Validation of slag-binder fiber-reinforced self-compacting concrete with slag aggregate under field conditions: Durability and real strength development

Abstract

The environmental conditions to which a concrete may be exposed will condition its real range of use. Thus, concrete behavior must, at all times, be verified under a wide variety of environmental conditions, in order to ensure its real applicability. In this study, the real strength development and durability behavior of a fiber-reinforced self-compacting concrete is analyzed. This particular concrete incorporates 100% coarse (4/12 mm) and fine (0/4 mm) Electric Arc Furnace Slag (EAFS) as aggregate, as well as limestone fines as aggregate powder (0/1.18 mm). Furthermore, Ground Granulated Blast Furnace Slag (GGBFS) was also added as binder. Four mixtures with and without either metallic or synthetic fibers, and different GGBFS contents were designed. Real strength development was evaluated in all the mixes by comparing the strength development of both cores extracted from full-scale beams and wet-cured laboratory specimens. The durability behavior was analyzed by Mercury Intrusion Porosimetry (MIP), freeze/thaw, moist/dry, sulfate-attack, chloride-penetration, carbonation, and SO2-attack tests. On the one hand, the long-term mechanical properties of the cores (real conditions) were similar to the properties of the specimens cured in a moist chamber for 90 days in all the mixes. On the other, the increase in water content when adding fibers to maintain flowability, as well as the addition of GGBFS, resulted in an increase in MIP porosity. Therefore, the use of fibers, both metallic and synthetic, slightly worsened the durability behavior of the concrete, facilitating the entry of aggressive external agents. Nevertheless, the increased flexibility of the cementitious matrix when adding GGBFS was beneficial against moist/dry and sulfate-attack phenomena, despite the increase in porosity. Overall, the mixes complied with the regulatory requirements for use in aggressive environments, although the amounts of fibers and GGBFS should be carefully studied.