Title: Characterization of Aged Slag Concretes

Author(s): Hua Xu, John L. Provis, Jannie S. J. van Deventer, and Pavel V. Krivenko

Publication: Materials Journal

Volume: 105

Issue: 2

Appears on pages(s): 131-139

Keywords: activation; alkali-activated slag concrete; characterization; durability.

DOI: 10.14359/19753

Date: 3/1/2008

Abstract:
Slag concretes, activated by carbonates or carbonate/hydroxide mixtures and cast between 1964 and 1982, are examined. These concretes have served for prolonged periods under conditions in which portland cements would have deteriorated rapidly, and yet have remained sound and actually increased in strength over their service life. By a combination of microscopic and nuclear magnetic resonance (NMR) analysis, this durability is attributed to the combination of a highly polymerized, relatively low-Ca, amorphous C-S-H outer product, with an inner product that undergoes continuing hydration via a cyclic process involving carbonate anions. The relatively consistent Ca/Si ratio across all phases is believed to contribute to durability, as is the low Al content of the C-S-H phases formed in systems using hydroxide activators. The low permeability of the concretes also appears to have contributed to their durability.