Silica Fume Concrete: A Solution to Steel Reinforcement Corrosion in Concrete

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Title: Silica Fume Concrete: A Solution to Steel Reinforcement Corrosion in Concrete

Author(s): John T. Wolsiefer

Publication: Special Publication

Volume: 126

Issue:

Appears on pages(s): 527-558

Keywords: chlorides; corrosion; durability; electrical resistance; permeability; silica fume; Materials Research

Date: 8/1/1991

Abstract:
Discusses the utilization of silica fume concrete admixture to prevent reinforcing steel corrosion. The mechanism of steel corrosion in salt-impregnated concrete is described, along with laboratory test date showing how ordinary concrete's corrosion-prone characteristics are altered by the use of silica fume. The mineral admixture significantly lowers the concrete permeability to prevent chloride ingress to the reinforcing steel level, while simultaneously increasing the concrete's electrical resistance to corrosion currents. Test data from the FHWA 90 day Chloride Ponding Test indicates a 98 percent reduction in chloride penetration. The AASHTO T277 rapid chloride permeability test shows a 10-times impermeability and 25-times resistivity improvement with the use of 12 percent silica fume. T he Time-to-Corrosion FHWA/NCHRP 244 slab test is scaled-down steel-reinforced deck, from which macrocell corrosion current, AC resistance, half-cell potential, and chloride absorption are measured. Zero corrosion current was measured after NaCl was ponded in alternate soak/dry cycles for 48 weeks. The second phase test program evaluated the corrosion performance of full-sized concrete bridge sections, including beams, columns, piles, and bridge deck panels. The test members were subjected to environments simulating salt water and deicing agents for 370 days. Test results show that silica fume admixture prevents salt-induced corrosion of steel a reinforcing bar and tensioning strands.