Effects of ambient temperature and shrinkage on early-age UHPFRC samples

Ultra-High Performance Fibre Reinforced Concrete (UHPFRC) is generating great interest worldwide due to its superior mechanical properties and durability. Evaluating the strain behaviour as a result of environmental conditions is relevant in order to insure good performance in this material. The strain produced in square samples with thicknesses of 40, 70, and 150 mm of UHPFRC and conventional concrete (CC) with a thickness of 150 mm while exposed to environmental conditions of Bogotá (Colombia) were researched in this study. The difference in the thermal expansion coefficient (TEC) between the UHPFRC and the CC was determined for different cures ages. Furthermore, the impact of relative humidity (RH) on the initial contraction of the UHPFRC was identified under controlled conditions of 20 (Formula presented.) C. Temperature values measured on the upper and lower face of the sample with a thickness of 40 mm were greater than those of other evaluated thicknesses. The results indicated a higher strain differential measured in the upper face for the UHPFRC samples. In regards to CC, a different situation was observed for the lower face temperature differential. In conclusion, strain behaviour of the 70 mm and 150 mm samples is affected by temperature differentials, whereas for the 40 mm thick plate it is affected by RH.