Thermal and hydrothermal treatment of UHPC: influence of the process parameters on the phase composition of ultra-high performance concrete

Abstract Several studies show that thermal and hydrothermal treatment can further improve the excellent properties of UHPC in terms mechanical strength durability. While for increase is attributed to an intensified pozzolanic hydraulic reaction, previous accredited it mostly formation tobermorite. In presented study samples was systematically varied phase analysed related development a reference sample cured 28 days water. For results depends on protection against desiccation be ascribed improved reaction siliceous fillers. To achieve significant enhancement strength, pre-storage time few long dwell at elevated temperature/pressure are required. already heating specimens up 185 °C saturated steam followed by immediate cooling leads substantial compressive strength. Pre-storage did not affect result as far minimum several hours guaranteed. The performance due reaction. Surprisingly, tobermorite only found within very thin layer surface sample, but bulk. Sulphate aluminium stemming from decomposition ettringite bound newly formed phases hydroxylellestadite hydrogarnet.