Utilization of a diatomaceous earth by-product as a supplementary cementitious material: Hydration behavior, strength development and environmental efficiency

This study investigates the reuse of an industrial by-product generated during the pneumatic classification of diatomaceous earth (DE), collected from baghouse filters, as a supplementary cementitious material partially replacing Portland cement at levels of 10%, 20%, 30%, and 40% by mass. Hydration kinetics, pozzolanic reactivity, and compressive strength of cement pastes were evaluated at curing ages of 7, 28, and 91 days. The results indicated that DE promoted accelerated early hydration through filler and nucleation effects, followed by significant portlandite consumption at later ages, confirming its pozzolanic activity. In the absence of dispersant, a reduction in compressive strength was observed due to increased porosity. However, at 91 days, pastes containing up to 20% DE exhibited compressive strength statistically equivalent to that of the reference paste. The use of a polycarboxylate-based superplasticizer significantly improved particle dispersion, reducing porosity by up to 41.6% and increasing compressive strength by up to 2.34 times in the paste containing 40% DE when compared to the same composition without superplasticizing admixture. Furthermore, DE incorporation reduced binder intensity and CO 2 intensity by up to 40% relative to the reference cement paste, demonstrating enhanced environmental efficiency of the system.