Some Developments in Polypropylene Fibers for Concrete
Antoine E. Naaman, Surendra P. Shah,
and James L. Throne
Appears on pages(s):
bondina; costs: crack
flexural strength; g
lass fibers; metal
The main purpose of this project was to explore the feasibility of using newly developed polypropylene (PP) fibers as reinforcement for portland cement concrete and to compare their reinforcing effectiveness with asbestos, glass and steel fibers. The PP fibers used were made of a high tensile strength (up to 80 ksi), high modulus (up to lo6 psi), high stretch ratio (up to 12 to 1) polypropylene ribbon yarn supplied by AMOCO Synthetic Fabrics. The fibers were cut from a continuous strand obtained by properly twisting two PP ribbon yarns together. Twisting led to a substantial increase in the bonding properties of the fibers (mechanical bond) and their rigidity considered important during mixing. Different fabrication procedures and mortar mixes are described. Salient results of an extensive series of tests on flexural beams and pull-out tests to improve bonding properties are reported. Because steel, glass, asbestos and polypropylene have substantially different specific gravities, performance com-parison is made not only on the basis of volume fraction of fibers but also weight fraction and related costs. It stresses the potential merits of using PP or equivalent organic fibers in concrete matrices and suggests exciting research directions to pursue.