Influence of Hydrothermal Curing on Micro Structure and Mechanical Properties of Ultra-High-Performance Concrete

Abstract

Abstract: Several studies show that hydrothermal treatment can further improve the excellent properties of UHPC in terms of mechanical strength and durability. The hydrothermal treatment previous studies accredited it mostly to the formation of tobermorite. In the presented study hydrothermal treatment of UHPC samples was systematically varied and thephase formation analysed related to the strength development of a reference sample cured for 28 days in water. For the hydrothermal treatment already heating the specimens up to 185 °C in saturated steam followed by an immediate-cooling leads to a substantial increase in compressive strength. Pre-storage time did not affect the result as far as a minimum of several hours is guaranteed. The improved performance is due to an increase in the pozzolanic and hydraulic reaction. Surprisingly, tobermorite was only found within a very thin layer at the surface of the sample, but not in the bulk. Sulphate and aluminium stemming from the decomposition of the ettringite are bound in the newly formed phases hydroxylellestadite and hydrogarnet