Abstract: The enhancing of flexural strength provided from using Polyvinyl Alcohol (PVA) as internal curing in concrete mix will be studied in this researcher. PVA constitute an adhesive gel attached concrete components. Thickness of concrete layer which modified with PVA was the first variable of this research (25 and 50% of total thickness of slab). Also, the comparison between solid slab and bubble slab was considered the second variable of this study. The linear load was applied on two lines perpendicular on supports. The slabs were supported by two opposite simple support. The results were obtained by testing six slabs (87×87×6 cm) of 70 cm supported length and measuring the maximum load and mid span deflection. PVA increased the load capacity of 47.4 and 55.6% and decreased the maximum deflection of 28.6 and 50.3% for solid slabs while PVA increased the load capacity of 34.7 and 35.6% and decreased the maximum deflection of 18.6 and 25.7% for bubble slabs.