Experimental Research on the Flexural Performance of Ultra-High Performance Concrete Slabs with Different Types of Fibers

Ultra-High-Performance Concrete （UHPC） demonstrates significant application potential in civil engineering due to its excellent mechanical properties and durability. However， the synergistic mechanisms between fiber type and member size—key influencing factors for its flexural performance—are not yet fully understood. Existing research often focuses on single variables， lacking systematic investigation into the interactive effects of slab thickness and different fiber types. This paper presents a comparative experimental study on a total of six slabs， with research parameters including fiber type ［steel fiber， glass fiber， polyoxymethylene （POM） fiber］ and slab thickness （30 mm， 50 mm）. The test results indicated that slab thickness had a significant influence on flexural performance. Increasing the thickness from 30 mm to 50 mm enhanced the cracking load and ultimate bearing capacity by 3 to 4 times. Under the same thickness conditions， the reinforcement effects of different fibers varied markedly： specimens with steel fibers exhibited the highest bearing capacity， followed by those with glass fibers， while POM fiber specimens showed the lowest capacity. When the slab thickness increased from 30 mm to 50 mm， the ductility of the steel-fiber， glass-fiber， and POM-fiber specimens improved by 37.4%， 3.4%， and 13.0%， respectively. Strain analysis revealed that the plane-section assumption held before cracking and up to approximately 60% of the peak load. Beyond this threshold， nonlinear characteristics emerged， varying with fiber type and slab thickness.