Mechanical Properties and Durability of Limestone Calcined Clay Cement (LC3) in Engineered Cementitious Composites LC3-ECC with steel fibers

Abstract This study investigates the mechanical properties and durability of Limestone Calcined Clay Cement (LC³) in Engineered Cementitious Composites (LC³-ECC) reinforced with steel fibers, with contents varying from 0 to 2% by volume. The dynamic elastic modulus of the composites was determined using ultrasound and acoustic tests (Sonelastic), and a correlation between both tests was proposed. A 3-point bending test was conducted to determine the flexural strength, toughness, resilience, and ductility of the LC³-ECC. The compressive strength at 7 and 28 days was also evaluated. Finally, a durability test through chloride migration and a simplified carbon dioxide (CO₂) emissions analysis was performed. Incorporating 2.0% fiber content resulted in increases of 40% in flexural strength, 1270% in toughness, 243% in resilience, and 166% in ductility. This demonstrates the ability of LC³-ECC to withstand strain under load without failure and to maintain residual stresses in the post-peak phase. The calculation of CO₂ emissions indicated that incorporating fibers at percentages up to 2.0% increased the eco-efficiency to 7.89 MPa/kg CO₂ compared to 6.78 MPa/kg CO₂ for the composites without fibers in terms of flexural strength. Therefore, the study highlights that steel fibers balance between improving mechanical performance and minimizing environmental impact, particularly in the optimal 2% fiber mix that combines robust structural benefits with a manageable environmental footprint.