The influence of pluronic P123 micelles on corrosion behaviour of steel in cement extract and bulk matrix properties of cement paste

The influence of pluronic P123 micelles on corrosion behaviour of steel in cement extract and bulk matrix properties of cement paste

Koleva, D.A.
Denkova, A.G.
Hu, J.
van Breugel, K.

Civil Engineering and Geosciences

Structural Engineering

2012-12-31

The influence of Pluronic P123 (PEO20-PPO20-PEO70) micelles (of 10 nm size) on the corrosion behaviour of low carbon steel in cement extract (CE) was studied using electrochemical impedance spectroscopy (EIS) and potentio-dynamic polarisation (PDP). Additionally, mercury intrusion porosimetry (MIP) was emplo ed to derive the impact of admixed micelles on porosity and pore-size distribution of cement paste. The motivation for carrying out this investigation has two main aspects: first, previous studies on the effect of micelles in model solutions and reinforced mortar proved to be very promising; secondly, an upscale approach was sought in terms of costeffective polymer type. Previously studied was the influence of polyethylene oxide-bpolystyrene (PEO113-b-PS70) micelles (of 50 nm size) on steel corrosion resistance and microstructural properties of cement-based materials. It was concluded that a very low concentration of these PS-based micelles (0.024 g/l) added to CE results in an increased steel corrosion resistance. As far as cement-based matrix is concerned, significantly reduced porosity and permeability were recorded. Despite the positive results, two drawbacks appear with this application: on one hand the increase of corrosion resistance was isolated to early stages of treatment and no significant influence was observed later on. On the other hand, PEO-b-PS is a rather costly material, especially with regard to civil engineering applications. This work aimed to explore the possibility for using the significantly lower in cost and commercially available tri-block copolymer, Pluronic P123. The PEO20-PPO20-PEO70 micelles feature a PEO “shell” as well and the expectation therefore was to achieve similar to the previously recorded or improved performance in their presence. The results, however, show different trends of materials’ behaviour: as far as steel corrosion resistance is concerned, a positive effect was observed, initially denoted to the presence of the polymer itself, rather than the presence of micelles. There was no significant influence of the P123 micelles on cement-based microstructure. The P123 micelles were found to mainly affect the steel corrosion resistance in the presence of NaCl as corrosion inducing factor. The related phenomenon is that the P123 micelles tend to self-assemble only within higher ionic strength of the medium, when the critical micelle concentration is reduced i.e. at the hereby tested concentration of 0.024 g/l the control cases (and the solid cement paste specimens respectively) actually contain unimers, wher as the composition of the medium for the corroding (Cl- containing cases) leads to micelles self-assembly, which actually contributes to the observed positive effects.

http://resolver.tudelft.nl/uuid:9deec4ac-1d4d-4076-9e91-95a636b7533a

European Federation of Corrosion

European Corrosion Congress EUROCORR 2012, Istanbul, Turkey, 9-13 Sept. 2012

Institutional Repository

conference paper

(c) 2012 Koleva, D.A., Denkova, A.G., Hu, J., van Breugel, K.