Comparative performance of OPC and LC³-based composites under combined action of carbonation and chloride exposure

This study explored the performance of limestone calcined clay cement (LC³) and ordinary Portland cement (OPC) under the combined action of carbonation and chloride ingress. LC³-based paste and mortar were exposed to 20% CO₂ and 80% relative humidity at 30 °C. Corrosion mortar samples were also dried and wetted in 7.2% NaCl solution for 13 cycles. Both hydration and pozzolanic reaction products in LC³ were found to decompose at a faster rate. The decalcification due to carbonation altered its pore size distribution with a remarkable increase in pores < 3 nm. The pore-filling effect by the formed CaCO₃ improved the compressive strength and nanoindentation modulus of OPC, although no remarkable change was noted for LC³ due to its low Ca(OH)₂ content. Depassivation and active corrosion were noted in both binders, but the corrosion activity of LC³ surpassed that of OPC after Cycle 2.