EXPERIMENTAL-MEASUREMENT OF THE KINETICS OF FORMATION OF A SILICON-CALCIUM GEL PRODUCED BY AN ALKALI-SILICA REACTION

The alkali-silica reaction (ASR) is an internal physical and chemical process that appears to be the cause of functional disorders observed in concrete structures. These disorders are attributable to the growth , in the limited porous space of concrete, of gels produced by those A SR. So the kinetics of formation of gel produced by the ASR is followe d by indirect method using the properties of silicate gels to exchange ions. The ASR properly so called is done under a closed system by mak ing an alkaline dissolution upon an opal in the presence of an excess of calcium hydroxide Ca(OH)(2), and an exchangeable cation, the stront ium. The main results are: The quantity of formed gel as a function of time corresponds with a kinetics of formation of gel constant and ver y quick under the experimental conditions chosen (25 and 38 degrees C) . The experimental results, at both temperatures, suit with the thermo dynamic approach used. (C) 1997 Elsevier Science Ltd.