Improvement in early-age cracking performance of concrete with hybrid steel-macropolypropylene fiber blends

Cracking in concrete occurs at an early age due to volumetric changes in the material produced by environmental effects or internal mechanisms. The cracks developed at an early age adversely affect the durability and long-term performance of concrete. Cracks permit penetration of deleterious liquids and gases into concrete which seriously compromise the structural integrity, durability, and service life of the structure. In this paper, the early-age fracture response of concrete with steel (SF050) and hybrid blend of steel and macropolypropylene fibers (Hy050) is evaluated and related with the observed plastic shrinkage cracking. An improved performance is achieved from the hybrid blend with a smaller dosage of steel fibers when used in combination with macropolypropylene fibers. The cohesive stress-crack separation (σ-w) relationship obtained from the fracture tests indicate a higher residual stress at a smaller crack separation in Hy050 when compared with SF050. The synergistic effect of hybrid blend results in significant reduction in plastic shrinkage cracking and cracking density. © 202