Vedalakshmi, R. and Rajagopal, K. and Palaniswamy, N. (2008) Longterm corrosion performance of rebar embedded in blended cement concrete under macro cell corrosion condition. Construction and Building Materials, 22 (3). pp. 186-199.

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Abstract

The concrete does not possess sufficient resistance towards the permeation of aggressive ions when it is exposed to marine environment. When mineral admixtures are added, they impart certain impermeability to concrete by improving the physical structure by pozzolanic reaction. The reduction of concentration of OH ion occurs either by consumption of free Ca(OH)2 by pozzolanic reaction or by dilution of cement alkalis due to replacement with mineral admixture. This causes a substantial reduction in the threshold value of chloride in mineral admixed concrete. In the present investigation, the corrosion resistance of rebar embedded in concrete made with Portland pozzolana cement (PPC), Portland slag cement (PSC) was studied for 847 days under macro cell corrosion condition with on comparison using ordinary Portland cement (OPC). Concrete having characteristic compressive strength of 20, 30 and 40 MPa were taken for evaluation. Potential and macro cell corrosion current were measured periodically and corrosion rates were determined by weight-loss method. This long term experiment revealed that in 20 MPa concrete, the corrosion rate of rebar in PPC and PSC concrete was 9 and 10 times lower than the rebar in OPC concrete: In the case of 30 MPa concrete, the corrosion rate of rebar in PPC and PSC concrete was 17 and 6 times lower respectively and in 40 MPa concrete it was 1.6–2.5 times less than the rebar in OPC concrete. The reduction of chloride ion content in blended cement concrete was varied from 1.4 to 3.1 times less than the OPC concrete among all the three concretes studied. Reduction of alkalinity in 20 MPa concrete at the rebar level in PPC and PSC concrete is 6 and 10 times lower, respectively, than in OPC concrete. In the case of 30 and 40 MPa concrete it was 2 and 1.6 times lower. The reduction in alkalinity did not accelerate the corrosion rate of rebar in blended cement concretes even in presence of higher amount of chlorides. The apparent chloride diffusion co-efficient of blended cement concretes was 1.6–1.8 times lower than that of OPC concrete. The combined effect of higher chloride complexing ability and reduction of chloride ion diffusivity of blended cement concretes made them to perform better in terms of corrosion protection of reinforcing steel.

Item Type:	Article
Uncontrolled Keywords:	Blended cements; Macro cell corrosion; Corrosion rate; Chloride diffusion co-efficient; Pozzolanic reaction
Subjects:	Corrosion Protection Corrosion Science and Engineering
Divisions:	UNSPECIFIED
Depositing User:	ttbdu cecri
Date Deposited:	16 Jan 2012 15:53
Last Modified:	16 Jan 2012 15:53
URI:	http://cecri.csircentral.net/id/eprint/53

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