Corrosion performance and strain behavior of reinforced concrete: Effect of natural pozzolan as partial substitute for microsilica in concrete mixtures

Abstract

Reinforced-concrete structures in southern Iran are susceptible to chloride-ion-induced corrosion, thus necessitating measures to reduce concrete permeability and protect embedded steel reinforcements. Microsilica is conventionally added at a cement weight of 8 % to enhance durability. In a recent investigation, the authors developed an innovative concrete mix design that replaces microsilica with natural pozzolan while ensuring compliance with the stringent durability and strength requirements stipulated by the construction industry. The current study advances the abovementioned investigation by precisely examining the corrosion performance of steel reinforcements in concrete beams constructed using eight mix designs proposed earlier. Sixteen beams are prepared and subjected to 60 d of accelerated corrosion using 5 % sodium-chloride solution and an impressed current to mimic harsh environments. Transverse strains are recorded every 10 d to assess deformation related to reinforcement corrosion. Subsequently, the beams are deconstructed to measure the rebar corrosion rates. The results indicate that the mix design containing 4 % microsilica and 12.5 % pozzolan exhibit corrosion levels almost identical to those of the control mix with 8 % microsilica, i.e., 8.9 % and 8.1 %, respectively. Further analysis shows a clear relationship between the transverse strain and the corrosion rate, with higher corrosion resulting in greater strain. Mixes containing more than 25 % pozzolan content experience significant bidirectional transverse strains, which is attributable to the accumulation of internal pressure inside the beam due to corrosion products.