EFFECT OF MORTAR FINENESS AND ADHESIVE AGENTS ON PULLOUT RESPONSE OF STEEL FIBERS

The influence of mortar fineness and several adhesive additives on the pullout load versus slip response of steel fibers is described. Ten different mortar mixtures were prepared. Parameters included two types of sand and four types of additives that were expected to influence the interfacial zone between the fiber and the matrix. The fibers were either smooth round, hooked round, or triangular twisted. All mixtures had the same sand-to-cement ratio and water-to-cementitious ratio. The two sands were Ottawa silica sands: one identified as normal sand 50-70 (passing American Society of Testing and Materials sieve 50 and retained on sieve 70, with an average particle size 270 microns) and the other identified as microsand 270 (with an average particle size of approximately 14 microns). The four additives were fly ash (as a cement replacement), metakaolin, latex, and polyvinyl-alcohol. Control mixtures without any additive were also tested. The specimens prepared were half dogbone-shaped specimens with a single embedded fiber. At least four specimens were prepared and tested for each parameter. Pullout load versus global slip curves were recorded, and an average curve was generated for comparison purposes. Conclusions were drawn related to the influence of test parameters on the pullout load versus slip response; frictional, adhesive or mechanical bond; and pullout energy.