Dispersion and effects of metal impregnated granular activated carbon particles on the hydration of antimicrobial mortars

Abstract

Granular activated carbon (GAC) particles impregnated with antimicrobial metals were incorporated into cementitious materials for the express purpose of inhibiting biogenic concrete corrosion. We report herein the influence of such metal-laden GAC particles on the hydration of cement mortars when substituted for fine aggregate, as well as the dispersion of metal in the cured matrix. Isothermal calorimetry was utilized to study the influence of GAC without and with copper and/or cobalt on select hydration characteristics of ordinary portland cement (OPC) mortars. When 1% of the fine aggregate mass was replaced with GAC particles of similar size, total evolved heat in all formulations was similar, regardless of GAC pretreatment. However, as the substitution approached 10% of the fine aggregate mass, metal-laden GAC formulations imparted delays in heat liberation and lowered heat fluxes. Results also substantiate that metal-laden GAC particles participate in the enhanced uptake of the calcium that is normally liberated during cement mixing and that the water delivered with GAC particles is not readily available during the first 142 h of curing. Electron microprobe analysis (EMPA) elucidated that copper and cobalt were homogenously distributed throughout the cement paste with metal-laden GAC, with these metals concentrations localized in a 50–100 μm region surrounding the GAC particles. Compressive strengths were not affected by the presence of metal-impregnated GAC in the concentration ranges tested and reported herein.