Ultra-high-performance fiber-reinforced concrete: Shrinkage strain development at early ages and potential for cracking

This study investigates the effects of the concrete-ring thickness and steel fiber on the restrained shrinkage behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) using the ring test. To do this, three different concrete-ring thicknesses (t_c=20, 30, and 40 mm) and two different fiber contents (V_f=0 % and 2 %) were considered. The test results indicated that the ring specimen without fiber exhibited shrinkage cracking after nearly 1.4 days because of its low tensile strength, whereas no shrinkage cracking was observed for the ring specimens with fibers during testing. A thicker concrete ring provided lower residual stress, relaxed stress, degree of restraint, and cracking potential. Therefore, it was concluded that using steel fiber and increasing the concrete thickness perpendicular to the tensile stress direction can improve the shrinkage cracking resistance of UHPFRC.