Short-Term Efficiency of Using Sustainable BFRP Bars in Post-Tensioning Systems for One-Way RC Slab

Abstract

Basalt Fiber Reinforced Polymer (BFRP) bars are manufactured from sustainable natural materials. BFRP Young’s modulus constitutes weak performance to the serviceability limits in the structural reinforced concrete (RC) elements, but using post-tensioning systems controls the serviceability limits. Nine RC slabs were tested under a four-point bending scheme. However, the efficiency of using the BFRP post-tensioning system bars as a main reinforcement of RC slabs was evaluated in two different stress levels of 10% and 50% of the rupture strength of the bars. The near-surface mounted (NSM) external strengthening post-tensioning BFRP system by two different stress levels of 10% and 30% of the rupture strength was investigated. Additionally, the hybrid reinforcement performance of both steel and BFRP bars was studied. The relevant results showed that the post-tensioning BFRP systems significantly enhanced the ultimate load and vertical deflection of the RC slabs if the stress level was 50% and 30% for the internally reinforced and externally strengthened slabs, respectively. BFRP bars in hybrid RC slabs achieved more energy absorption. At the same reinforcement area, the internal bonded BFRP bars can achieve a higher ultimate load than the unbonded external BFRP bars by 11%. Furthermore, the increment rate in prestressing losses for RC slabs with higher prestressing levels of BFRP bars was less than that of slabs with lower prestressing levels of BFRP bars. Consequently, the efficiency of the external post-tensioning system was 95.78% for the RC slab with a 50% stress level after 1000 hrs, and it’s recommended as a design guideline.