Experimental investigation of the secondary creep of fiber reinforced concrete at high stress: Macroscopic measurement and digital image correlation

The secondary creep of Fiber-Reinforced Concrete (FRC) under high sustained stress levels is a key issue for structural durability when considering the capacity to guarantee small crack widths under serviceability states. This study investigates the time-dependent deformation of FRC beams under loading level Ps/P0 greater than 80% (Ps is the load at reloading and P0 is the load before unloading) with various aggregate sizes by using both the classical macroscopic measurement and the digital image correlation analysis (DIC). Notched beams made of FRC and Fiber Reinforced Mortar (FRM) (i.e. without aggregate) were firstly pre-cracked by static load and then applied by a loading equal to 80% of strength. The evolution of the deflection, the crack width, and the crack propagation were both measured by traditional sensors and calculated by DIC. Comparison between results from FRC and FRM materials highlights the influence of microstructure heterogeneity on the secondary creep of FRC. Moreover, the DIC analysis helps to get insights on the secondary creep mechanism.