Alkali silica and pozzolanic reactions in concrete. Part 1: Interpretation of published results and an hypothesis concerning the mechanism
✍ Scribed by S. Urhan
- Publisher
- Elsevier Science
- Year
- 1987
- Tongue
- English
- Weight
- 707 KB
- Volume
- 17
- Category
- Article
- ISSN
- 0008-8846
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✦ Synopsis
This paper presents an hypothesis on the mechanism of alkali silica and pozzolanic reactions in concrete based on the competition m~chanism of the kinetics of dissolution of siiica and that of crystallisation of CSH.With the contact of siliceous particles with cement soIution OH-, Ca ++ , Na +, K + are adsorbed on the silica surface. The adsorption of OH-provokes the dissolution of silicium atom on the silica surface. Ca ++ is adsorbed more strongly so first it reacts with dissolving silica to form CSH. If the rate of crystaIlisation of CSH is higher than that of dissolution of silica, CSH can be formed on the surface of silica and dissolution stops. Otherwise, dissolution goes on and K +, Na + can penetrate into the structure leading to the formation of alkali silicate geI. Expansion of concrete depends on the quantity and viscosity of alkali silicate gei produced, and on the mechanicai strengths and porosity of concrete. Influences of different parameters like pH of the solution fineness, quantity and type of silica, temperature are also discussed.