Geometrical and boundary condition effects on restrained shrinkage behavior of UHPFRC slabs

Six large Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC) slabs were fabricated and tested to investigate the restrained shrinkage and cracking behaviors. The use of expanded polystyrene and Teflon sheets with two different slab thicknesses was considered to improve the shrinkage crack resistance. Free shrinkage was simultaneously measured to evaluate the degree of restraint according to the above test parameters. The test results showed that free shrinkage strains of –689 με to –723 με were obtained after 9 days, and prismatic specimens with a higher exposed surface area-to-volume ratio (S/V) had slightly higher free shrinkage strains than those with a lower S/V. Increasing the concrete slab thickness and using expanded polystyrene and Teflon sheets were effective at reducing the degree of restraint and improving the shrinkage crack resistance of the UHPFRC slabs. Among the various specimens, the slabs with the expanded polystyrene exhibited the lowest degree of restraint by 0.45 after 9 days.