The tensile behavior under low loading rates governs to a large extend the mechanical response of Strain Hardening Ultra High Performance Fiber Reinforced Concretes (SH-UHPFRC) at early age and long term, in applications of rehabilitation. A viscoelastic-viscohardening model was developed and applied to predict the tensile response of two types of SH-UHPFRC; Mix I with pure type I cement, silica fume and steel fibers and Mix II with 50% replacement of cement with limestone filler and a similar fibrous mix, and compare their time dependent performance. Different tensile loading conditions were investigated, including the behavior under restrained shrinkage deformations, the effect of very low monotonic strain rates, and linear and non-linear relaxation and creep tests. The predictions of the model were also compared with experimental results from literature. The interaction of ageing, hydration, early age volume changes, viscoelastic phenomena and damage and their influence on the overall tensile behavior of UHPFRC was discussed.