Effect of fiber volume factor incorporated in cement-based composites with and without mineral additions.

Reference	Presenter	Authors (Institution)	Abstract
04-017	Felipe Sérgio Bastos Jorge	Jorge, F.B.(Centro Federal de Educação Tecnológica); Rodrigues, C.S.(Centro Federal de Educação Tecnológica);	Use of steel fibers in cement-based composites has become popular due to possibility of using that material as total or partial replacement of conventional reinforcement, as in floor slabs or tunnel cover. This reinforcement aims at improving composites properties with regard, mainly, to cracks propagation. It’s known that concrete has high compressive strength and durability, but its toughness is low, being considered a fragile material. The performance of the fiber as stress bridge depends on several factors, among them bond strength between fiber and matrix. Interfacial Transition Zone (ITZ) is one in which first cracks that lead to material failure appear. Some researches with mineral additives, such as rice husk ash (RHA), are aimed at ITZ densification. RHA has a high content of amorphous silica, which gives it high potential for its pozzolanic activity. That RHA characteristic is able to potentiate new hydration products formation, especially C-S-H, giving a higher density to cement matrix and pores and voids reduction. Research’s aim is to evaluate incorporated fiber volume factor in concrete in relation to toughness gain in composites without RHA addition and 15% replacement of cement by RHA. For that, concrete samples were produced without addition of RHA with fiber percentages of 0.5, 0.75 and 1.0% by volume, with 15% RHA and fiber percentages of 0.5, 0.75 and 1.0% by volume, in addition to control samples. Flexural tests were carried out at four points with controlled deformation and electronic displacement control device. Through the results found it is possible to establish suitable volume of fibers incorporated. It was also possible to conclude that RHA replacement of cement is an alternative to reduce part of impact caused by use of cement without performance loss.
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