dont reply to them, page-12

Ok so Silica Fume is apparently much cheaper to add to concrete.

I started reading this
http://www.silicafume.org/pdf/silicafume-users-manual.pdf

Hmm.  Silica Fume is cheap you say....
Google : "price of silica fume"

A disadvantage to utilizing silica fume in cement is the cost. Condensed silica fume costs from $400-$1,000/ton, which is significantly higher than portland cement ($90/ton).

So as much as a $1 per kg  and I am getting that you need to add between 7-11% Silica fume to achieve some pretty good benefits.  $1 per kg comes in around $50-$75 per tonne of concrete.  (These are really rough figures someone with time please correct me if I'm wrong).

I won't post this on the other thread but if someone confirms my assumptions and figures....