Cementitious composites with polypropylene fibers: evaluations in the fresh and hardened state

ABSTRACT

The concrete is a material widely used worldwide. Some of its particularities are cracking and low tensile strength. Thus, the addition of fibers can be a viable alternative, in order to minimize the occurrence of these effects. The present study has investigated the advantages and disadvantages of the addition of polypropylene fibers in cementitious materials and, finally, presented the results and considerations of an experimental study on the properties of microconcrete composites in the fresh and hardened state. Two types of fibers were used: a short one 12 mm long (microfibers), and another one 54 mm (macrofibers). The fiber content, in relation to the microconcrete volume, was 0.1%, 0.2%, 0.3% and 0.4% for microfiber, and 0.3%, 0.4% and 0,5% for macrofiber and hybrids. The latter were composed of 30% microfibers and 70% macrofibers. Part of the cement was replaced by silica fume (SF) and fly ash (FA), in the proportions of 7.5% for each one, by weight. The binder: aggregate ratio was 1:3 by weight. For aggregates, the ratio of 30% natural sand and 70% artificial sand, by weight, was adopted. As for the effect of the microfibers, they presented satisfactory results for additions of 0.1% in the composite with the addition of microfibers and in all the hybrid compositions at the ages of 28 and 91 days, both in the fresh and in the hardened state. As for the macrofibers, they caused a slight reduction in the slump and absorption, consistency in the percentage of trapped air and improvement in the results in the hardened state for the contents of 0.4% and 0.5%, in relation to the reference mixture (without fibers ).

Keywords
Microconcrete; Cementitious composite; Microfibers; Macrofibers; Polypropylene