Influence of hybrid fibers on the fresh and hardened properties of silica fume blended concrete

¹ Department of Civil Engineering, Vignana Bharathi Institute of Technology, Hyderabad, Telangana, 501301, India
² Department of Civil Engineering, Geetanjali College of Engineering and Technology, Hyderabad, Telangana, 501301, India
³ Department of Civil Engineering, Vardhaman College of Engineering, Hyderabad, Telangana, 501218, India

^* Corresponding author: mounikareddy92@gmail.com

Published online: 7 January 2026

Abstract

This research explores impact of hybrid steel (ST) and polypropylene (PP) fibers on both fresh and hardened behavior of 10% silica fume (SF) blended M30 concrete. Hybrid fibers are introduced at dosages of 0%, 0.5%, 1.0%, 1.5%, and 2.0% total volume (equal proportions of ST and PP). As the fiber dosage increased, the slump declined from 132 mm (control) to 34 mm (2.0% hybrid fiber), reflecting decreased workability. The initial and final setting times increased from 3 h 15 min and 5 h 20 min (control) to 5 h 30 min and 7 h 50 min (2.0% hybrid fiber). The 28-day compressive strength augmented to a maximum of 49.5 MPa at 1.0% hybrid fiber compared to 39 MPa for the control sample. However, the flexural strength increased from 4.3 MPa to a highest of 6.5 MPa at 1.0% hybrid fiber. Increasing the fiber dosage increased fiber balling, contributing to less strength due to poor packing. Therefore, the optimal hybrid fiber dosage is determined to be 1.0% by volume (0.5% ST + 0.5% PP) because this dosage provides the best mechanical performance, crack resistance, and acceptable fresh properties. This configuration provides good post-crack performance as well as acceptable workability and setting times for structural applications.