The research reported in this thesis deals mainly with the use of novel nanotechnology-based testing methods in the field of cement-based composites. The existing knowledge of indentation test methods is presented and reviewed. The research presented focuses on the development and pilot usage of depth-sensing indentation (DSI) test methods. The use of DSI test methods for cement-based materials covers two distinct areas. The first area includes the testing of micromechanical properties of cement pastes/matrices. The development in DSI test methods allows direct measurements of properties, such as hardness, elastic modulus, etc., at microscale. Special attention is paid to assessment of interfacial regions in such cement-based materials. In the second area, DSI test methods are used for assessment of interfacial properties of fibre reinforced cementitious composites, with focus being directed to composites reinforced by bundles of microfilaments. A new push-out test method for individual microfilaments collated in a bundle and embedded in cementitious matrix is proposed and developed. Novel use of other nanotechnology-based techniques, such as focused ion beam (FIB) techniques, forms another part of this thesis. The focused ion beam milling technique was utilised for production of diamond probes which enabled push-out tests of individual glass microfibres to be carried out. Also, FIB cross-sectioning of indents induced by DSI test methods was performed. This novel research method showed large potential for a better interpretation of the test and an improved understanding of the microfracture processes in cement-based materials. Detailed information about FIB techniques is therefore presented in a separate chapter. The focus of this project has been to develop methods which will enable further systematic research into micromechanical properties of cementitious materials and may lead to the ultimate goal of this investigation - the development of a new generation of materials of improved macromechanical properties and durability.

published_or_final_version / Civil Engineering / Master / Master of Philosophy

published_or_final_version / Civil and Structural Engineering / Doctoral / Doctor of Philosophy

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This thesis deals with nonlinear analysis of reinforced concrete structures under monotonically increasing loads. Post-cracking behaviour of planar reinforced concrete structures is studied to investigate the tension stiffening phenomenon and the post-cracking shear resistance. The feasibility of using the available bond stress-slip relationships to model the steel-concrete interface behaviour is examined by incorporating these relationships in a three dimensional axisymmetric finite element model and analyzing several reinforced concrete tension specimens. / A finite element model which uses the advanced endochronic stress-strain relationship and incorporates the results of the investigation on post-cracking behaviour and steel-concrete interface behaviour is formulated and used in the analysis of several reinforced concrete members. Analysis results are compared with the available experimental data and with the results obtained by other researchers. Excellent correlation was obtained between the computed values and the experimental results.

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This thesis is a survey of the precast reinforced concrete skeleton system used in low-cost housing (SPCSS), which has widely spread to different areas of the world, but less studied. The thesis includes three major parts: (1) the development of SPCSS; (2) the design, performance feature of SPCSS; and (3) cases studies. / The development of SPCSS traces its origin as the structure of prefabricated houses for the housing shortage after the world war in Europe to its spread to developing countries for low-cost housing. / Design and performance study focuses on its features related to low-cost housing its special considerations and key points in design as a small component system, its acclaimed system performance features. / Case studies surveys 15 typical cases. Each case includes general background of the system, system design, comments following the design consideration and example of its application.

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