DURABILITY ASSESSMENT OF RECYCLED TIRE STEEL AND NYLON HYBRID FIBER-REINFORCED CONCRETE MODIFIED WITH NANO-ZrO₂ FOR RIGID PAVEMENT APPLICATIONS

Excessive mechanical and environmental stresses frequently cause rigid pavements to deteriorate more quickly, resulting in early cracking, moisture intrusion, and a shorter service life. For sustainable rigid pavement applications, this study examines how adding Nano-ZrO₂ to Recycled Hybrid Fiber-Reinforced Concrete (RHFRC) can increase its durability. In order to create seven concrete mixes, 0.2% Nano-ZrO₂ was combined with recycled tire steel fibers (RTSF) and recycled nylon fibers (RNF) in various hybrid ratios. According to the applicable ASTM and ACI standards, durability was assessed using tests for water absorption, freeze-thaw resistance, impact energy absorption, ultrasonic pulse velocity (UPV), and drying shrinkage. The results showed that adding RTSF and Nano-ZrO₂ together greatly improved frost durability and decreased permeability (by more than 20%). After 200 freeze-thaw cycles, the RTSF1.5 + 0RNF mix maintained 94% of its compressive strength. In comparison to the control mix, impact resistance more than seven times increased, and improved internal integrity was indicated by UPV values (3.8–4.35 km/s). At 180 days, hybrid mixes with a moderate amount of nylon (RTSF1 + RNF0.5) successfully reduced drying shrinkage by 20%. In order to create a more resilient and sustainable pavement concrete, recycled fibers and Nano-ZrO₂ worked in concert to refine the microstructure, increase durability, and limit microcracking.