Effects of Arctic Low Temperatures and Freeze-Thaw Cycles on Mechanical Properties of Ultra-high Performance Concrete

Ultra-high performance concrete (UHPC) has a significant advantage in complex structures relevant to Arctic environment conditions such as long-span bridges and offshore platforms due to its high strength, high toughness and excellent durability. To explore the compressive response of UHPC at low temperatures and after freeze-thaw cycles, two series tests were conducted. Firstly, the compressive strength of UHPC exposed to low temperatures was experimentally investigated. The UHPC cubes had good integrity after failure due to the bridging effect of continuous steel fibers. The compressive strength of UHPC increased almost linearly with reducing temperature in the range of 20–80 ℃. Then, a total of 17 groups of UHPC and NWC cubes were prepared to explore the compressive response of UHPC after freeze-thaw cycles. The investigated parameters include freezing temperature (−30, −60, and −80 ℃) and number of freeze-thaw cycles (25, 50, 75, and 100). With the increase of number of freeze-thaw cycles and the decrease of freezing temperature, the degradation in compressive strength of UHPC gradually became distinguished. Finally, the regression analysis was conducted to establish the empirical formulae for the compressive strength of UHPC at different low temperatures and after freeze-thaw cycles. The accuracy of the developed formulae was validated by the experimental results.