Chloride Ion Penetration Into Blended Cement Pastes and Concrete

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Title: Chloride Ion Penetration Into Blended Cement Pastes and Concrete

Author(s): M. H. Decter, N. R. Short, C. L. Page, and D. D. Higgins

Publication: Special Publication

Volume: 114

Issue:

Appears on pages(s): 1399-1412

Keywords: blast furnace slag; blended cements; chlorides; concretes; corrosion; diffusion; Materials Research

Date: 5/1/1989

Abstract:
Penetration of chloride ions from the environment into reinforced concrete is important in relation to corrosion behavior of embedded steel. Blended cements containing ground granulated blast furnace slag (GGBFS) are expected to offer a greater degree of protection compared to that of OPC. The kinetics of chloride ion diffusion through hardened cement pastes made from SRPC, OPC, and OPC/GGBFS blends have been determined by a steady-state (thin disc) method. Concrete slabs containing similar cements and quartzite aggregate have been made and ponded regularly with 5 percent NaCl solution. Material taken from various depths within these slabs has been subjected to pore solution expression and analysis, and the concentration profiles of free and total chloride have been determined. Values of chloride diffusivity obtained by the steady-state method have been used to calculate the chloride concentration profiles expected when penetration is into a semi-infinite medium. Comparison between the two techniques shows the same general trends in relative performance of the various cements, but actual chloride concentrations, at a given depth, are greater in the concrete slabs. Results from total and free chloride measurements indicate that the chloride-binding capacity of slag cements exceeds that of OPC and SRPC.