Tensile Properties of Portland Cement Reinforced with Kevlar Fibers

Abstract

Composite specimens for tensile testing were made from various amounts of Kevlar fibers in Portland cement. Testing revealed about 50% improvement in the Elastic Modulus and yield strength over the unreinforced cement. The maximum amount of fibers, which was possible to add without destroying the continuity of the cement matrix, was about 2%. Specimens containing less than about 0.15% of fibers failed in a brittle manner like a single phase material. Specimens containing more than that amount of fibers displayed multiple fractures of the matrix before the final failure. The ultimate tensile strength started to improve at the critical volume of fibers equal to 0.3% and not as predicted theoretically at 0.75 % . The most dramatic improvement in the properties of cement was in the Energy to Fracture. This increased almost two orders of magnitude with 1.96% of fibers by volume.