Strength of porous glass in water

Abstract

Partially leached glass rods show a marked increase in strength when tested in water. The strengthening effect is due to development of compressive stresses in the constrained porous glass layer of such rods resulting from adsorption of water. Completely leached porous glass rods that have been abraded prior to testing in water recover some of their strength, the degree of recovery depending on the internal surface area, the chemical composition, and the temperature and acidity of the aqueous solutions in which they were aged prior to testing in the presence of water. The partial recovery of strength is attributed to crack blunting. The decrease in internal surface area that accompanies the strength increase of abraded high-surface area porous glass rods leads one to conclude that the partial recovery of strength observed on aging porous glass in hot water or dilute acid is associated with an increase in the crack-tip radius and structural changes of the porous glass itself.