2009 – Post Tension Grout Corrosion Investigation

Bob Wark, Paul Hurst, Andy Peek

Current practice has been to use API Spec 10 Class G oilwell cement for the bond zone of post-tensioned ground anchors for dams. Historically, the concern had been that the use of AS 3972 Type GP cement and AS 1478 Type HWR water reducers (“superplasticisers”) would have adverse effects on the corrosion resistance of bare strand in the bond zone, due to additives present in some types of superplasticiser.

The superior fluidity of grouts using Type GP cement, together with the cement availability and potential economy, lead the authors to run accelerated corrosion tests based on the ASTM B117 Neutral Salt Spray Test, using sections of tendon embedded in a grout of Type GP cement and a modern superplasticiser alongside similar samples using Class G cement.

This paper describes the results from the testing, which indicate identical corrosion protection performance from both types of grout over a total of 5,000 hours exposure.

Keywords: Post-tensioned anchors, oilwell cement, superplasticisers, Type GP cement, corrosion protection

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