Fine aggregate substitution with acidified granular activated carbon influences fresh-state and mechanical properties of ordinary Portland cement mortars

The compressive strength and selected fresh-state responses to incorporating acid-modified granular activated carbon (GAC) in cement mortars, were compared to physical cement behaviors associated with the incorporation of otherwise unmodified GAC and a commercial polycarboxylate superplasticizer. Specific surface area of unmodified and acidified GAC, porosity, pH at charge neutrality (pH _PZC ), and surface-associated functional groups were compared. Fresh- and hardened-state responses were observed, including slump, setting time, zeta potential, and compressive strength. Results suggest that substituting 1% of the fine aggregate mass with GAC particles that had been pre-treated in nitric acid, can improve compressive strength and workability of cement mortar.