Effect of normal and PCE-Modified C-S-H seeds on cement paste properties: A statistical approach using local polynomial regression and functional ANOVA

Calcium silicate hydrate (C-S-H) seeds have emerged as a viable option for accelerators in concrete. The study investigates influence of synthetic C-S-H nanoparticles, unmodified (Normal_CSH) and polycarboxylate ether-modified (PCE_CSH), on setting behaviour, workability, strength development, and shrinkage characteristics of cementitious systems. Rice husk ash and carbide slag, two industrial waste materials, are used as sources of silicon and calcium for synthesis of C-S-H. Local Polynomial Regression and Functional ANOVA employed to statistically model and interpret effects of C-S-H. Compressive strength at 1, 3, 7, 28 days showed that both C-S-H types improve early-age strength, with peak gains up to 79 % at 2 % PCE_CSH. Optimal strength performance occurred within 1.3 %–2.5 % dosage, beyond which agglomeration effects limited further gains. Increased early-age shrinkage was observed, attributed to accelerated hydration, microstructural densification, and internal self-desiccation. The study establishes C-S-H, particularly PCE-modified form, as a promising additive for enhancing early performance in cement-based materials.