The effects of specific surface area and dosages of grinding granulated blast furnace slag(GGBS) on strength of slag blend cement were investigated by weakening buffer operator and curve fitting.The results show that on the basis of the compressive strength of slag blend cement with different slag dosages

GGBS is divided into three categories: coarse slag powder with specific area below 400 m2/kg

fine slag powder with specific area from 450 m2/kg to 550 m2/kg and super-fine slag powder with specific area above 600 m2/kg.Its ratios of compressive strength with silicate cement one show decreasing

fluctuant and increasing trend respectively with the content of slag powder increasing.By contrasting mill time of slag powder and the strength increasing of slag blend cement

the optimum range of slag powder fineness

from 450 m2/kg to 550 m2/kg

was determined.