An investigation into the relationship between surface concrete resistivity and chloride conductivity test

The chloride conductivity test (CCT) is a South African-developed Durability Index (DI) test used for the evaluation and quantification of the quality of concrete cover. It is also used as an input parameter for service life prediction (SLP) of RC structures in the marine environment, using a modified version of Crank’s solution to Fick’s second law of diffusion. The surface concrete resistivity test is an electrochemical test that has a good correlation with the concrete chloride diffusion process. The surface concrete resistivity test is used as a quick way to determine the durability of concrete. The purpose of this study was to provide an in-depth literature review on surface concrete resistivity and investigate its use for the design and prediction of durability in RC structures. The study also compared and contrasted surface concrete resistivity with CCT, using results from previous work, in terms of their application in the design of RC structures. Thereafter, the study investigated the relationship between surface concrete resistivity and CCT. The study was carried out by comparing laboratory and field surface concrete resistivity with CCT results. Then, corrosion initiation periods (CIP’s) and diffusion coefficients were estimated using Mackechnie’s (1996) CCT SLP model as well as surface concrete resistivity models by Andrade (2004) and Baroghel-Bouny et al. (2009). Input parameters for the model such as surface concrete resistivity and CCT results were based on measurements from a previous study. It was found that moisture gradients, chloride contamination and temperature gradients easily influence concrete electrical resistivity testing done in-situ. The input parameters for the surface concrete resistivity models were restricted to laboratory results. The analysis revealed that for blended cement concrete, w/b ratio has a greater influence on chloride conductivity than binder type. It was observed that using a different binder type has a greater influence on surface concrete resistivity at a high w/b ratio than a low one. In addition, decreasing the w/b ratio for GGBS concrete is more effective than decreasing it for FA concrete in influencing the surface concrete resistivity. Andrade’s surface concrete resistivity SLP model resulted in similar CIP values as the CCT model for CEM I only concrete and slag concrete at 0.40 w/b. A constant links the diffusion coefficients from surface concrete resistivity and CCT models. An inverse relationship was found between surface concrete resistivity and the diffusion coefficient calculated from the CCT SLP model.

Grantor dc:publisher.institution

Department of Civil Engineering

Year dc:date.issued

2014

Author dc:creator

• Mutale, Lombe

Advisors dc:contributor.advisor

• Beushausen, Hans-Dieter
• Alexander, Mark Gavin
• Otieno, Mike

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/11427/9077

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/9077