My shoddy math says that's a reduction of about 4.5%. So...better than nothing, I guess.
1 tonne of concrete produces 150kg CO2e, 1m³ concrete =2.4 tonnes, so 360kg CO2e/m³.
16/360 = 4.5%
Which would have been a more helpful figure for the article to include.
http://www.greenrationbook.org.uk/re...ints-concrete/