Effects of Water-to-Binder Ratios (W/B) and Superplasticizer on Physicochemical, Microstructural, and Mechanical Evolution of Limestone Calcined Clay Cement (Lc3)

This study investigated the effects of water-to-binder ratios (w/b) and a commercial PCE-based superplasticizer on limestone calcined clay cement (LC3) performance. Zeta potentials, rheological characteristics, hydration kinetics, chemical, microstructural, and mechanical properties were assessed. A low w/b of 0.25 significantly reduced the hydration of the LC3. The admixture mainly relied on steric hindrance to improve the LC3 workability. The required admixture dosage was higher for LC3 than Portland cement, attributed to its intercalation into the layered structure of the calcined clay. The admixture presence slowed the early-age hydration, yet the resulting enhanced particle dispersion compensated the heat evolution at w/b of 0.25. LC3 reaction products were mainly characterized by C-(A-)S-H, portlandite, ettringite, monosulfate, and carboaluminates. Their morphologies at the low w/b were less apparent due to space confinement and associated constriction on crystal growth. Despite a higher mesopore content, LC3-based high-performance concrete attained a strength of more than 100 MPa.