A Comparative Investigation of the Performance of Natural and Synthetic Fibers in Pavement-Quality Concrete

Concrete pavements are susceptible to early-age plastic shrinkage cracks (PSC), compromising their durability and escalating maintenance costs. Micropolypropylene synthetic fibers have been proven to arrest PSC effectively. However, using synthetic fibers may have implications on the economical and sustainability aspects of roads. The present study evaluated the efficacy of the discarded coconut fibers (coir) in arresting the PSC. Also, the influence of incorporating coir on the mechanical behavior of conventional and steel fiber-reinforced concrete systems was investigated and compared with synthetic fiber-reinforced paving concrete. It was found that coir fibers could completely arrest the PSC at 0.3% dosage (by concrete volume), whereas 0.4% synthetic fibers were required to mitigate PSC. This was due to a 27% rougher surface texture of coir compared to synthetic fibers. Similarly, the coir fibers could reduce the cumulative bleeding in concrete by 45% compared to conventional paving concrete. Although coir fiber-reinforced paving concrete exhibited 10% lower compressive strength than synthetic fiber systems, it demonstrated >10% higher toughness. Likewise, incorporating coir in steel fiber paving concrete increased the toughness by 135% and abrasion resistance by 17% compared to conventional paving concrete. These results indicated that coir fibers could completely replace synthetic fibers in paving-concrete construction without much affecting their durability and serviceability.