This thesis looks into the behaviour of reactive powder concrete (RPC) when subjected to high temperature. It is divided into two parts. The first part reports the experimental programme involving testing of RPC mixes containing hybrid steel-PVA fibres after exposure to high temperature. A mix was selected as optimum based on its performance at high temperatures. Further tests were conducted on that mix at the hot state. The second part of the thesis is development of a hygro-thermal model for RPC. In the experimental program, six RPC mixes containing different volume fractions of hybrid steel-PVA fibres have been studied under temperatures of up to 700ºC. The behaviour was studied through material property tests; such as compressive strength and static elastic modulus and material property tests such as ultra sonic pulse measurement and mass loss tests. It was found that the RPC containing equal amount of steel and PVA fibres occupying a total volume fraction of 2% behaves better in terms of both mechanical properties and resistance to explosive spalling. Further, tests have been conducted for the selected mix at the hot temperature, for this purpose a furnace-loading frame assembly was fabricated that is capable of simultaneous heating and loading of the specimens. Elastic modulus and axial thermal strains and transient creep were measured for the selected mix at high temperatures under different load levels.In the second part of the thesis, a hydro-thermal model for RPC is presented. The model has a three degrees of freedom and it is capable of predicting the temperature histories and pore pressure development inside 1-D RPC elements when subjected to high temperature. Constitutive relationships were developed that may be used for the modelling of ultra high performance concretes (UHPC). Influence of different constitutive relationships and material relationships on the results predicted by the model were studied and the model was used to study RPC cylinders when subjected to high temperature.
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