It appears to be not quite as strong as the gunite used for many repairs of that type. You can compare compressive strength (probably the main one for your columns) and other strength/elasticity/etc factors.
BASF N-425:
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http://www.buildingsystems.basf.com/p02 ... 25-tds.pdf Gunite:
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http://www.buildsite.com/pdf/fivestarpr ... 630310.pdf - (there are various strength mixtures gunite, above is just one of them)
You would need to go with what they are supplying at this time due to not having followed through on inspections of the project as it has progressed. If you make any changes to the specified product then you, not the engineer, becomes responsible for whether it works or not.