Microstructural characteristics of ultra-high performance concrete by grid nanoindentation and statistical analysis
In this study, grid nanoindentation and statistical deconvolution analysis were applied into a developed Ultra-high performance concrete (UHPC) to broaden the understanding of the microstructure phases and their mechanical properties. A total of 550 nanoindentation tests was carried out on UHPC and the mechanical properties, including indentation modulus and hardness of the indented material were extracted from nanoindentation load-depth curves. The statistical deconvolution analysis was then utilized to analyze the modulus and hardness spectra. The experimental and analysis results revealed that the modulus and hardness data obtained from nanoindentation tests can be used in the accurate and reliable identification of the microstructure phases and their properties in UHPC. For the present UHPC, the microstructure can be characterized into 6 phases with distinguishable mechanical properties, including micro porosity, Low Density Calcium Silicate Hydrates (LD CSH), High Density Calcium Silicate Hydrates (HD CSH), silica powder and sand, and residual cement clinker. The obtained modulus and hardness values of these phases were in the range of various reported ones for cement-based materials and UHPC.
ultra-high performance concrete; microstructures; micromechanical properties; nanoindentation; statistical analysis.
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