1.7—SpecificationsASTM C 989, first

1.7—Specifications
ASTM C 989, first adopted in 1982, provides for three strength grades of GGBF slags, depending on their respec- tive mortar strengths when blended with an equal mass of portland cement. The classifications are Grades 120, 100, and 80,* based on the slag-activity index expressed as:
SAI = slag-activity index, percent = (SP/P x 100)
SP = average compressive strength of slag-reference ce- ment mortar cubes, psi
P = average compressive strength of reference cement mortar cubes, psi
Classification is in accordance with Table 1.2 (adapted from ASTM C 989) as follows:
The slag-activity index test is influenced by the portland cement used; ASTM C 989 specifies total alkalies and 28- day compressive strengths for the reference cement. The pre- cision of this test is such that the coefficient of variation is
4.1 percent for single laboratory testing and 5.7 percent for multilaboratory testing.
In addition to requirements on strength performance, the specification limits the residue on a 45-m (No. 325) sieve to 20 percent and the air content of a mortar containing only GGBF slag to a maximum of 12 percent.
The specification also includes two chemical require- ments: one limiting the sulfide sulfur (S) to a maximum of
2.5 percent and the other limiting the sulfate content (report- ed as SO3) to a maximum of 4.0 percent.
Canadian standards CSA A363 and CSA A23.5 differen-
tiate between GGBF slags that react hydraulically with water and those that require activators to develop their cementi- tious properties quickly.
Blended cements, in which the GGBF slags are combined with portland cement, are covered by ASTM C 595. Three types of such cements are addressed: 1) slag-modified port- land cement [Type I (SM)], in which the GGBF slag constit- uent is less than 25 percent of the total mass; 2) portland blast-furnace slag cement (Type IS), which contains 25 to 70 percent GGBF slag; and 3) slag cement (Type S), containing