Enhancing corrosion resistance of reinforced high-performance concrete with 100% steel slag aggregate replacement using a hybrid fly ash and ground granulated blast-furnace slag

Abstract

The use of steel slag aggregate (SSA) in reinforced concrete is a promising approach for reducing natural aggregate consumption and promoting sustainable construction. However, the porous structure and electrical conductivity of SSA may adversely affect chloride transport and reinforcement corrosion resistance. This study investigates the effects of fly ash (FA) and ground granulated blast-furnace slag (GGBS) on the durability performance of reinforced high-performance concrete incorporating 100% SSA as coarse aggregate replacement. Five concrete mixtures with a constant water-to-binder ratio of 0.32 were prepared, including a reference concrete and SSA concretes containing 15% FA, 35% GGBS, and a hybrid 15% FA–35% GGBS binder system. The influences of FA and GGBS on porosity, water absorption, chloride ion penetrability, alkalinity, and accelerated corrosion behavior were experimentally evaluated. The results showed that full replacement of natural coarse aggregate by SSA increased porosity and water absorption while maintaining compressive strength comparable to that of the reference concrete because of the high stiffness and rough surface texture of SSA. However, the plain SSA concrete exhibited the shortest corrosion-cracking initiation time because its porous structure facilitated moisture and chloride transport. The incorporation of FA and especially GGBS improved the corrosion resistance of SSA concrete, as reflected by lower water absorption and longer corrosion-cracking initiation times. These trends were consistent with reduced accessibility and connectivity of transport pathways in the cementitious matrix. The hybrid FA–GGBS system exhibited the best overall durability performance, with the lowest charge-passed value and the longest corrosion-cracking initiation time. The findings also indicate that rapid chloride penetration test results alone may not fully represent the durability performance of SSA concrete because the electrical conductivity of SSA can influence the measured charge-passed values. Overall, within the investigated materials and testing conditions, the incorporation of FA and GGBS mitigated the chloride-related durability limitations associated with the porous SSA used.