Behavior of Limestone Calcined Clay (LC3) Columns under Axial Loading

Abstract

The cement industry is a major contributor to global CO₂ emissions, largely due to the high clinker content of Ordinary Portland Cement (OPC). Limestone Calcined Clay Cement (LC3) has emerged as a promising low-carbon alternative, but its structural performance in reinforced concrete (RC) columns is not yet well established. This study experimentally investigates the behavior of RC columns made with LC3-50, in which 50% of the clinker is replaced by a blend of calcined clay and limestone, under axial compressive loading. Six square columns (150 × 150 × 900 mm) and companion cylindrical specimens were cast with either OPC or LC3-50 concrete and tested for 28-day compressive strength, axial load–carrying capacity, stiffness, deformation, and crack patterns. The LC3-50 concrete achieved a higher 28-day compressive strength (51.6 MPa) than OPC (44 MPa), and the LC3-50 columns exhibited an approximately 15.7% increase in ultimate axial load capacity (66.15 tons versus 57.20 tons for OPC), along with greater deformation capacity (9.65 mm versus 8.23 mm). LC3-50 columns primarily failed by material crushing, while OPC columns showed more pronounced bonding failures and earlier crack initiation. These results indicate that LC3-50 not only reduces clinker content and associated CO₂ emissions but also enhances the axial performance and ductility of RC columns, supporting its use as a sustainable alternative to conventional OPC in structural applications.