Title: An Interpretation of Some Published Researches on the Alkali-Aggregate Reaction Part 1-The Chemical Reactions and Mechanism of Expansion

Author(s): T. C. Powers and H. H. Steinour

Publication: Journal Proceedings

Volume: 51

Issue: 2

Appears on pages(s): 497-516

Keywords: no keywords

DOI: 10.14359/11691

Date: 2/1/1955

Abstract:
Research results are interpreted as having the following indications: The relative reactivity of a given form of silica is determined by the number of in-terrupted silicon-oxygen-silicon linkages, a matter of specific surface and "holes" due to disorderly atomic arrangements. Caustic attack on reactive silica in the presence of excess lime produces a nonswelling lime-alkali-silica complex if chemical equilibrium is reached. In affected concrete some of this complex is produced, but abnormal swelling is due to the formation of an alkali-silica complex which is not in equilibrium with lime. The persistence of the nonequilibrium product appears to be due to the inability of lime to diffuse into the reactive particle where alkali-silica complex has formed. Ex-pansion of concrete is probably due primarily to the swelling of solid alkali-silica complex, but it may,also be due to hydraulic pressure generated by osmosis, or by both mechanisms.