Corrosion Assessment of Sustainable Foam Concretes Incorporating Binder and Filler Modification with Slag and Fly Ash

The corrosion assessment of sustainable foam concretes (FCs) developed by coupling the approach of using high volumes of poorly reactive fly ash (FA) and high volumes of ground granulated blast furnace slag (GGBS) as a sand and cement blend, respectively, has been explored. Because FCs have higher macropores, their use for reinforced concrete (RC) applications is often restricted from a corrosion perspective, wherein improved chloride ion transport properties are crucial. In the present study, five GGBS-FA combinations in FCs were produced and investigated for their corrosion performance using resistivity, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) method, and scanning electron microscopy (SEM). Results suggest that most FCs with GGBS-FA combinations improved the chloride ion permeation significantly, demonstrated comparable or superior passive film formation, and prolonged the corrosion initiation cycle by 2-4. Specifically, increased Rct and larger negative phase angles in the low-frequency ranges (indicating a higher capacitive property) in the steel rebar region have enhanced the passive film stability, thereby reducing the likelihood of active corrosion. Different tests conducted for the assessment of corrosion initiation supported each other well and proved to be reliable for assessing the behavior of specimens having different resistivities. Corrosion-induced cracks were identified in FC specimens using SEM images, elemental mapping, and visual observations. Last, these mixtures reduced CO2 emissions and production costs by 22.2%–47.8% and 11.9%–24.2%, respectively. With the individual effects of GGBS and FA influencing the corrosion behavior of FCs positively, the study provides clear-cut evidence about the employment of the combined strategy as a viable alternative for FC to be used in RC applications. Additionally, with such materials present at high volumes, the low CO2 emissions and cost-effective aspects can be met, providing a highly sustainable option.