Aspects of micromechanical properties of cement-based materials.
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
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.