Merantus, Stanley W.

The durability of Reinforced Concrete (RC) structures in the Marine environment is
causing serious concern in the structural infrastructure. Reinforced concrete structures,
exposed to aggressive environments, are expected to last with little or no maintenance for
long periods of time. However, one of the most serious environmental exposures that
causes degradation is Chloride Diffusion, due to shrinkage, atmospheric corrosion, and
tide-induced wet and dry conditions at the air-water interfaces of coastal structures.
Therefore, chloride diffusivity, which correlates with the electrical resistivity, has a
significant impact on the durability of concrete. Concrete chloride diffusivity has been
experimented by multiple agencies and researchers on sound concrete, but there is a
considerable need for investigation of the durability of cracked concrete in the marine
environment. The two test methods carried out are presented: Standardized American Society for Testing
and Materials (ASTM) C1202 for Rapid Chloride Permeability (RCP) and ASTM D257
for Surface Resistivity (SR), and Nordtest (NT) Build 492 for Rapid Chloride Migration
(RCM) and Bulk Resistivity (BR) for both sound (uncracked) and cracked (micro and
macro) concrete. The limitations of the ASTM method, due to measurements before the
steady-state migration is reached, does not account for leakage in cracked concrete, and the
heating of the specimen due to higher current that increase the conductivity are indicated.
The Rapid Chloride Migration test provides for the non-steady state of diffusion. Again,
Bulk Resistivity, in contradistinction to Surface Resistivity is more accurate for cracked
concrete. The correlation betweeen RCM-BR are plotted. Chloride Permeability/Migration
is an important parameter that governs the Durability of Concrete.
The principal contribution is the highlighting of the inadequacy of the current widely used
standard ASTM C1202 for diffusivity testing, and the need for revision with further
investigation.

The Durability of Reinforced Concrete (RC) structures in the Marine environment is causing increasingly serious concern in the structural infrastructures. RC structures, exposed to aggressive environments, are expected to last with little or no maintenance for long periods of time. However, one of the most serious environmental exposures that cause degradation is Chloride Diffusion, with tide-simulated wet and dry conditions at the air-water interface.

This investigation, jointly project with Cemex (a cement mixing company), will address the change of chloride diffusion current resistivity due to macro and micro cracking, which is inevitable in all concrete structures. The correlation of Chloride Diffusivity with Electrical Current Resistivity of Sound and Cracked Concrete is studied experimentally, and the results compared with Analytically Determined values.

The principal benefit of the research is the formulation of models to predict time-dependent Chloride Penetration into Sound and Cracked Concrete in the Marine environment.