Chloride Thresholds in Concrete

Within the Concrete Repair industry there are many views on the levels of Chlorides within concrete and the threshold limit that reduces the effects of corrosion inhibitors.

QED’s guidelines are that Margel will work in concrete with Chloride thresholds upto 3% by weight of cement as proven in testing and actual usage, we are sponsoring further tests to establish whether the Chloride limit has any bearing at all on the effectiveness of Margel at rates above 3%. We are aware of works were Margel has been used at rates between 3-4% with no reported issues.

We have tested effectiveness at different thresholds over the last 30 years;

1983 - Fawley Powerstation -  tested successfully at 3% by weight of cement

1990 - Geomaterials Testing - tested successfully at 2% by weight of cement

1990-93 - Bierrum Tests - tested successfully at 2% by weight of cement

2009 - Case study - used in concrete structure at peak levels of 0.367 % by weight of concrete (2.62% equiv) Installed in Churchill College, Cambridge, UK in July2009

2013 - Greece - SETPOINT - tested successfully at 0.34% by weight of concrete (approx 2.5% by wt cement)

2017 - Russia - tested successfully at 2% by weight of cement

Chloride Guidelines;

In order to calculate the total chlorides by weight of cement, a cement content of 14% by weight (i.e. a mix ratio of approximately 6:1 by weight) is used as recommended in BRE IP21/86.

It should be noted that BS5328: Part1 , Section 4,2,2; Table 4 tates that concrete containing embedded metal (and made with cement complying with BS12, BS146, BS1370, BS4246, BS6588, BS6610 or combinations with g.g.b.f.s or p.f.a) shall have a maximum total chloride content as CI of 0.4% by weight of cement.

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