Alkali Activation of a Norwegian Granulated Blast-Furnace Slag

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Title: Alkali Activation of a Norwegian Granulated Blast-Furnace Slag

Author(s): Odd E. Gjorv

Publication: Special Publication

Volume: 114

Issue:

Appears on pages(s): 1501-1518

Keywords: activators; age-strength relation; alkalies; blast furnace slag; concretes; curing; fineness; heat of hydration; temperature; Materials Research

Date: 5/1/1989

Abstract:
Traditionally, the utilization of granulated blast-furnace slag (BFS) is based on activation with alkalies released from the hydration of portland cements (PC). In Finland, a special type of alkaline admixture was introduced some years ago for activation of BFS. In the present paper, some experiences based on the activation of a Norwegian BFS with this admixture are reported. To investigate the hydraulicity of the slag, the slag was ground to three different levels of Blaine fineness (420, 540, and 640 mý/kg) and hydrated at five different levels of curing temperature (20 to 60 C). For comparison, a Finnish slag and a Norwegian blended portland cement with 10 percent fly ash were also included in the test program. The test results demonstrate that increasing curing temperature and fineness of the slag significantly accelerate the strength development (more so at early ages than later on). Thus, at 60 C the slag with 640 mý/kg of fineness and a water-cement ratio of 0.33 reached a compressive strength of approximately 40 MPa after a curing period of 4 hr. After a curing period of 72 hr, the heat of hydration of the slag cements was only about 60 percent of that of the modified portland cement.