Resistance to acid, alkali, chloride, and carbonation in ternary blended high-volume mineral admixed concrete

The World Bank study predicts that 4°C warming will bring high temperatures, sea-level rise, and saltwater intrusion to India's southwest coast, damaging coastal concrete structures. Increased CO2 from industrialization exacerbates this, necessitating durable, low-carbon concrete. Combined use of fly ash (FA) and ground granulated blast furnace slag (GGBFS) as high-volume OPC replacements boosts performance while reducing concrete’s carbon footprint. In this perspective current study examines the durability of concrete against aggressive agents (H2SO4, MgSO4, NaCl, and CO2) causing premature deterioration of concrete structures along the southwest coast of India. Initially, three cost-effective sustainable concrete mix designs were developed, incorporating 50% replacement of OPC with locally available supplementary cementitious materials, specifically FA and GGBFS. These mixes were then evaluated for their mechanical and durability performances. The impact of aggressive ions (SO42-, Cl-, and CO32-) was studied by examining the changes in mechanical performance and phase assemblages. Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) techniques were used to estimate the phase compositions.
Ternary blended concrete having 50% OPC+ 30% GGBFS + 20% FA exhibited optimal synergistic performance, enhancing pozzolanic and hydraulic reactions for better resistance to harmful ions. The sorptivity test confirmed that as GGBFS content increased, the sorption rate decreased, indicating the higher reactive nature of GGBFS to that of FA. Deleterious compounds formed due to the action of SO42-, Cl-, and CO32- were identified to be ettringite (Ca6Al2(SO4)3(OH)12.32H2O, AFt) and gypsum (CaSO4.2H2O, Gy), Friedel’s salt (Ca4Al2(OH)12Cl2.4H2O, Fs) and polymorphs of calcium carbonate (CaCO3), respectively through TG mass loss curve. These results were corroborated by FTIR analysis, which showed predominant characteristic bands at 662 cm⁻¹ for SO₄²⁻, 459 cm⁻¹ for Mg–O stretching, 790 cm⁻¹ for Al–OH bending, and 1431-1443 cm⁻¹ for C–O, confirming the presence of the deleterious compounds.

This is an Accepted Manuscript of an article published by Taylor & Francis in Journal of Sustainable Cement-Based Materials on 25 Sept 2024, available at: https://doi.org/10.1080/21650373.2024.2405979.