Influence of low curing temperatures on the tensile response of low clinker strain hardening UHPFRC under full restraint

The tensile response of strain hardening UHPFRC under full restraint, subjected to curing temperatures of 20 degrees C, 10 degrees C, 5 degrees C, was investigated for two types of mixes with silica fume; Mix I with pure type I cement and Mix II with 50% replacement of cement with limestone filler, both having a similar steel fibrous mix. The development of the elastic modulus, tensile strength, autogenous shrinkage and eigenstresses were put into perspective with the hydration kinetics. Two phases of pozzolanic reaction with different rates of consumption of silica fume were identified. A systematic increase of the autogenous shrinkage and eigenstresses with the curing temperatures was observed. The eigenstresses development was much slower in the case of Mix II, owing to its larger relaxation potential. The eigenstresses in Mix I reached the strain hardening domain after one month, whereas the same in Mix II were only approaching the strain hardening domain after three months.