi-scale terms, are proposed to explain the overall response of both normal and sustainable medium to high strength grade SCCs to the degradation caused by carbonation and chloride penetration in harsh environments. The findings of the research will contribute to deeply understand the role of the internal microstructure of sustainable SCC in determining the carbonation and chloride penetration. The recommendations derived from this research are fundamental to achieving more durable sustainable SCC with longer service life for applications in aggressive environments.
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