This indicates that the concrete used for your foundations will have portland cement as its only "cementitious" component. The majority of pre-mix concrete suppliers are able to supply their concrete with a "waste substitute" such as fly ash, or furnace slag - this can substantially reduce the embodied CO2 of the cement with relatively little impact on the physical characteristics of the concrete.
Click to open the following link in a new window (see above):
http://www.greenspec.co.uk/cement-substitutes.php